small buildings structural guidance

domestic structure SBSG 2007

ANNEX C Small buildings structural guidance 1.A General 1.B Stability 1.C Foundations 1.D Masonry walls 1.E Timber frame walls 1.F Timber floor and roof members

contents

domestic structure SBSG annex 1.A 2007


Annex 1.A General 1.A.0 Introduction 1.A.1 Scope 1.A.2 Revisions to small buildings guide 1.A.3 New guidance 1.A.4 Explanation of terms 1.A.5 Rules of measurement for storeys, walls , panels and building heights

Contents


annex

1.A General

1.A.0 Introduction The Small Buildings Structural Guidance (SBSG) which is contained within Annexes 1.A-F has been prepared to provide structural guidance to designers of small domestic buildings on how to meet Standard 1.1.

The buildings covered by this guidance are restricted in terms of construction type, size and subsoil conditions to those commonly occurring in Scotland.

This guidance has been written for those with expertise in building design and construction but not necessarily in structural engineering design. Where the conditions or parameters fall outside the scope then specialist advice should be sought from chartered engineers with the appropriate skills and experience.

This guidance replaces the Small Buildings Guide Second Edition 1994 and has been prepared in consultation with ODPM and DFP Northern Ireland so that reasonably uniform solutions might be adopted towards meeting the requirements of the respective structural regulations and to incorporate a broader base of experience into the definition of standards.

1.A.1 Scope This guidance covers the following types of buildings- a. Buildings with masonry walls

• domestic buildings of not more than 3 storeys without basement storeys • extensions with eaves height not more than 3m to low rise domestic buildings including

garages and outbuildings; • single storey, single skin buildings forming a garage or outbuilding within the curtilage of a

dwelling

b. Buildings with timber frame walls • domestic buildings of not more than 2 storeys without basement storeys • extensions with eaves height not more than 3m to low rise domestic buildings

The full description of the types of buildings and restrictions to which this guidance is applicable is set out within the scope of each of the annexes.

It recommended that prior to using the SBSG for particular works , the scope of the works should be checked against all of the limitations on its use to ensure that it is appropriate in the circumstances .and in particular : Annex 1C: Foundations : Geotechnical conditions Annex 1D: Masonry walls : Not more than 3 storeys Maximum building height of 15 m Maximum 12m length between supporting walls Wind speed verses the allowable height of building Openings in walls not more than 3 m in length Annex 1.E: Timber frame walls Not more than 2 storeys Maximum building height of 10 m Maximum 10m length between supporting walls Wind speed verses the allowable height of building Openings in walls totalling not more than 30% of the wall area Annex 1F: Timber floor and roof members Floor spans not exceeding 5.4 m Roof spans not exceeding 6 m Raised Tie and Collared Roofs only for attic storage loading


Design and construction will also have to comply with all other relevant building standards

Annex 1.B gives general rules on stability which should be observed in Annexes 1.E-F whereas Annexes 1.C and 1.E -F should not be used independently of each other.

1.A.2 Revisions to Small Buildings Guide The Small Buildings Guide has been revised and updated to Small Buildings Structural Guidance incorporating changes in construction practice specifically; Loadings • ‘Wind loading on traditional dwellings ‘Proposed revision of the simplified roof snow load map for Scotland Masonry walls • More detailed guidance on openings • More detailed guidance on lateral support • Differences in ground levels either sides of walls • Stainless steel wall ties to be used in all locations Timber Floor and Roof Members The timber span tables have been expanded to cover raised tie and collared roofs. 1.A.3 Timber frame construction Timber frame construction has been a significant form of construction for domestic buildings for over 20 years in Scotland ,rising from 38% of new starts in 1984 in the volume housing market to over 63 % in 2004, and a large proportion of the single build and extension market. Although the guidance in the Small Buildings Guide was restricted to traditional masonry construction as timber frame construction has been used and accepted for over 30 years it was considered necessary to extend the scope of the guidance for small buildings to include timber frame walls.

The timber frame wall guidance has been restricted to masonry clad platform frame construction which is the most common form of construction. 1.A.4 Explanation of Terms The following terms are used in the SBSG in addition to the definitions and explanation of terms in Appendix A of the Technical Handbooks. Buttressing wall means a wall designed and constructed to afford lateral support to another wall perpendicular to it, support being provided from the base to the top of the wall. Cavity width means the horizontal distance between the two leaves of a cavity wall. Pier means a member which forms an integral part of a wall, in the form of a thickened section at intervals along the wall so as to afford lateral support to the wall to which it is bonded or securely tied. Spacing means the distance between the longitudinal centres of any two adjacent timber members of the same type, measured in the plane of floor, ceiling or roof structure of which the members form a part. Span means distance measured along the centre line of a member between the centres of any two adjacent bearings or supports. Note: The spans given in Annex 1.E for Cripple Studs and Lintels and in Annex 1.F for floor joists, and roof joists are the clear spans, i.e. spans between the faces of the supports. Supported wall means a wall to which lateral support is afforded by a combination of buttressing walls, piers or chimneys acting in conjunction with floors or roof. Engineered fill means fill that is selected, placed and compacted to an appropriate specification in order that it will exhibit the required engineering behaviour .Normally such fill would not have taken place prior to development of the site allowing the necessary control over the type of fill material and method of placement to be exercised. Non-engineered fill means fill that has arisen as a by-product of human activity, usually involving the disposal of waste materials. Normally such fill would occur on sites where uncontrolled filling has taken place and therefore no reliance can be placed on the type of fill material and method of placement and hence its ability to support the buildings.


1.A.5 Rules of measurement for storeys , walls , panels and building heights The height of a wall or a storey should be measured in accordance with the following diagram.

H3H2

H1

line of lateral support to gable at ceiling levelunderside

ofroof joist

2.7m

max

2.7m maxTop of foundations

H P

AA1

=

line of base of gable

B

D

C B1 top of wall or base of parapet

parapet=

line of top of gable

line of lateralsupport to gable

wall along roof slope

=

=

2.7m

max

2.7m

max

base of wall

ground level

Pane

l hei

ght

Floor deck thickness

head

bin

der

thic

knes

s

Pane

l hei

ght

floor deck thickness

panel height

floor joist panel height

Key (a) Measuring storey heights A is the ground storey height if the ground floor is a suspended timber floor or a structurally separate ground floor slab A1 is the ground storey height if the ground floor is a suspended concrete floor bearing on the external wall B is the intermediate storey height providing B1 is the top storey height for walls which do not include a gable C is the top storey height where lateral support is given to the gable at both ceiling level and along the roof slope D is the top storey height for walls which include a gable where lateral support is given to the gable only along the roof slope (b) Measuring wall heights H1 is the height of a wall that does not include a gable H2 is the height of a compartment or a separating wall which may extend to the under side of the roof. H3 is the height for a wall(except a compartment or separating wall) which includes a gable P is the height of a parapet. If the parapet height is more than 1.2m add the height to H1

(c) Measuring timber panel heights Panel heights are measured from the underside of the bottom rail to the top of the top rail (d) Measuring building height Building heights are measured from the lowest finished ground level to the highest point of the roof

domestic structure SBSG annex 1.B 2007

Annex 1.B Stability 1.B.0 Introduction 1.B.1 Stability recommendations 1.B.2 Timber roof bracing

Contents

domestic structure SBSG annex 1.B 2007

annex

1.B Basic requirements for stability

1.B.0 Introduction Buildings should be stable under the likely combinations of dead , imposed and wind loading conditions in terms of the individual structural elements , their interaction together and overall stability as a structure . This Annex provides guidance on the principles of stability and provisions which should be taken with respect to all forms of buildings within the scope of the SBSG. 1.B.1 Stability recommendations The following provisions should be made to ensure the stability of the building : a. the overall size and proportioning of the building should be limited in accordance with the specific

guidance for each form of construction; b. a suitable layout of walls (both internal and external) forming a robust three dimensional box

structure in plan should be constructed with restrictions on the maximum size of cells measured in accordance with the specific guidance for each form of construction;

c. the internal and external walls should be adequately connected by either masonry bonding or by using mechanical connections;

d. the intermediate floors and roof should be of such construction and interconnection with the walls that they provide local support to the walls and also act as horizontal diaphragms capable of transferring the wind forces to buttressing elements of the building.

More detailed guidance is provided in Annexes 1.B-1.E

1.B.2 Timber roof bracing Trussed rafter roofs should be braced in accordance with the recommendations of BS 5268: Part 3: 1998 . A traditional cut timber roof (i.e. using rafters, purlins and ceiling joists) generally has sufficient built-in resistance to instability and wind forces (e.g. from either hipped ends, tiling battens, rigid sarking, or the like). However, diagonal rafter bracing equivalent to that recommended in BS 5268: Part 3: 1998 or Annex H of BS 8103: Part 3: 1996 for trussed rafter roofs, should be provided particularly for single-hipped and non-hipped roofs of more than 40˚ pitch to detached houses.

domestic structure SBSG annex 1.C 2007

Annex 1.C Foundations 1.C.0 Introduction 1.C.1 Conditions related to the subsoil 1.C.2 Design recommendations 1.C.3 Eccentric foundations 1.C.4 Extensions to existing buildings 1.C.5 Minimum width of strip foundations

Contents


annex

1.C Foundations

1.C.0 Introduction The dead , imposed and live loads are transmitted from the building to the subsoil by means of the foundations which should be designed taking into account the loadings and the subsoil conditions without undue settlement . This Annex provides guidance on suitable subsoil conditions on which buildings within the scope of the SBSG can be constructed, the precautions to be taken and guidance on simple foundations for such buildings. 1.C.1 Conditions related to the subsoil The subsoil conditions should be adequate where there is no - • non- engineered fill or wide variation in type of subsoil within the loaded area; or • peat within the loaded area; or • a weaker type of soil within the loaded area at such a depth below the soil on which the foundation

rests as could impair the stability of the building The minimum depth to the underside of foundations should be determined on the basis of the greatest of: • the depth to selected bearing stratum; • a depth of 450 mm to the underside of foundations .This should avoid damage from frost action in

normal soil conditions although this depth may have to be increased in areas which are subject to long periods of frost or in order to transfer the loading onto satisfactory ground.

• depth of 600 mm to the underside of foundations where clay soils are present although this depth will commonly need to be increased in order to transfer the loading onto satisfactory ground.

The susceptibility of ground to movement, action of frost and changes in water table varies widely and the advice of a structural engineer should be sought if the conditions are outwith the parameters set out above. More detailed guidance is provided in BRE Digests 240 and 241. 1.C.2 Design recommendations The design of foundations should be adequate where all of the following are followed - a. the foundations are situated centrally under the wall( except as in clause 1.C.3); b. the strip foundations have the minimum widths given in the table to 1.C.5; c. concrete in chemically non-aggressive soils is composed of Portland Cement to BS EN 197-1 & 2:

2000 and fine and coarse aggregate conforms to BS EN 12620:2002 and the mix complies with one of the following recommendations: • in proportion of 50 kg of Portland cement to not more than 100kg (0.05m3) of fine aggregate and 200 kg (0.1m3) of coarse aggregate, or • Grade ST2 or Grade GEN I concrete to BS 8500-2

d. in chemically aggressive soils guidance is provided in BS 8500-1: Part 1 and BRE Special Digest 1. e. For strip foundations, the foundation width should not be less than the appropriate dimension , WF in table to 1.C.5


f. the minimum thickness, T, of the concrete foundation is 150 mm or the scarcement width, P; whichever is the greater, where P is derived using the table to 1.C.5 and the diagram below. Trench fill foundations may be used as an acceptable alternative to strip foundations.

g. footings with regular offsets should have a depth at least 1.33 times the respective projection P1 (see diagram 1.7.2 opposite); with the overall width not less than the sum of , WF from table to 1.C.5 plus offset dimensions A1 and A2 and walls should be central on the foundation

h. for foundations stepped in elevation • height of steps, S, should not be of greater height than the foundation thickness, T • overlap, L, should be the greater of twice the step height ,S, the foundation thickness, T, or 300

mm

. ..

P P

.

T

WT

WF

..

.

T

PP A1 WT A2

P1

1.33 P min1

W + A + AF 1 2

L

L = greater of 2 x S, T, 300mm

S

T

i. and chimneys should project as shown in the diagram below where X must be not less than P

foundations for piers , buttresses

XX

X

P


1.C.3 Eccentric foundations a. This guidance and the diagram opposite is limited to:

• single storey buildings of 4.5 m maximum height where a wall is to be constructed either against a boundary or against an existing wall where it is not possible to construct the wall centrally on the foundation.

• masonry cavity or timber frame walls with masonry outer leaf with either a flat or pitched roof

• similar good ground conditions below both the existing and new foundations

• the foundations should comply with all of the clauses of this Annex (i.e. minimum foundation depth thickness and width ,concrete grade (Grade ST2 or GEN I) and the range of normal subsoil conditions stated) .

b. Where the wall and its foundation is to be constructed against an existing wall then the foundation should comply with 1.C. 4 below

c. the full width of the foundation, WF (from Table 1.C.5) is

not effective in transmitting the load to the soil, and only a proportion of the width is effective. This effective width of the foundation, WF' is determined from WF' = WF – (2 × e) where e is the eccentricity of the resultant thrust R due to the wall load, about the centre-line of the foundation.

d. Nonetheless, the minimum foundation width,WF, should still be read directly from Table 1.C.5.

e. the minimum foundation thickness, T for the minimum foundation widths listed in Table 1.C.5 should be taken as 200mm.

f. an appropriate steel reinforcement mesh, (e.g. A142), should be placed at 50mm cover from the base of the foundation.

.

WT

e

R

WF'

WF

T


1.C.4 Extensions to existing buildings a. This guidance and the diagram opposite is limited to:

• extensions of not more than two storeys connected to existing buildings

• extensions with masonry cavity or timber frame walls with masonry outer leaf with either a flat or pitched roof

• similar ground conditions below both the existing and new foundations in range types I-VI from Table to 1.C.5

• the extension foundations should comply with all of the clauses of this Annex (i.e. minimum foundation depth thickness and width ,concrete grade (Grade ST2 or GEN I) and the range of normal subsoil conditions stated) .

b. Where the depth of the existing foundations is less than that in 1.C.1, the depth of the extension foundation should match that of existing foundation depth at the interface and step down progressively to that of 1.C.1.

e. To minimise the occurrence of differential settlement between the extension and the existing structure, the following should be considered; • movement joints should be placed between the existing

and new foundations, and walls to accommodate any differential settlement between the extension and existing building .

• on non-compressible soils and rock (Soil types I, II and III in Table 1.C.5) the strip foundation widths listed in the table should be adopted and the new foundation should be placed at the same depth as the existing foundation,

• On soils of medium compressibility (Soil types IV, V and VI in Table 1.C.5) the foundation dimensions should be large enough so that excessive settlement is avoided by increasing the minimum width ,WF, by 25% from the values listed in Table 1.C.5 to lower the bearing pressure on the soil, recognising that foundations on soil types V and VI do not fall within the provisions of this annex if the total load exceeds 30 kN/m.

• To reach less compressible soil, the new foundation may be placed at a greater depth than the existing foundation. In such a case extreme care must be taken to ensure that stability of the existing foundation is maintained during excavation for the new foundation.

• The design of an appropriate foundation on highly compressible soils (Soil type VII in Table 1.C.5) is beyond the scope of this annex and specialist advice should be sought for such cases.

• Additional information is provided in BRE GBG 53 Foundations for low-rise building extensions

• Where the subsoil to the existing building has been subjected to ground improvement techniques ( e.g. vibrocompaction , underpinning , soil replacement etc ) then specialist advice should be sought from chartered engineers with the appropriate skills and experience.

existing walls

new wall

movement joint between existing and new wallsand foundations

new foundation for extension

existing foundation

floor

existing wall

movement joint

new wall

Existing WallNew Walls

Brick ties and channels allowing vertical movement


1.C.5 Minimum width of strip foundations The recommended widths of foundations set out in the table below may be used subject to : • the subsoil conditions in 1.C.1, • the foundation design provisions in 1.C.2 • the type and condition of subsoil is known and is within the types set out in the Table below, • the loading at the base of the wall is within acceptable limits. The table is applicable only within the strict terms of the criteria described within it and where the subsoil is not covered by the types set out below or the total load from the load-bearing walling exceeds 70kN/linear metre or 30kN/linear metre in types of subsoil under heads V-VI or type VII subsoil below, then a designed foundation may be required and the advice of a structural engineer should be sought. Minimum width of strip footings Total load of load-bearing walling not

more than (kN/linear metre) 20 30 40 50 60 70 Type of

Ground (including engineered fill)

Condition of ground

Field Test Applicable Minimum width of strip foundation, WF (mm)

I Rock Not inferior to sandstone,limestone or firm chalk

Requires at least a pneumatic or other mechanically operated pick for excavation

In each case equal to the width of wall

II Gravel or Sand

Medium dense

Requires pick for excavation. Wooden peg 50mm square in cross section hard to drive beyond 150mm

250 300 400 500 600 650

III Clay Sandy Clay

Stiff Stiff

Can be indented slightly by thumb

250 300 400 500 600 650

IV Clay Sandy Clay

Firm Firm

Thumb makes impression easily

300 350 450 600 750 850

V Sand Silty sand Clayey sand

Loose Loose Loose

Can be excavated with a spade. Wooden peg 50mm square in cross section can be easily driven

400 600

VI Silt Clay Sandy clay Clay or silt

Soft Soft Soft Soft

Finger pushed in up to 10mm 450 650

Note Foundations on soil types V and V1 do not fall within the provisions of this annex if the total load exceeds 30kN/m.

VII Silt Clay Sandy clay Clay or silt

Very soft Very soft Very soft Very soft

Finger easily pushed in up to 25mm

Refer to specialist advice

domestic structure SBSG annex 1.D 2007

Annex 1.D Masonry walls

1.D.0 Introduction 1.D.1 Wall types 1.D.2 Conditions relating to the Building of which the walls forms part 1.D.3 Maximum floor area 1.D.4 Imposed loads on roofs , floors and ceilings Thickness of walls 1.D.5 General 1.D.6

Solid external walls, compartment walls and separating walls in coursed brickwork or blockwork

1.D.7 Solid external walls, compartment walls and separating walls in uncoursed stone , flints etc

1.D.8 Cavity walls in coursed brickwork and blockwork 1.D.9 Walls providing vertical support to other walls 1.D.10 Internal load-bearing walls in brickwork or blockwork 1.D.11 Parapet walls 1.D.12 Single leaf external walls 1.D.13 Modular bricks and bricks 1.D.14 Maximum height of buildings based on wind loadings 1.D.15 Maximum allowable length and height of the wall Construction materials and workmanship 1.D.16 Wall ties 1.D.17 Brick and block construction 1.D.18 Compressive strength of masonry units 1.D.19 Declared compressive strength of masonry units 1.D.20 Normalised compressive strength of masonry units 1.D.21 Compressive strength of masonry units in walls 1.D.22 Mortar 1.D.23 Lintels for openings Loading on walls 1.D.24 Maximum span of floors 1.D.25 Other loading conditions End restraint 1.D.26 Vertical lateral restraint to walls 1.D.27 Criteria for buttressing walls 1.D.28 Criteria for piers and chimney providing restraint Openings , recesses , chases and overhangs 1.D.29 General 1.D.30 Dimensional criteria for openings and recesses 1.D.31 Sizes of openings and recesses 1.D.32 Chases 1.D.33 Overhangs 1.D.34 Lateral support by roofs and buildings 1.D.35 Gable wall strapping 1.D.36 Interruption of lateral support 1.D.37 Movement in masonry Small single storey , single skin buildings 1.D.38 General 1.D.39 Size and proportions of openings 1.D.40 Wall thicknesses and piers 1.D.41 Horizontal lateral restraint at roof level 1.D.42 Proportions for masonry chimneys

Contents


annex

1.D Masonry walls

1.D.0 Introduction Small buildings of traditional masonry walls can be designed to take advantage of custom and practice to provide designs taking into account loading conditions , limitations on dimensions , openings and subject to , restraint conditions . This Annex provides guidance for traditional masonry wall construction for the following building types a. domestic buildings of not more than 3 storeys where loading criteria for individual floors does not

exceed those given in 1.D.4 and total limit of loading does not exceed that given in 1.D.25; b. single storey single skin extensions to domestic buildings including garages and outbuildings that

do not exceed the dimensional criteria set out in 1.D.2b ; and. d. single storey , single skin buildings forming a garage or outbuilding within the curtilage of a dwelling that do not exceed the dimensional criteria set out in 1.D.2c

1.D.1 Wall types This Annex deals only with the types of wall extending to full storey height set out below and parapet walls. a. Domestic buildings of up to 3 storeys

• External walls • Internal load bearing walls • Separating walls

b. Extensions to domestic buildings and single storey buildings • External walls • Internal load bearing walls

This annex should be used in conjunction with Annexes 1.B ;and a. if wall thickness is to be determined according to 1.D.5 to 1.D.13 all appropriate design conditions given in this Annex should be satisfied; b. walls should comply with the relevant requirements of BS 5628: Part 3: 2001, except as regards the conditions given in 1.D.2 and 1.D. 3 -4,1.D.14-41; c. in formulating the guidance of this Annex, the worst combination of circumstances likely to arise was taken into account. d. If a requirement of this Annex is considered too onerous in a particular case then adequacy by calculation should be shown in respect of the aspect of the wall which is subject to the departure rather than for the entire wall; e. the guidance given in this Annex is based upon unit compressive strengths of bricks and blocks being not less than that indicated in the Tables to 1.D.19-20 and diagrams to 1.D.21 f. BS5628 Part 1; 1992 gives design strengths for walls where the suitability for use of masonry units of other compressive strengths are being considered.


1.D.2 Conditions relating to the Building of which the walls forms part This Annex applies only to buildings having proportions within the following limits and as shown on the Diagrams below subject to the limits of 1.D.15 a. domestic buildings of not more than three storeys

• the maximum height of the building measured from the lowest finished ground level adjoining the building to the highest point of any wall or roof should not be greater than 15 m ;

• the height of the building H, should not exceed twice the least width of the building W1,

• the height of the wing H2 should not exceed twice the least width of the wing W2 when the projection P exceeds twice the width W2.

H not to exceed15m

lowest ground level

Maximum height

H

Minimum width

W1

H

W1 not to be lessthan 0.5H

W1

H2

W2W1

P1

b. Size of extensions to domestic buildings For extensions, height H should not exceed the relevant limits shown below (see also 1.D.38) where H is measured from the top of the foundation or from the underside of the floor slab where this provides effective lateral restraint.


Maximum roofslope 40

domestic building

3.0m

max

Domesticbuilding

extension

4.5m

max

==

3.0

m m

ax

c. Size of single storey , single skin buildings Small single-storey , single skin buildings the height H of the building should not exceed 3m and W (the length or width whichever is more ) shall not exceed 9m (see also 1.D.38) where H is measured from the top of the foundation or from the underside of the floor slab where this provides effective lateral restraint

3.0

m m

ax

3.0

m m

ax

Maximum roofslope 40

IIII

3.6

m m

ax

1.D.3 Maximum floor area

he guidance in this annex applies where - 1. Floors enclosed by structural walls on all side do not exceed 70 m2; and

d 36 m2

Ts

floors without a structural wall on one side do not excee


Area not exceeding 36 m 2







1.D.4 Imposed loads on roofs , floors and ceilings The imposed loads on roofs, floors and ceilings should not exceed those given in the table below.

Element Loading

Roof distributed load: 1.00 kN/m2 for spans up to 12 metres

1.50 kN/m2 for spans up to 6 metres

Floors distributed load: 2.00kN/m2 together with a concentrated load of 1.4 kN

Ceilings distributed load: 0.25 kN/m2 together with concentrated load: 0.9 kN

The guidance for snow loading in 1.F.6 applies only to a free standing flat roofed structure with no parapet and with the roof on one level only, provided that there are no other buildings within 1.5m of its perimeter.


Thickness of walls 1.D.5 General Wall thickness should be determined according to this Annex provided the following conditions are met- a. relating to the building of which the wall forms a part in 1.D.2-4 and 1.D.14 (3.4 , 3.15 to 3.17);

and b. relating to the wall in 1.D.15-41 (3.18 to 3.41). Wall thicknesses may be affected by adequate bearing for precast concrete units.

Conditions – building a. limitations on size and proportions of building and parts of building ( 1.D.2 ) b. max allowable floor areas ( 1.D.3) c. max imposed and wind loads ( 1.D.4 and 1.D.14)

Conditions relating to building of which wall forms part

Are building conditions satisfied?

Outside Annex1.D scope

Outside Annex 1.D scope

N

Conditions – wall a. max allowable length and height of wall ( 1.D.15) b. construction materials and workmanship ( 1.D.16-23) c. loading on walls ( 1.D.24-25) d. end restraints ( 1.D.26-28) e. openings , recesses ,

overhangs, chases (1.D.29-33)

f. lateral support by floors and roofs (1.D.34-36)

g. movement in masonry (1.D.37) h. conditions relating to external

walls of small single storey buildings and extensions ( 1.D.38-41)

Use 1.D.6-13 for wall thickness assessment

Yes

Conditions relating to wall

Yes

Are wall conditions satisfied ?


1.D.6 Solid external walls, compartment walls and separating walls in coursed brickwork or

blockwork Solid walls constructed of coursed brickwork or blockwork should be at least as thick as 1/16 of the storey height. Further requirements are given in the table below. Height of wall Length of wall Minimum thickness of wall not exceeding 3.5m

not exceeding 12m 190mm for the whole of its height

not exceeding 9m 190mm for the whole of its height exceeding 3.5m but not exceeding 9m exceeding 9m but not

exceeding 12m 290mm from the base for the height of one storey, and 190mm for the rest of its height

not exceeding 9m but not exceeding 12m

290mm from the base for the height of one storey, and 190mm for the rest of its height

exceeding 9m but not exceeding 12m exceeding 9m but not

exceeding 12m 290mm from the base for the height of two storeys, and 190mm for the rest of its height.

1.D.7 Solid external walls, compartment walls and separating walls in uncoursed stone, flints etc The thickness of walls constructed in uncoursed stone or bricks or other burnt or vitrified material should not be less than 1.33 times the thickness required by 1.D.6. 1.D.8 Cavity walls in coursed brickwork and blockwork All cavity walls should have leaves at least 90 mm thick and structural cavities at least 50 mm wide. The wall ties should have a horizontal spacing of 900mm and a vertical spacing of 450mm, which is equivalent to 2.5 ties per square metre. Wall ties should also be provided, spaced not more than 300mm apart vertically, within a distance of 225mm from the vertical edges of all openings, movement joints and roof verges. For selection of wall ties for use in a range of cavity widths refer to Table to 1.D.16. For specification of cavity wall ties refer to paragraph 1.D.16. For external walls, compartment walls and separating walls in cavity construction, the combined thickness of the two leaves plus 10 mm should not be less than the thickness required by 1.D.6 for a solid wall of the same height and length. 1.D.9 Walls providing vertical support to other walls Irrespective of the materials used in the construction, a wall should not be less in thickness than any part of the wall to which it gives vertical support. 1.D.10 Internal loadbearing walls in brickwork or blockwork With the exception of compartment walls or separating walls internal loadbearing walls should have a thickness not less than : (specified thickness from 1.D.6) /2 less 5 mm except for a wall in the lowest storey of a three storey building carrying load from both upper storeys, which should have a thickness as determined by the above equation or 140 mm, whichever is the greater.


1.D.11 Parapet walls The minimum thickness and maximum height of parapet walls should be as given in the table and diagrams below only where access is limited ( e.g. for occasional maintenance ). Cavity wall Max parapet height H (mm)

Thickness(mm)

600 t1+t2 not more than 200

860 t1+t2 more than 200

Solid wall

600 t = 150

760 t = 190

860 t = 215 Note that t must not be more than T

level of junctionof wall and structural roofT

t

Hp

t1

t2

level of junctionof wall and structural roof

1.D.12 Single leaf external walls The single leaf of external walls of small single storey non-domestic buildings and of extensions need be only 90 mm thick, provided the requirements of 1.D.38-41 are met.

1.D.13 Modular bricks and blocks Where walls are constructed of bricks or blocks having modular dimensions derived from BS 6649 -

985 wall thicknesses recommended in this Annex which derive from a dimension of a brick or block may be reduced by an amount not exceeding the deviation from work size permitted by a British Standard relating to equivalent sized bricks or blocks made of the same material.

1


1.D.14 Maximum height of buildings based on wind loadings The maximum height of building which should be adequate for the various site exposure conditions and wind speed should be derived by following the procedure which is set out on the Flow Chart below using the map of wind speeds , topographic zone diagrams below and tables 1 and 2 enabling the maximum height of building to be read off table 3 opposite This design guidance has been revised in accordance with Wind loading on Traditional dwellings and is based on BS 6399: Part 2 1997 using hourly mean wind speeds and it should be noted that the wind speeds are derived from a different basis than in the Small Buildings Guide and it is important that they are only applied to the methodology within this annex. Flow chart for deriving maximum allowable building height

Lu LuLu

Lu0.25LuLu0.4

Z2 Z1 Z2 Z3Wind di ection r

Lu

0.25 0.4 1.2

Hills and ridges

Map of wind speeds ( m/sec)

Z2 Z1 Z2Wind direction

0.4 Ld

0.4 Ld

Lu

0.4 Lu

0.4 Lu

Ld

Cliffs and escarpments

Topographic zones for Table 1

Read windspeed ,V from map above

Topographic zone from above diagrams

Read Factor ,T from Table 1

Factor A from table 2

Factor S = VxTxA

Max allowable building height from Table 3


Table 1 Factor T Table 2 Factor A

Factor T Site Altitude (m)

Factor A Topographic category and average slope of whole hillside, ridge, cliff or escarpment

Zone 1

Zone 2

Zone 3

Category 1: Nominally flat terrain, average slope < 1/20

1.0

1.0

1.0

Category 2: Moderately steep terrain, average slope < 1/5

1.24

1.13

1.10

Category 3: Steep terrain, average slope > 1/5

1.36 1.20 1.15

0

50 100 150 200 300 400

1.00 1.05 1.10 1.15 1.20 1.30 1.40

Note: Outside of these zones factor T = 1.0 Table 3 Maximum allowable building height (m)

Country Sites

Town Sitesa

Distance to the coastb

Distance to the coastb

Factor S

<10km 10 to 50km

>50km

<10km

10 to 50km

>50km

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

15 15 11 8 6

4.5 3.5 3

15 15

14.5 10.5 8.5 6.5 5 4

3.5 3

15 15 15 13 10 8 6 5 4

3.5 3

15 15 15 15 15

13.5 11 9 8 7 6 5 4 3

15 15 15 15 15 15 13 11 9.5 8.5 7.5 7 6

5.5 4.5 4 3

15 15 15 15 15 15

14.5 12.5 10.5 9.5 8.5 8 7 6

5.5 5 4 3

Notes a. For sites on the outskirts of towns not sheltered by other buildings use the values for country sites b. Where a site is nearer than 1 km to an inland area of water which extends more than 1 km in the

wind direction , the distance to the coast should be taken as from the edge of the water.


1.D.15 Maximum allowable length and height of the wall This annex does not deal with walls longer than 12 m, measured from centre to centre of buttressing walls, piers or chimneys providing restraint, or of walls exceeding 12 m in height. (See also table to 1.D.6 and 1.D.37 regarding movement joints ) Construction materials and workmanship 1.D.16 Wall ties Wall ties should comply with BS EN 845-1 and be material references 1 or 3 in BS EN 845 Table A1 austenitic stainless steel or suitable non-ferrous ties. Wall ties should be selected in accordance with the following table Cavity wall ties Permissible type of tie Normal cavity width (mm) (Note 1)

Tie length (mm) (Note 2)

BS EN 845-1 tie (Note 4)

50 to 75 200 76 to 90 225 91 to 100 225( Note 3)

Types 1, 2, 3 or 4 to DD 140-2* and selected on the basis of the design loading and design cavity width

101 to 125 250 126 to 150 275 151 to 175 300 176 to 300 (See Note 2)

*Although DD 140-2 was withdrawn on 1 February 2005, the tie user classes (types) given in Tables 1 and 3 of the latter document can continue to be used after this date.

Notes 1 Where face insulated blocks are used the cavity width should be measured from the face of the masonry unit. 2 The embedment depth of the tie should not be less than 50mm in both leaves. For cavities wider than 180mm calculate the length as the structural cavity width plus 125mm and select the nearest stock length. 3 Double triangle ties having a strength to satisfy Type 2 of DD 140-2*, are manufactured. Specialist tie manufacturers should be consulted if 225mm long double triangle format ties are needed for 91 to 100mm cavities. 4 Reference requires to be additionally made to DD 140-2* for the selection of the type (i.e. types 1, 2, 3 or 4) relevant to the performance levels given in DD140-2. 1.D.17 Brick and block construction Walls should be properly bonded and solidly put together with mortar. Materials should be chosen from the following list as being suitable for their intended use and for the exposure conditions, likely to prevail - a. clay bricks or blocks to BS 3921: 1985 or BS EN 771-1; or b. calcium silicate bricks to BS 187: 1978 or BS 6649: 1985; or BS EN 771-2 or c. concrete bricks or blocks to BS 6073: Part 1: 1981; or BS EN 771-3 or 4 or d. square dressed natural stone to the appropriate requirements described in BS 5628-3 or BS EN 771-6 ; or Manufactured Stone to BS 6457: 1984 or BS EN 771-5. 1.D.18 Compressive strength of masonry units The minimum compressive strength requirements for masonry units according to BS Standards and BS EN Standards are given in the Diagrams in 1.D.21 where the masonry units indicated for Conditions A, B and C should have declared compressive strengths of not less than the values given in the Table below. Normalised compressive strengths for block sized clay and calcium silicate masonry units not complying with brick dimensional format are given in the Table to 1.D.20.


1.D.19 Declared Compressive Strength of Masonry Units complying with BS EN 771 - 1 to 5 (N/mm2) Masonry Unit

Clay masonry units to BS EN 771-1

Calcium Silicate masonry units to BS EN 771-2

Aggregate Concrete Masonry Units to BS EN 771-3

Autoclaved aerated conc. Masonry units to BS EN 771-4

Manufactured Stone Masonry units to BS EN 771-5

Condition A Brick Group 1

6.0 Group 2

9.0 Group 1

6.0 Group 2

9.0

6.0 -

Block See clause 1.D.20 2.9* 2.9

Condition B Brick Group 1

9.0 Group 2

13.0 Group 1

9.0 Group 2

13.0

9.0 -

Block See clause 1.D.20 7.3* 7.3 Condition C Brick Group 1

18.0 Group 2

25.0 Group 1

18.0 Group 2

25.0

18.0 -

Block See clause 1.D.20 7.3* 7.3 Any

uni

t co

mpl

ying

with

BS

EN

77

1-5

will

be

ac

cept

able

fo

r co

nditi

ons

A, B

and

C

Notes 1. This table applies to Group 1 and Group 2 units. 2. For the EN 771 series of standards for masonry units the values of declared compressive strengths (N/mm2) are mean values. 3. Brick: a masonry unit having work sizes not more than 337.5 mm in length or 112.5 mm in height. 4. Block: a masonry unit exceeding either of the limiting work sizes of a brick and with a minimum height of 190mm. For blocks with smaller heights, excluding cuts or make up units, the strength requirements are as for brick except for solid external walls where the blocks should have a compressive strength at least equal to that shown for block for an inner leaf of a cavity wall in the same position. 5. Group 1 masonry units have not more than 25% formed voids (20% for frogged bricks). Group 2 masonry units have formed voids greater than 25%, but not more than 55% 6. Refer to 1.D.21 for locations of Conditions A, B and C 7. Values marked * are dry strengths to BS EN 772-1 1.D.20 Normalised compressive strength of masonry units of clay and calcium silicate blocks complying with BS EN 771 - 1 and 2 (N/mm2) Standard Condition Group 1 masonry units Group 2 masonry units

A 5.0 8.0

B 7.5 11.0

Clay masonry units to BS EN 771-1 Calcium silicate masonry units to BS EN 771-2 C 15.0 21.0

Notes: 1 Values in this Table are normalised compressive strengths (N/mm2). Compressive strengths of masonry units should be derived according to EN 772-1. 2 The Table applies to clay and calcium silicate block masonry units where the work size is more than 337.5mm in length or 112.5mm in height. 3 Group 1 masonry units have not more than 25% formed voids (20% for frogged bricks). Group 2 masonry units have formed voids greater than 25%, but not more than 55%.


1.D.21 Compressive strengths of masonry units in walls

Top of structural floor

underside of structural roof

HS

WhereH Less than or equal to

Condition A1m-

f

WhereH greater than

Condition B1m-

f

Underside of structural roof

Underside of structural floor

Cavity wall

Internal wall

Top of structuralfloor

Hf

S

S

This wall to be at least 140 mm thick in blockwork or 215 mm thick in brickwork below groundfloor level if height H exceeds 1m.f

Underside of structural floor

Topside of structural floor

Underside of structural roof

Cavity wall

This wall to be at least140mm thickblockwork or215mm thickbrickwork

Internal wall H S

H S

H S

Notes f H1. I .7 m , the compressive strength of bricks or blocks should be used in walls as

2. I ed in the wall should be at

3. I pressive strength of at

o determine strength of the masonry units where the roof construction is of timber.

indicated by the key

f H is more than 2.7m, the compressive strength of bricks or blocks us

S is not more than 2

S

least Condition B, or as indicated by the key whichever is the greater. f the external wall is solid construction the masonry units should have a comleast that shown for the internal leaf of a cavity wall in the same position.

The guidance in the diagram for walls of two or three storey buildings should only be used tthe compressive


1.D.22 Mortar Mortar should be - a. Mortar designation (iii) according to BS 5628:Part 3:2001;

c. 1:1: 5 or 6 CEM 1, lime and fine aggregate measured by volume of dry materials

with masonry cavity wall construction should be sted by a notified body or justified by calculations

l is 6 m, where the span is measured centre centre of bearing as shown on the diagrams below.

Wall joist hanger

b. Strength class M4 according to BS EN 998 - 2 ;

1.D.23 Lintels for openings Proprietary steel or concrete lintels suitable for usete Loading on walls 1.D.24 Maximum span of floors The maximum span for any floor supported by a walto Floor member bearing on Floor member bearing on

floor

floor spanmaximum 6m

centre line of bearing

floor

wall

floor spanmaximum 6m

centre line of bearing

Loading on walls 1.D.25 Other loading conditions a. Vertical loading on walls should be distributed. This may be assumed for concrete floor slabs, precast concrete floors, and timber floors designed in accordance with annex 1.F, and where bearing length for lintels is 150 mm or greater. Where a lintel has a clear span of 1200 mm or less

the

the wall and the combined dead and imposed

c. Walls should not be subject to lateral load other than from wind, and that covered by 1.D.25 b

the bearing length may be reduced to 100 mm. Where lintels carry a concrete floor the bearing length should be at least 150mm or L/10 whichever is the greater, where L is the span of the lintel.b. Differences in level of ground or other solid construction between one side of the wall and the other should be less than four times the thickness of load should not exceed 70kN/m at base of wall as shown below provided there is a full storey height of masonry above the upper retained level.


a. Examples of ground level differences

Ground Supportedfloor slab

Retained height

W

Suspended ground floor

Retained height

W

Void

t2t1

H should be lessthan or equal to1m and less than or equal to 4( + )t1 t2

W W

Suspended ground floor

Retained height

To be level fora distance of notless than 1.25H

mum differe l b. Maxi nces in ground leve

H

W

Retained height

W

Retained height

H

tH should be less than or equal to 1mand less than or equal to 4t

Concrete fillto wall cavity

t H should be less

and less than or

otes

ed for clarity and may be on either side of the walls shown.

ull storey height of masonry above

nt to walls t single leaf walls less than 2.5 m in height and length in small single

torey non-domestic buildings and extensions should be bonded or otherwise securely tied throughout their full height to a buttressing wall, pier or chimney. Long walls may be provided with intermediate support dividing the wall into distinct lengths; each distinct length is a supported wall for the purposes of this part. The buttressing wall, pier or chimney should provide support from the base to the full height of the wall.

than or equal to 1m

equal to 4t

NFloor slabs in diagrams b have been omittCavity walls should be tied in accordance with Table to clause 1.D.16. These recommendations apply only to circumstances where there is a fthe upper retained level. End restraint 1.D.26 Vertical lateral restraiThe ends of every wall, exceps


1.D.27 Criteria for buttressing walls

diagram below gives certain rules for bu itself a supported wall, its thickness T

The ionally i f the buttressing wall is not ld ot be less than - a. separating wall of similar height and

d does not exceed 6 m in total height and 10 m in c.

Not1. nded or

. The length, L , of the buttressing wall

3. d not impair the lateral support to

. Openings or recesses in the buttressing st

Openings in a buttressed wall

ttressing walls. Addit2 shou

half the thickness required by this part for an external or n

length, less 5 mm; or b. 75 mm if the wall forms part of a dwelling an

length; or 90 mm in any other case.

es The buttressing wall should be bosecurely tied to the supported wall and at the other end to a buttressing wall, pier or chimney.

2 B

should be at least 1/6 of the overall height, H, of the supported wall. The position and shape of the openings shoulbe given by the buttressing wall.

T2

550mm

Supported wall

H

4 wall more than 0.1 m2 should be at lea550mm from the supported wall.

LB

Buttressing

5. ot more than 0.1 m2 at any position. 6. should be not more than 0.9 times the floor to ceiling

g any masonry over the opening should be not less than 150

asuring the height of the supported wall. 1.Dpro1.

ys twice the thickness,

2. The sectional area on plan of chimneys (excluding openings for fireplaces and flues) should be not less than the area required for a pier in the same wall, and

required thickness of the

of the wall from base to top of wall.

Wall

There may be only one opening or recess nThe opening height in a buttressed wall height and the depth of lintel includinmm.

Refer to diagram to 1.A.5 for the rules for me

.28 Criteria for piers and chimney viding restraint Piers should measure at least three times the thickness of the supported wall, and chimnemeasured at right angles to the wall. Piers must have a minimum width of 190 mm as shown opposite.

the overall thickness should not be less than twice the supported wall

3. The buttressing wall, pier or chimney should provide support to the full height

min 190mm

H

T

centre line of buttressing wall

centre line of chimney

centre lineof pier

centre line ofpier(alternativearrangement)

Buttressing wall Pier

Chimney


Openings , recesses , chases and overhangs

The number, size and position of openings and r sses should not impair the stability of a wall or the lateral support afforded by a buttressing wall to a supported wall. Construction over openings and recesses should be adequately supported.

gs and reram and t grou

u a

1.D.29 General ece

1.D.30 Dimensional criteria for openin cesses

able below. The dimensional criteria are given in the diags belowNo openings should be provide in wall

n lnd floor except for small holes for services and m rea of 0.1 mve ti ation etc. which should be limited to a maxim

2 at not less than 2 m centres .

1.D.31 Sizes of openings and recesses

OpeningW1

OpeningW2

RecessW3 P4P3P2P1

OpeningW4

H

outer fa ofreturn w

corner of two external walls

ce all

P5

should n exceed 2L/3 . None of W1 or W2 or W3 should exceed 3m

e greater than W1/X reater than or equal to W1/X

7. P5 should be gre r th or eq l to W

but should not be less than 665 mm. 8. The value of Factor X should be taken from

the table below or can be given the value 6, th of the

the case of a cavity wall, .

wall into wall

Max Max Max Max

Notes 1. W1 + W2 + W3 ot 23. P1 should not b4. P2 should not be g5. P3 should be greater than or equal to (W2+ provided the compressive streng

W3)/X bricks or blocks (in6. P4 should be greater than or equal to W3/X in the loaded leaf) is not less than 7 N/mm

ate an ua 4/X

2

Value of factor 'X' (see diagram above)

Nature of ro Span of timber floor

into

Span of concrete floor

of span

Maximum roof span (m)

Minimum thickness of wall inner

Span of floor is parallel to wall

(mm)

4.5m 6.0m 4.5m 6.0m Value of factor 'X'

100 6 6 6 roof spans 6 6 parallel to wall non applicable

90 6 6 6 6 5

100 6 6 5 4 3 timber roof 9 spans into 6 3 wall 90 4 4 3


1.D.32 Chases Chases should not -

an 1/3 of wall thic ess or, in cavhan 1/6 of the thickness of the leaf or wall; and

mpair the stability of the wall, pa d. 1.D.33 Overhangs

ang, the amount of any projection should not impair the stability

the inte een diffe mpair the st all.

in clauses 1.D.34-35 . The requirements for lateral support of walls at roof and floor levels are given in the table below and guidance on satisfying the requirements is given in clauses 1.D35 and 1.D.36

Wall Type Wall Length Lateral support required

any length

roof lateral support by every roof forming a junction with the supported wall

a. if vertical, be deeper thb. if horizontal, be deeper t

kn ity walls, 1/3 of leaf thickness ;

c. be so positioned as to i rticularly where hollow blocks are use

In constructing a corbelled overhof the wall. Minor overhangs may occur atdifferences in thickness provided this does not i

rfaces betw rent masonry materials which have minorability of the w

1.D.34 Lateral support by roofs and floors The walls in each storey of a building should extend to the full height of that storey, and have horizontal lateral supports to restrict movement of the wall at right angles to its plane. Floors and roofs should - a. act to transfer lateral forces from walls to buttressing walls, piers or chimneys; and b. be secured to the supported wall by connections specified

Solid or cavity: external

compartment separating greater than 3 m

floor lateral support by every floor forming a junction with the supported wall

internal load-bearing wall

(not being a compartment or separating wall)

any length roof or floor lateral support at the top of each storey

Walls should be strapped to floors above ground level, at intervals not more than 2 m by tension traps as shown below to BS EN 845-1. For corrosion resistance purposes , the tension straps

16.1 or 16.2 (galv nised steel) or other more resistant c stainless steel). The declared tensile

sshould be material reference 14 or aspecifications including material references 1 or 3 (austenitstrength of tensions straps should not be less than 8 kN

i


30 x 5mm galvanised mildp

onry3 joists

Dwangs minimum 38mm width to extend at least ½ depth of joist

steel or other durable straheld tight against maswall and fixed across

30x5mm galvanised mild steel or other durable strapat least 1200mm long and held tight against masonry wall

internal leaf of external cavity wall requiring lateral restraint

Tension strap detail 1 Tension strap detail 2

Tension straps need not be provided -

a. in the longitudinal direction of joists in domestic buildings of not more than two storeys, if the joists are at not more than 1.2 m centres and have at least 90 mm bearing on the supported walls or 75mm bearing on a timber wall- plate at each end ,and

b. in the longitudinal direction of joists in domestic buildings of not more than two storeys, if the joists are carried on the supported wall by joist hangers in accordance with BS EN 845-1 of the restraint type described in BS 5628:Part 1 and shown opposite and are incorporated at not more than 2 m centres;

c. where a concrete floor has at least 90 mm bearing on the supported wall as opposite; d. where floors are at or about the same level on

each side of a supported wall and contact between the floors and wall is either continuous or at intervals not exceeding 2m. Where contact is intermittent, the points of contact should be in line or nearly in line on plan as shown on the diagrams below.

Restraint type joist hanger

X

X to be not less than 90mm

X

Restraint by concrete floor or roof

domestic structure SBSG annex 1.E 2007

Restraint of internal walls

Where joists are not hard up to the wall blockings at not greaterthan 2m centres should be used at the same locations on both sides of the wall

y tension straps as shown in the diagrams

at ing 2m if the roof -

by local experience to be

d. o the supported wall at not more than 1.2 m centr s. um of thickness

s + 10mm

Tension 1.D.35 Gable wall strapping

Gable walls should be strapped to roofs as shown opposite bopposite .

Vertical strapping at least 1m long should be providedeaves level at intervals not exceeda. has got a pitch of 150 or less; b. is not tiled or slated; c. is not of a type known resistant to wind gusts; and

has not got main timber members spanning ont

strapsst point If H is greater

Tension strapsat not more than 2 metre centres

Gableend wall

t

at highethat will provide a secure connection

than 16t, providerestraint here at not greater than 2m centres

e = s

of leave h

X X/2

X/2

Tension strap location

Effective strapping at gable Vertical strapping at eaves Vertical strapping at eaves

dwang

packStrap turnedover uncutblock

Rafter fixed to wall plate with framing anchor or truss clip

strap anchored to wall and rafter

Each joist fixed to wall-plateWith framing anchorsOr skew nails

Strap anchored towall and turned over wall plate


1.D.36 Interruption of lateral support Where a stair or other opening in a floor or roof adjoins a supported wall and interrupts the continuity of lateral support- a. the length of the opening should be not more than 3 m, measured parallel to the supported wall; b. where a connection is provided by means other than by anchor, this should be provided

throughout the length of each portion of the wall situated on each side of the opening; c. where connection is provided by anchors, these should be spaced closer than 2 m on each side

of the opening to provide the same number of anchors as if there were no opening; and d. there should be no other interruption of lateral support.

1.D.37 Movement in masonry Max spacing of movement joints Clay brickwork 12 m centres Calcium silicate brickwork 7.5 m centres Concrete brickwork and blockwork 6 m centres

Reference should be made to BS 8103-2, Annex B Code of practice for masonry walls for housing which provides general guidance for movement joints.


External walls of small single storey single skin buildings and extensions 1.D.38 General The guidance given applies in the following circumstances:- a. The floor area of the building or extension does not exceed 36m

2

b. The walls are solidly constructed in brickwork or blockwork using materials which comply with clauses 1.D.16-1.D.23. c. Where the floor area of the building or extension exceeds 10m

2 ,the walls have a mass of not less than 130 kg/m

2. (Note: There is no surface mass limitation recommended for floor areas of 10m

2 or

less.) d. Access to the roof is only for the purposes of maintenance and repair. e. The only lateral loads are wind loads. f. The maximum length or width of the building or extension does not exceed 9m. g. The height of the building or extension does not exceed the lower value derived from the Diagrams to clause 1.D.2. h. The roof is braced at rafter level, horizontally at eaves level and at the base of any gable by roof decking, rigid sarking or diagonal timber bracing, as appropriate, in accordance with BS 5268: Part 3. i. Walls are tied to the roof structure vertically and horizontally in accordance with clauses 1.D.34-36 and with horizontal lateral restraint at roof level in accordance with clause 1.D.41. j. The roof structure of an extension is secured to the structure of the main building at both rafter and eaves level. 1.D.39 Size and proportions of openings One or two major openings not more than 2.1m in height are permitted in one wall of the building or extension only. The width of a single opening or the combined width of two openings should not exceed 5m. The only other openings permitted in a building or extension are for windows and a single leaf door. The size and location of these openings should be in accordance with the diagram below. Notes 1. Major openings should be restricted to

one wall only. Their aggregate width should be not more than 5.0m and their height should not be more than 2.1m

2. There should be no other openings within 2.0m of a wall containing a major opening.

3. The aggregate size of openings in a wall not containing a major opening should be not more than 2.4m2.

4. There should not be more than one opening between piers.

5. Unless there is a corner pier the distance from a window or a door to a corner should not be les s than 390 mm.

Isolated column

No

othe

r op

enin

gs in

thi

s zo

ne

2.0m

Wall with major openings

390m

m m

in

390mm min


1.D.40 Wall thicknesses and piers The walls should have a minimum thickness of 90mm. The minimum pier size ( AP x BP) should be 390mm x 190mm or 327mm x 215mm depending on the

olated columns should be 325mm x 325mm minimum (CC x CC ) Walls which do not contain a major opening but exceed 2.5m in length or height should be bonded or tied to piers for their full height at not more than 3m centres as shown in the diagram below Wall without a major opening

m max 3.0m max

size of the masonry units Is

3.0m max 3.0

90mm min BPAP AP

ould be at, 20mm x 3mm in cross section, be in

stainless steel in accordance with clause 1.D.16, be placed in pairs and be spaced at not more than 300mm centre vertically

Wall with a single major opening Walls which contain one or two major openings should in addition have piers as shown in the Diagrams above and opposite. Where ties are used to connect piers to walls they shfl G

BP

AP

Dotted lineindicates rangeof wall positions

G > 2.5mAP

BP

BP

AP

G 2.5m

Wall with two major openings

Dotted line indicatesrange of wall positions

AP

BP

CC

CC


1.D.41 Horizontal lateral restraint at roof level Walls should be tied horizontally at no more than 2m centres to the roof structure at eaves level, base of gables and along roof slopes with straps fixed in accordance with clauses

ass through a

1.D.34 and 1D.35 and where straps cannot pwall they should be adequately secured to the masonry using suitable fixings and isolated columns should also be tied to the roof structure all as shown below. Fixings should be in accordance with the diagram opposite.

1.D.42 Proportions for Masonry Chimneys Where a chimney is not adequately supported by ties or securely restrained in any way, its height if

easured from the high st point of intersection with the roof surface, gutter, etc should not exceed .5W, provided the density of the masonry is greater than 1500 kg/m3 where -

W is the least horizontal dimension of the chimney measured at the same point of intersection; and H is measured to the top of any chimney pot or other flue terminal.

em

4

H H

W W

Level of highest point of

intersection

domestic structure SBSG annex 1.F 2007

Annex 1.E Timber frame walls 1.E.0 Introduction 1.E.1 Wall types 1.E.2 Conditions relating to the Building of which the walls forms part 1.E.3 Maximum floor area 1.E.4 Imposed loads on roofs , floors and ceilings Wall structure 1.E.5 General 1.E.6 Minimum thickness of external walls 1.E.7 Walls providing vertical support to other walls 1.E.8 Timber frame wall sizing 1.E.9 Site data 1.E.10 Building data 1.E.11 Horizontal loads 1.E.12 Wall sheathing 1.E.13 Site data and building data 1.E.14 Altitude/distance category 1.E.15 Length/width ratio 1.E.16 Racking bands 1.E.17 Percentage openings 1.E.18 Masonry cladding arrangements 1.E.19 Panel sheathing and nailing 1.E.20 Vertical loads 1.E.21 Wall stud sizing 1.E.22 Cripple stud sizing 1.E.23 Lintel sizing 1.E.24 Example 1.E.25 Overall stability 1.E.26 Maximum allowable length and height of wall Construction materials and workmanship 1.E.27 General 1.E.28 Wall ties 1.E.29 Masonry cladding 1.E.30 Brick and block construction 1.E.31 Mortar 1.E.32 Lintels for masonry cladding 1.E.33 Timber members 1.E.34 Wall sheathing 1.E.35 Fasteners 1.E.36 Fabrication 1.E.37 Composite action 1.E.38 Wall panel connections 1.E.39 Nailing and fixing schedule Loading on walls 1.E.40 Maximum span of floors 1.E.41 Other loading conditions 1.E.42 End restraint Openings, notching and drilling 1.E.43 General 1.E.44 Framing of openings 1.E.45 Dimensional criteria for openings 1.E.46 Small unframed openings 1.E.47 Notching and drilling 1.E.48 Lateral support by roofs and floors 1.E.49 Differential movement


annex

1.E Walls in certain small buildings – timber frame

1.E.0 Introduction Small buildings of masonry clad platform frame construction can be designed to provide designs taking into account loading conditions , limitations on dimensions , openings and subject to , restraint conditions . This structural guidance for timber frame construction for small buildings is intended to be similar to that for masonry construction restricted to cover a limited range of timber frame wall dimensions, member sizes and loading conditions which commonly apply in Scotland. To comply with the philosophy of the Small Buildings Structural Guidance, the guidance for timber frame construction has been produced for use by those who have expertise in building design and construction but not necessarily in structural engineering design. Where the conditions or parameters fall outside the scope then specialist advice should be sought from chartered engineers with the appropriate skills and experience. This guidance is based on the Platform Frame method of timber frame construction with external masonry cladding being the most common form of timber frame construction in Scotland It is restricted to the member sizes and types and sheathing materials which are commonly used in small buildings in Scotland. It should be noted that the guidance within this Annex only relates to Section 1 Structure. There are other factors such as cavity barriers, breather membranes ,thermal insulation, etc which may be relevant and reference should be made to the appropriate sections in the Technical Handbooks. Timber frame construction outwith the parameters and materials covered in this guidance should be designed in accordance with the guidance in BS 5268 Part 6.1 1996.

This Annex provides guidance for timber frame wall construction for the following building types a. domestic buildings of not more than 2 storeys where loading criteria for individual floors does not

exceed those given in 1.E.4 and total limit of loading does not exceed that given in 1.E.41;

There is guidance in Annex 1.D: Masonry walls which is relevant to this annex with respect to masonry cladding to timber frame walls. 1.E.1 Wall types This Annex deals only with the types of wall extending to full storey height set out below. a. Domestic buildings of not more than 2 storeys

• External walls • Internal load bearing walls • Compartment walls • Separating walls

This Annex should be used in conjunction with Annexe 1.B ; and a. if a timber wall structure is designed in accordance with the guidance in Annex 1.E, all

appropriate design conditions should be satisfied; b. walls should comply with the relevant recommendations of BS 5268: Part 6.1: 1996, except as

regards the conditions given in 1.E.2,1.E.3-4 and 1.E.8-49 c. in formulating the guidance of this Annex, the worst combination of circumstances likely to

arise was taken into account. d. If a recommendation of this Annex is considered too onerous in a particular case then

adequacy by calculation should be shown in respect of the aspect of the wall which is subject to the departure rather than for the entire wall;

e. the guidance given in this Annex is based upon the material strengths of timber , sheathing , plasterboard and masonry being not less than that indicated in 1.E.27-39

f. roof construction should be : • duo or mono pitch trussed rafters with 15-45o pitch and dead weight not more than 1.036

kN/m2 on the slope


• or flat ,raised tie or collared roofs in accordance with guidance in Annex 1.F. g. floor dead load should be not more than 0.5 kN/m2 h. Internal , party and external wall dead loads should be not more than 1.5 kN/m excluding

masonry cladding i. panel heights should be not more than 2.7 m j. timber frame walls act should compositely with the masonry cladding ,sheathing and inner

plasterboard lining all contributing to the racking resistance of the timber frame walls. This guidance does not cover hipped ends to roofs with girder trusses which impose point loads on to the walls or other situations where point loads occur. Wall sheathing which provides the racking resistance to wind loading generally is the limiting factor and this aspect should be checked prior to carrying the remainder of the design. It is unlikely that this guidance could be used with walls with openings more than 30 % of the total wall area or for front gable buildings where there are large percentage openings in the shorter length walls. 1.E.2 Conditions relating to the Building of which the walls forms part This Annex applies only to buildings having proportions within the following limits and as shown on the Diagrams below subject to the limits of 1.E.26 The maximum height of the building measured from the lowest finished ground level adjoining the building to the highest point of any wall or roof must not be greater than:

10 m for duo pitch roofs 5.5 m for mono pitch or flat roofs

• the height of the building H, should not exceed twice the least width of the building W1, the height of the wing H2 should not exceed twice the least width of the wing W2 when the projection P exceeds twice the width W2.

lowest ground level

Maximum height

H not to exceed10m

H

Minimum width

W1

H

W1 not to be lessthan 0.5H

W1

H2

W2W1

P1

1.E.3 Maximum floor area The guidance in this annex applies where - • Floors enclosed by structural walls on all sides do not exceed 70 m2; and • floors without a structural wall on one side do not exceed 36 m2









The i on roofs ceilings should not exceed those given in the table below.

Roof distributed load:

1.50 kN/m for spans up to 6 metres

1.E.4 Imposed loads on roofs , floors and ceilings

mposed loads

Element Load, floors and

ing

1.00 kN/m for spans up to 12 metres 2

2

Floors distributed load: kN/m together with a concentrated load of 1.4 2.00 2

kN

Ceilings distributed load: 0.25 kN/m together with concentrated load: 0.9 kN 2

The guidance for snow loading in 1.F.6 applies only to a free standing flat roofed structure with no parapet and with the roof on one level only, provided that there are no other buildings within 1.5m of its perimeter.


Wall structure 1.E.5 General Wall structure should be determined according to this Annex provided the following conditions are met- a. relating to the building of which the wall forms a part (1.E.2); and b. relating to the wall 1.E.3-49

Conditions – building d. limitations on size and proportions of building and parts of building ( 1.E.2, ) e. max allowable floor areas ( 1.E.3) f. max imposed and wind loads ( 1.E.12.) Conditions – wall i. max allowable length and height of wall ( 1.E.26) j. construction materials and workmanship ( 1.E.27-39) k. loading on walls ( 1.E.40 and 1.E.41) l. end restraints ( 1.E.42) m. openings, notching and drilling (1.E.43-47) n. lateral support by floors and roofs (1.E.48) o. Differential movement (1.E.49)

Are building conditions satisfied ?

Use Annex 1.E for timber frame walls

Conditions relating to building of which wall is part

Outside Annex 1.E scope

Outside Annex 1.E scope

Yes

Are wall conditions satisfied?

No

No

Yes

1.E.6 Minimum thicknesses of external cavity walls Masonry clad timber frame walls should comprise masonry cladding for at least 100 mm thick ,50 mm nominal cavity width 9mm nominal sheathing thickness and timber studs at least 89 mm depth and plasterboard inner wall lining . Wall ties should be securely nailed to the vertical studs and not to the sheathing alone generally at the following spacings a. Brickwork cladding: horizontal spacing of 600mm and a vertical spacing of 375mm b. Blockwork cladding : horizontal spacing of 400 or 600mm and a vertical spacing of 450mm, c. Wall ties should also be provided, spaced not more than 300mm apart vertically, within a distance of 225 mm from the vertical edges of all openings, movement joints and roof verges. d. In exposed wind locations, the tie density would require to be increased in accordance with BS 5268 -6.1:1996. e. For specification of cavity wall ties refer to 1.E.28

1.E. 7 Walls providing vertical support to other walls Irrespective of the materials used in the construction, a wall should not be less in thickness than any part of the wall to which it gives vertical support.


1.E.8 Timber frame wall sizing The following procedure which should be followed to determine the member sizing etc for masonry clad timber frame wall construction which should be adequate for a particular location depending on the building dimensions and the site exposure conditions is based on BS 5268-6.1 The procedure is summarised in the flow chart below and explained in detail thereafter together with a worked example in 1.E.24. Design Procedure Flow Chart

Assess Building Data( 1.E.10)

Length / Width ratio (1.E.11

Assess Site Data( 1.E.12)

Wall Sheathing Requirements(1.E.13-18)

Horizontal(Wind) Loads (1.E.19)

Vertical(Snow ) Loads ( 1.E20)

Wall Stud Requirements ( 1.E.21)

Cripple Stud Requirements(1.E.22)

Lintel requirements (1.E.23)


1.E.9 Wall sheathing The horizontal loads arising from wind action are resisted and transferred to the base of the walls by the racking resistance of the racking ( or wind) wall panels . Walls should only be considered to be Racking Walls and hence able to provide resistance to wind action if they are specifically designed in accordance with the following racking procedure and have at least one layer of OSB3 or plywood sheathing secured to the timber studs. The Flow Chart below and subsequent clauses provide guidance on how to provide adequate racking resistance by means of racking or wind walls comprising wall sheathing and nailing arrangements .. Racking Procedure Flow Chart

Building and Site Data including assessing β = B/A (1.E.10-12)

Read off Altitude-Distance Category from Table to 1.E.13

Assess the percentage openings in each wall of Building(1.E.15)

Assess the Masonry Cladding Arrangement from Table to 1.E.16

Select Panel Sheathing and Nailing requirements (1.E.17)

Read Racking Band from Tables to 1.E.14

Use of internal racking walls, if appropriate (1.E.17)


1.E.10 Building Data stage 1 Assess the following dimensions for the building : • Overall outside plan width , A • Overall outside plan length, B • Height from ground level to eaves ,H • Overall Building Height from ground

level to ridge • Number of storeys • Roof shape :- duopitch , monopitch or

flat • Spans of roof and floors Key A : Building Width (smaller dimension of

the building cross-section (plan) B : Building Length (larger dimension of the

building cross-section (plan) β: Length/ Width Ratio of the building

plan β = B/A.

Building dimensions

H

Duo pitch roof Mono pitch roof

AR

BR

A

B

Flat roof Plan

1.E.11 Length/width ratio stage 2 Determine the length/ width ratio, β in accordance with the diagram above Note that β should always be rounded up from the derived value to the nearest 0.5 and will be not less than 1.0 in any case.


1.E.12 Site Data stage 3 a. Determine the site location of the building under consideration b. Assess the distance of the site to the coast within the following ranges

• Not more than 10 km • not more than 100 km • greater than 100 km Where a site is nearer than 1 km to an inland area of water which extends more than 1 km in the wind direction , the distance to the coast should be taken as from the edge of the water.

c. Assess the altitude of the site above ordinance datum within the following ranges • 0 m • not more than 50 m • not more than 100m • not more than 150m • not more than 200m • not more than 300m • not more than 400 m

d. Determine the snow zone as A or B from the snow map below Determine the wind speed from the wind speed map below Snow Zone Map Wind Speed Map ( m/s)

Inverness

Zone AB


1.E.13 Altitude/distance category stage 4 the Site Altitude and Distance to the coast,

AD1-AD6 :Altitude / Distance to the coast Category < : less than

Usingread the Altitude-Distance category (AD1-AD6) fromthe table oppositeKey

< : not more than

le Alti istan tegnce t coa )

Tab tude/d ce ca ory Dista o the st(kmAltitude <10 <100 >100

0m AD1 AD1 AD1 < 50m AD1 AD1 AD1 < 100m AD2 AD2 AD2 << 200m

150m AD3 AD3 AD3 AD4 AD3 AD3

< 300m AD5 AD5 AD4 < 400m AD6 AD6 AD5

1.E.14 Racking Bands stage 5 The Racking Band is the wind force on to an external wall panel in a parallel direction to that panel as

can be read from the relevant table below using the

h roofed buildings for heights of 5.5 and 10 metres

roofed buildings for heights of 5.5 metres height for ind speeds of 30, 27, 25 and 23 metres / sec able 9-12 provide racking bands for duo pitch roofed buildings for heights of 5.5 metres height for

es / sec

shown in the diagram in clause 1.E.10 andfollowing information derived above • Building height H, and roof type from clause 1.E.10 • Length/width ratio, β from clause 1.E.11 • Wind speed from clause 1.E.12 • Altitude / distance, AD, category from clause 1.E.13 Tables 1-4 provide racking bands for duo pitcheight for wind speeds of 30, 27, 25 and 23 metres / sec Table 5-8 provide racking bands for duo pitchwTwind speeds of 30, 27, 25 and 23 metr

Ra ing sTa e 1 ind

m h H t

ck Band for Duopitch roofs bl W speed = 30m/s

5.5 Heig t 10m eigh β Side tud is e e (A ud is e e (AD) Alti e/D tanc Cat gory D) Altit e/D tanc Cat gory AD1 A A AD4 AD5 A AD2 A A AD5 AD6 AD7 D2 D3 AD6 AD7 D1 D3 D4

1 A R3 R3 R3 R4 R4 R5 R5 R5 R6 R8 R9 R11 - - B R3 R3 R3 R3 R4 R4 R5 R7 R8 R9 R11 R11 - -

1.5 R11 R11 A R6 R6 R7 R8 R9 - - - - - - - B R2 R2 R2 R R3 R3 R3 3 - - - - - - -

2 A R8 R9 R R R 11 11 11 - - - - - - - - - B R1 R1 R R R 2 2 2 - - - - - - - - -

2 R .5 A R11 R11 11 - - - - - - - - - - - B R1 R R 1 1 - - - - - - - - - - -

3 A R11 R11 - - - - - - - - - - - - B R R -1 1 - - - - - - - - - - -

3 R -.5 A 11 - - - - - - - - - - - - B R1 - - - - - - - - - - - - -

4 A - - - - - - - - - - - - - - B - - - - - - - - - - - - - -


Ra ng s focki Band r Duopitch roofs Ta 2

. ig 0 eble Wind speed = 27m/s 5 5 He ht 1 m H ight

Al e ta C go A Al e ta go titud /Dis nce ate ry ( D) titud /Dis nce Cate ry (AD)β Side AD1 AD2 AD3 AD4 AD5 AD6 AD7 AD1 AD2 AD3 AD4 AD5 AD6 AD7 1 A R2 R2 R3 R3 R3 R4 R4 R4 R5 R6 7 R R9 R11 - B R2 R2 R2 R3 R3 R3 R4 R6 8 R6 R7 R R9 R11 -

1.5 A R5 R5 R6 R6 R7 R8 R9 R11 1 R1 - - - - - B R1 R2 R2 R2 R2 R2 R3 R4 R5 - - - - -

2 A R7 R7 R8 R9 R11 1 1 R1 R1 - - - - - - - B R1 R1 R1 R1 R2 R2 R2 - - - - - - -

2.5 A R8 R9 R11 R11 R11 - - - - - - - - - B R1 R1 R1 R1 R1 - - - - - - - - -

3 A R9 R11 1 R11 R1 - - - - - - - - - - B R1 R1 R1 R1 - - - - - - - - - -

3.5 1 A R11 R11 R1 - - - - - - - - - - - B R1 R1 R1 - - - - - - - - - - -

4 A R11 R11 - - - - - - - - - - - - B R1 R1 - - - - - - - - - - - -

Racki ang B nds for Duopitch roofs Table 3 Wind speed = 25m/s

He t m H ght 5.5 igh 10 eiAltitud is e go A u is e g Ae/D tanc Cate ry ( D) Altit de/D tanc Cate ory ( D)

β Side AD

1 AD2

AD3

AD4

AD5

AD6

AD7

AD1

AD2

AD3

AD4

AD5

AD6

AD7

1 A R2 R2 R2 R2 R3 R3 R3 R4 R4 R5 R6 11 R7 R9 R B R2 R2 R2 R2 R3 R3 R3 R5 R5 R6 R7 R7 R8 R9

1 1 1 1 .5 A R4 R4 R5 R5 R6 R7 R7 R1 R1 R1 - - - - B R1 R1 R1 R2 R2 R2 R2 R3 R4 R4 - - - -

2 A R5 R6 R7 R7 R8 R9 R11 - - - - - - - B R1 R1 R1 R1 R1 R1 R2 - - - - - - -

2.5 1A R7 R7 R8 R9 R11 R11 R1 - - - - - - - B R1 R1 R1 R1 R1 R1 R1 - - - - - - -

3 A R8 R8 R9 R11 R11 R11 - - - - - - - - B R1 R1 R1 R1 R1 R1 - - - - - - - -

3.5 1A R8 R9 R11 R11 R1 - - - - - - - - - B 1 1 1 1 1 R R R R R - - - - - - - - -

4 A R9 R11 R11 R11 - - - - - - - - - - B R1 R1 R1 R1 - - - - - - - - - -


R ki Baac ng nds for Duopitch roofs Table 4 Wind speed = 23m/s

5.5 H t Heigh 10m eight Altitu Dis e eg A itu i ce g (de/ tanc Cat ory ( D) Alt de/D stan Cate ory AD) β Side AD1 AD2 AD3 AD4 AD5 AD6 AD7 AD1 AD2 AD3 AD4 AD5 AD6 AD7

1 A R1 R2 R2 R2 R2 R2 R3 R3 R3 R4 R5 R6 R7 R9 B R1 R1 R2 R2 R2 R2 R2 R4 R4 R5 5 R R6 R7 R8

1.5 11 1 A R3 R3 R4 R4 R5 R5 R6 R8 R9 R9 R R1 - - B R1 R1 R1 R1 R1 R2 R2 R3 4 R3 R3 R R4 - -

2 A R4 R5 R5 R6 R7 R7 R8 R11 1 R1 - - - - - B R1 R1 R1 R1 R1 R1 R1 R2 R2 - - - - -

2.5 A R5 R6 R6 R7 R8 R9 R11 - - - - - - - B R1 R1 R1 R1 R1 R1 R1 - - - - - - -

3 A R6 R7 R7 R8 R9 R11 R11 - - - - - - - B R1 R1 R1 R1 R1 R1 R1 - - - - - - -

3.5 1 -A R7 R7 R8 R9 R11 R11 R1 - - - - - - B R1 R1 R1 R1 R1 R1 R1 - - - - - - -

4 A R7 R8 R9 R11 R11 R11 - - - - - - - - B R1 R1 R1 R1 R1 R1 - - - - - - - -

R king Baac nds for Monopitch roofs T 3 e eable 5 Wind speed = 0m/s Tabl 6 Wind spe d = 27m/s Height He 5.5 5.5 ight

Altitu Dis e eg A itu i ce g (Ade/ tanc Cat ory ( D) Alt de/D stan Cate ory D) β Side AD1 AD2 AD3 AD4 5 6 7 4 6AD AD AD AD1 AD2 AD3 AD AD5 AD AD7 1 A R5 R6 R6 R7 8 R8 R R9 R4 R5 R5 R6 R6 R7 R8 B R3 3 4 3 R3 R R4 R4 R R5 R2 R2 R3 R R3 R3 R4

1.5 1 1 11 1 A R1 R1 R - - - - R8 R9 R9 R R1 - - B R2 2 1 2 R2 R - - - - R R2 R2 R R2 - -

2 A - - - - - - - R11 1 R1 - - - - - B - - - - - - - R1 R1 - - - - -

2.5 A - - - - - - - - - - - - - - B - - - - - - - - - - - - - -

R ing Baack nds for Monopitch roofs Table 7 Wind speed = 25m/s Table 8 Wind speed = 23m/s

e5.5 Height 5.5 H ight Altitu Dis e eg A itu i ce g (de/ tanc Cat ory ( D) Alt de/D stan Cate ory AD β=

(B / Side A) AD1 AD2 AD3 AD4 AD5 AD6 AD7 AD1 AD2 AD3 AD4 AD5 AD6 7 AD

1 A R3 R4 R4 R5 R5 R6 R6 R3 R3 R3 R4 R4 R5 R5 B R2 R2 R2 R2 R3 3 R R3 R1 R1 R2 R2 R2 R2 R3

1.5 - 11 1 A R7 R7 R8 R9 R1 R R1 R5 R6 R6 R7 R8 R9 R B R1 R1 R1 2 R2 R2 R R2 R1 R1 R1 R1 R1 R2 R2

2 A R9 R11 11 1 1 R R1 - - - R7 R8 R9 R R1 R11 - B R1 R1 1 R R1 - - - R1 R1 R1 R1 R1 R1 -

2 1 1 .5 A R11 R1 - - - - - R9 R9 R R1 - - - B R1 R1 - - - - - R1 R1 R1 R1 - - -

3 A R11 - 1 - - - - - - R11 R11 R1 - - - - B R1 - - - - - - R1 R1 R1 - - - -

3 - - R 1 .5 A - - - - - 11 R1 - - - - - B - - - - - - - R1 R1 - - - - -

4 A - - - - - - - R11 - - - - - - B - - - - - - - R1 - - - - - -


Rack g Bain nds for Flat roofs

Table 9 Wind speed = 30m/s Table 10 Wind speed = 27m/s Height H t 5.5 5.5 eigh

tu is e g (A itu i ce eg (AAlti de/D tanc Cate ory D) Alt de/D stan Cat ory D) β Side 6 7 AD1 AD2 AD3 AD4 AD5 AD AD AD1 AD2 AD3 AD4 AD5 AD6 AD7 1 A R4 R5 R5 R6 R6 R7 R7 R4 R4 R4 R5 R5 R5 R6 B R4 R5 R5 6 R6 R6 R7 R7 R4 R4 R4 R5 R5 R5 R

1 - 1 1 - 11 .5 A R9 R9 R1 R1 R1 - - R7 R7 R8 R9 R9 R1 R B R3 3 4 R3 R4 R4 R4 - - R2 R3 R3 R R4 R4 R

2 A R11 1 1 11 R1 - - - - - R9 R1- R1 R - - - B R2 R2 - - - - - R2 R2 R2 R2 - - -

2.5 A - - - - - - - R11 R11 - - - - - B - - R1 - - - - - R1 - - - - -

R kac ing Bands for Flat roofs e 2 i Table 11 Wind sp ed = 5m/s Table 12 W nd speed = 23m/s

5.5 H t H t eigh 5.5 eighAltitu is e g (A itu i ce eg (Ade/D tanc Cate ory D) Alt de/D stan Cat ory D) β S e id AD1 AD2 AD3 AD4 AD5 AD6 AD7 AD1 AD2 AD3 AD4 AD5 AD6 AD7

1 A R3 R3 R3 R4 R4 R5 R5 R3 R3 R3 R4 R4 R5 R5 B R3 R3 R3 R4 R4 R5 R5 5 R3 R3 R3 R4 R4 R5 R

1 9 .5 A R6 R6 R7 R7 R8 R9 R9 R6 R6 R7 R7 R8 R9 R B R2 R2 R2 R3 R3 4 R3 R4 R2 R2 R2 R3 R3 R3 R

2 A R8 R9 R9 R1- R11 1 1 1 R1 - R8 R9 R9 R1- R1 R1 - B R1 R1 R2 2 R2 R2 R2 - R1 R1 R2 R R2 R2 -

2 1 1 1 11 .5 A R9 R1- R1 R1 - - - R9 R1- R1 R - - - B R1 R1 1 R1 R1 - - - R1 R1 R1 R - - -

3 A R11 1 1 R1 - - - - - R11 R1 - - - - - B R1 1 R1 - - - - - R R1 - - - - -

3.5 1 11 A R1 - - - - - - R - - - - - - B R1 - - - - - - R1 - - - - - -

4 A - - - - - - - - - - - - - - B - - - - - - - - - - - - - -

a. ,

b. gs) A = Sum (( W x H ) + (W x H ) + ….(W x H ) )

c. Effesub

encloses both openings.

• Where an opening is less than 300mm from the corner of a building and the depth of opening is greater than half the panel height, and then the length of that part of the wall, up to and

ed w en determining the total length of wall.

1.E.15 Percentage openings in racking walls stage 6 Assess the Effective External Racking Wall Area, AEX, of the ground floor for each wall as LengthB or Width, A x Height from ground level to first floor level .: AEX = A x H and B x H Assess the Total Opening Area, AO , of the ground floor for each of the walls ( sum of lengths times widths of all openin O 1 1 2 2 N NAssess the Allowable Percentage Wall Openings in each wall as percentage Total Opening Area /

ctive External Racking Wall Area for each external face of the building : %Op = AO /AEX % ject to the following:

• Where two framed openings are separated by less than 300mm and the heights of both openings are greater than half the panel height, the area of opening should be taken as the rectangle that

• Where there are limited areas of alternative cladding panels such as timber cladding above doors or windows (not exceeding 0.5 m2 these areas should be should be added to the areas of openings.

including the opening, should be disregard h


L = Length of wall

P1 P2 W2 P3 W3W1 P4

H1H

A1 A2 A3

H2

H1

H2

Effective External Racking Wall Area, AEX = L x H

1) + (W3 x H3)

%Op = ( AO / AEX ) x 100

f P1 <300mm and H1 > H/2 ,then L becomes ( L – P1 )

mm then ( A1 + A2) = (W1 +P2 + W2 ) x H1

f the area above an opening is timber cladding

Total Opening Area , AO = (W1 x H1) + (W2 x H Percentage Wall Opening, I If P2 < 300 Ithen A2 = W2 x (H1 + H2 ) and A3 = W3 x (H3 + H4) 1. stage 7 Assess the Masonry Cladding arrangement Type from the Table below

gem

E.16 Masonry Cladding Arrangement

Masonry cladding arran

Type 1 ent type

Type 2 Type 3 For masonry walls with buttresses or returns not less than 550mm length and not more than 9m centre to centre.

e

r sses or

returns less than 550mm length and wall length not more than 4.5m

lls without buttresses or returns or with buttresses or returns of less than 550mm length.

For masonry walls with buttresses or returns at onend of wall not less than 550mm length with the otheend without buttre

For masonry wa

.17 Panel Sheathing and Nailing stage 8 The Wall Sheathing in combination with the nailing of the sh

1.Ea. eathing to the wall studs provides the

d ) force in the plane of that panel as shown in the sheathing and nailing can be read from the relevant

derived above •

a. s

l sheathing for Wall Type 2 at 1 and 2 Storey buildings. e 3 for 1 and 2 Storey buildings.

b. s for the Racking Bands and Percentage Wall

•

resistance of the wall to the racking ( windiagram in clause 1.E.10 and combinations ofcharts below using the following information Racking Band , R , from clause 1.E.14 • Percentage Openings from clause 1.E.15 • Masonry Wall Type from clause 1.E.16 Select the appropriate chart below based on the Wall Type and number of storey• Chart 1 provides wall sheathing for Wall Type 1 for 1 and 2 Storey buildings. • Chart 2 provides wal• Chart 3 provides wall sheathing for Wall TypRead off the allowable walling configurationOpenings for each wall • Double sheathed with 100mm nail centres Double sheathed with 150mm nail centres


••

c. ld. I

• the parameters particularly the Percentage Wall Openings; • or consider introducing an internal racking wall ( refer to clause 1.E.18); • or specialist advice should be sought from chartered engineers with the appropriate skills

Charts 1-3 Wall details and allowable percentage of openings for given racking banding

Single sheathed with 100mm nail centres Single sheathed with 150mm nail centres

Se ect the most appropriate Walling Configurations Option f the required percentage openings/racking bands are outwith the charts

either reconsider

and experience.

0

10

20

30

40

50

60

70

Racking band

Allowable percentage openingin panel %.

Double sheathed w ith 100mm nail centres

Double sheathed w ith 150mm nail centres

Single sheathed w ith 100mm nail centres

Single sheathed w ith 150mm nail centres

R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11

Perimeter nail spacing

Chart 1 Wall Type 1 at 1 & 2 Storey: Wall details and allowable percentage of openings for given racking banding


0

10

20

30

40

50

60

70

Racking band

Allo

wabl

e pe

rcen

tage

ope

ning

in p

anel

%.

Double sheathed with 100mm nail centres


Single sheathed with 100mm nail centres



R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11

Chart 2 Wall Type 2 at 1 & 2 Storey: Wall details and allowable percentage of openings for given racking banding

0

10

20

30

40

50

60

70

Racking band

Allo

wabl

e pe

rcen

tage

ope

ning

in p

anel

%.






R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11

Chart 3 Wall Type 3 at 1 & 2 Storey: Wall details and allowable percentage of openings

for given racking banding


1.E.18 Use of internal walls for additional racking resistance stage 9 Internal walls can be used to provide additional racking resistance provided the following apply to such walls a. satisfactory fixity to the foundations , floor or roof diaphragms as appropriate b. no segments of wall being used is less than 600 mm in length c. the assessed internal racking length is the shortest length of all storeys in that direction ( eg for a

2 storey building, if level one has 2 internal racking walls of say C1 and C3 and level two has only C2, then C is the smaller of (C1+C3) and C2, for that building).

Key A is the smaller dimension of the building plan B is the larger dimension of the building plan C is the sum of the lengths of the internal racking

resisting walls (C = C1 + C2 + C3 + ….), β can be considered as B/(A+0.5×C) but not less than 1.0

in any case. It is recommended that this value is always rounded up when calculated (i.e. if A = 3, B = 5 and C = 1.2 then β= 5/(3+0.5×1.2) = 1.38 thus adopt β= 1.5 but if A = 4, B = 5 and C = 2.5 then β= 5/(4+0.5×2.5) = 0.92 thus adopt β=1.0)

AR

BR

C1

C2

C3

A

B

Plan where there are internal racking walls

Internal racking walls parallel to the length of the building (i.e. B) should be ignored in the calculation of β. However they can be used to enhance racking resistance in that direction to allow for an increased percentage of openings as follows: The Effective internal racking wall area, AIN, should be split equally between each of the external racking wall areas, AEX, which are parallel to that internal wall allowing the allowable percentage of opening calculated from clause 1.E.15 may be increased using the following equation:

AOP = (AEX + (AIN / 2)) × %Op

Where: AOP Area of allowable opening AEX Effective external racking wall area AIN Effective internal racking wall area %Op Allowable percentage of openings per storey from charts 1-3 .


1.E.19 Horizontal loads stage 10 The Horizontal ( wind ) loads are derived from the wind speed map and can be read from the table below using the following information derived from above • Overall Building height, H from clause 1.E.10 • Distance to the coast , Site Altitude and Wind Speed from clause 1.E. 12

Table of Horizontal Loads Site altitude (a)

0m a < 50m 50m< a < 100m 100m< a < 150m Distance to the coast(km)

Building height

Wind speed (m/s) <10 <100 >100 <10 <100 >100 <10 <100 >100 <10 <100 >100

<5.5m 23 H1 H1 H1 H1 H1 H1 H1 H1 H1 H1 H1 H1 25 H1 H1 H1 H1 H1 H1 H1 H1 H1 H1 H1 H1 27 H1 H1 H1 H1 H1 H1 H2 H1 H1 H2 H2 H1 30 H2 H1 H1 H2 H2 H1 H2 H2 H2 H3 H2 H2 <10m 23 H1 H1 H1 H1 H1 H1 H1 H1 H1 H1 H1 H1 25 H1 H1 H1 H1 H1 H1 H2 H1 H1 H2 H2 H1 27 H2 H1 H1 H2 H1 H1 H2 H2 H2 H2 H2 H2 30 H2 H2 H2 H3 H2 H2 H3 H3 H2 H4 H3 H3

Site altitude (a) 150m< a < 200m 200m< a < 300m 300m< a < 400m

Distance to the coast(km) Building height

Wind speed (m/s) <10 <100 >100 <10 <100 >100 <10 <100 >100

<5.5m 23 H1 H1 H1 H2 H2 H1 H2 H2 H1 25 H2 H2 H1 H2 H2 H1 H3 H3 H2 27 H2 H2 H1 H3 H3 H2 H4 H3 H3 30 H3 H3 H2 H4 H4 H3 H5 H4 H3 <10m 23 H2 H2 H1 H2 H2 H2 H3 H3 H2 25 H3 H3 H2 H3 H3 H2 H3 H3 H3 27 H3 H3 H2 H4 H3 H3 H5 H4 H4 30 H4 H4 H3 H5 H5 H4 H6 H6 H5

1.E.20 Vertical Loads stage 11 The Vertical loads are derived from the snow zone map in clause 1.E.12 using the following information derived from above • Roof and Floor Spans and the Number of Storeys from clause 1.E.10 • Snow Zone and Site Altitude from clause 1.E.12 a. The Imposed Loads (Snow ) in kN/m2 is read from the table below Imposed roof loads ( kN/m2 ) Zone Altitudes below 100m Altitudes between 100m

and 200 m Altitudes between 200m and 260 m

A 0.75 1.00 Refer to BS 6399: Part 3 B 1.00 1.50 1.5


b. Read the Vertical ( Snow) Load Category (V1-V18) from the table below Table of vertical loads at heads of panels

Imposed loads

1.0 kN/m2 1.5 kN/m20.75 kN/m2Roof or

floor span (m)

Roof or floor

Roof + Roof or floor

Roof + Roof or floor

Roof + 1 storey 1 storey 1 storey

1 V1 V3 V1 V3 V2 V3 2 V4 V7 V4 V7 V5 V7 3 V6 V10 V6 V10 V7 V11 4 V8 V12 V8 V12 V9 V13 5 V10 V13 V10 V14 V11 V14 6 V10 V14 V11 V15 V11 V15 7 V11 V16 V11 V16 V12 V17

7.5 V11 V17 V13 V17 V13 V18 1.E.21 Wall Stud Sizing stage 12 The wall studs carry the horizontal and vertical loads imposed on the timber frame panels and the sizes of studs can be selected using the tables below using the following information derived from above • Horizontal (Wind) Load Category (H1-5) from clause 1.E.19 • Vertical(Snow) Load Category (V1-V22) from clause 1.E.20 The most appropriate wall stud sizes , spacing and timber grade for the wall panels should be selected from the tables below Note that timber of strength class C16 is generally used for wall studs Tables of Minimum wall stud sizes in softwood for all snow zones Table 1 Horizontal load category H1 Timber of strength class grade C16 Timber of strength class grade C24 Vertical load category

Timber Size mm x mm

Spacing (mm)

Vertical load category

Timber Size Spacing (mm)mm x mm

V1-V11 38 x 89 400 V1-V16 38 x 89 400 V1-V7 600 V1-V10 600 V1-V20 38x 114 400 V1-V22 38x 114 400 V1-V14 600 V1-V17 600 V1-V22 38 x 140 400 V1-V22 38 x 140 400 V1-V19 600 V1-V19 600

Table 2 Horizontal load category H2 Timber of strength class grade C16 Timber of strength class grade C24 Vertical load category

Timber Size mm x mm

Spacing (mm)


Timber Size mm x mm

Spacing (mm)




Timber Size mm x mm

Spacing (mm)


Timber Size mm x mm

Spacing (mm)



Timber Size mm x mm

Spacing (mm)


Timber Size mm x mm

Spacing (mm)

V1-V8 38 x 89 400 V1-V12 38 x 89 400 V1 600 V1-V6 600 V1-V16 38x 114 400 V1-V22 38x 114 400 V1-V10 600 V1-V13 600 V1-V21 38 x 140 400 V1-V22 38 x 140 400 V1-V16 600 V1-V19 600


Timber Size mm x mm

Spacing (mm)


Timber Size mm x mm

Spacing (mm)

V1-V7 38 x 89 400 V1-V12 38 x 89 400 None 600 V1-V5 600 V1-V16 38x 114 400 V1-V21 38x 114 400 V1-V19 600 V1-V12 600 V1-V21 38 x 140 400 V1-V22 38 x 140 400 V1-V15 600 V1-V19 600

1.E.22 Cripple Stud Sizing stage 13 Cripple studs are connected to studs either side of an opening within a panel to provide support to a lintel above the openings as shown opposite. The sizes and numbers of cripple studs can be selected using the table below using the following information derived from above

• Lintel Span from clause 1.E.10 • Vertical Load Category (V1-V22) from

clause 1.E.20 a. Select the most appropriate cripple stud

sizes, numbers of sections and timber grade required for the lintel spans from the tables below

cripplestuds

reproduced by permission of TRADA

b. The number of cripple studs required from the table is the number of studs in addition to the wall studs on each side of the opening

c. All cripple studs should be of the same strength class and size d. Timber of strength class C16 is generally used for posts/cripple studs e. Where more than 3 sections are required to make up a cripple stud specialist advice should be

obtained.


Minimum Cripple stud sizes and numbers in softwood Table 1 Timber of Strength class Grade C16

Lintel span (mm) Vertical load category 1240 1800 2475 Stud size 38x89 38x114 38x140 38x89 38x114 38x140 38x89 38x114 38x140

V1 1 1 1 1 1 1 1 1 1 V2 1 1 1 1 1 1 1 1 1 V3 1 1 1 1 1 1 2 1 1 V4 1 1 1 1 1 1 2 1 1 V5 1 1 1 2 1 1 2 1 1 V6 2 1 1 2 1 1 2 1 1 V7 2 1 1 2 1 1 2 1 1 V8 2 1 1 2 1 1 2 1 1 V9 2 1 1 2 1 1 2 2 1

V10 2 1 1 2 1 1 3 2 1 V11 2 1 1 3 2 1 3 2 1 V12 2 1 1 3 2 1 - 2 2 V13 2 1 1 3 2 1 -- 2 2 V14 3 2 1 -- 2 2 -- 3 2 V15 3 2 1 -- 2 2 -- 3 2 V16 3 2 1 -- 2 2 -- 3 2 V17 3 2 1 -- 3 2 -- 3 2 V18 3 2 1 -- 3 2 -- 3 2

Table 2 Timber of Strength class Grade C24

Lintel span (mm) Vertical load category 1240 1800 2475 Stud size 38x89 38x114 38x140 38x89 38x114 38x140 38x89 38x114 38x140

V1 1 1 1 1 1 1 1 1 1 V2 1 1 `1 1 1 1 1 1 1 V3 1 1 1 1 1 1 1 1 1 V4 1 1 1 1 1 1 2 1 1 V5 1 1 1 1 1 1 2 1 1 V6 1 1 1 2 1 1 2 1 1 V7 2 1 1 2 1 1 2 1 1 V8 2 1 1 2 1 1 2 1 1 V9 2 1 1 2 1 1 2 1 1

V10 2 1 1 2 1 1 3 1 1 V11 2 1 1 3 1 1 3 2 1 V12 2 1 1 3 2 1 -- 2 2 V13 2 1 1 3 2 1 -- 2 2 V14 3 2 1 -- 2 2 -- 3 2 V15 3 2 1 -- 2 2 -- 3 2 V16 3 1 1 3 2 2 -- 3 2 V17 3 2 1 -- 3 2 -- 3 2 V18 3 2 1 -- 3 2 -- 3 2


1.E.23 Lintel Sizing Lintels provide support to openings and are supported by cripple studs at either end as shown on the diagram to clause 1.E.22 The sizes and numbers of sections for lintels can be selected using the table below using the following information derived from above • Lintel Span from clause 1.E.10 • Vertical Load Category (V1-V22) from clause 1.E.20 a. Select the most appropriate lintel sizes, numbers of sections and timber grade required for the

lintel spans from the table below • The lintel span is the clear distance between support points of the cripple studs • Timber of strength class C24 is generally used for lintels • All lintels should be of the same strength class and size. • 2x38x190 means 2 No lintels 38 mm wide by 190 mm deep are required to satisfy the

loading condition • Where more than 3 sections are required to make up a lintel, or steel inserts (e.g. flitch

beams) are required then specialist advice should be obtained. Minimum lintel sizes and numbers in softwood Table 1 Timber of Strength class Grade C16

Lintel span (mm) 1240 1800 2475 Lintel sections and numbers

Vert load

38x1

40

38x1

90

44x1

40

44x1

90

44x2

200

44x2

40

38x1

40

38x1

90

44x1

40

44x1

90

44x2

200

44x2

40

38x1

40

38x1

90

44x1

40

44x1

90

44x2

200

44x2

40

V1 2 2 2 V2 2 2 2 V3 2 2 2 V4 2 2 2 V5 2 2 3 V6 2 2 3 V7 2 2 3 V8 2 2 3 V9 2 3 3

V10 2 3 -- V11 2 3 -- V12 2 3 -- V13 2 3 -- V14 3 -- -- V15 3 -- -- V16 3 -- -- V17 3 -- -- V18


Minimum lintel sizes and numbers in softwood Table 2 Timber of Strength class Grade C24

Lintel span (mm) 1240 1800 2475 Lintel sections and numbers

Vertical load category 38

x140

38x1

90

44x1

40

44x1

90

44x2

200

44x2

40

38x1

40

38x1

90

44x1

40

44x1

90

44x2

200

44x2

40

38x1

40

38x1

90

44x1

40

44x1

90

44x2

200

44x2

40

V1 2 2 2 V2 2 2 2 V3 2 2 2 V4 2 2 2 V5 2 2 2 V6 2 2 2 V7 2 2 2 V8 2 2 2 V9 2 2 3

V10 2 2 2 V11 2 2 3 V12 2 2 3 V13 2 3 -- V14 3 3 -- V15 3 3 -- V16 3 -- -- V17 3 -- -- V18 3 -- --


1.E.24 Example

Site Data Distance from sea km 15 Altitude ,a m 150 Snow zone A Windspeed m/s 23.5 Building Data Width, A m 7.5 Length, B m 7.6 Height to Eaves m 5.5 Storeys No 2 Building Height, H m 7.5 Roof Shape Duo Panel Height, Hp m 2.4

7.5m

7.5m

5.5m

2.4m

2.4m

B = 7.6m

A=

7.5m

D =

2.7

m1 D =

1.9

m3

D =

1.4

m2

C = 2.5m2C = 3.3m1

C = 2.5m3

B = 7.6m

A=

7.5m

D =

4.1

m4 D =

4.1

m5

C = 2.4m4 C = 2.4m5

C = 2.4m6

Racking Wall Type: 1 Number of storeys: 2 From Table to clause 1.E.13, Altitude-Distance Category = AD3 For Ground Floor:

Internal racking wall, parallel to building width, C = C1 + C2 + C3 = 8.3m Internal racking wall, parallel to building length, D = D1 + D2 + D3 = 6.0m

For First Floor: Internal racking wall, parallel to building width, C = C4 + C5 + C6 = 7.2m Internal racking wall, parallel to building length, D = D4 + D5 + = 8.2m

Adopt lesser values giving : C = 7.2m. D = 6.0m Length/width ratio β = B/ (A + 0.5 ×C) = 7.6/ (7.5 + 3.6) = 0.68. < 1.0 . Therefore adopt β = 1.0

From Table 4 for β = 1.0 ,AD3 category and wind speed of 23 m/s , Racking bands are : For Side A = R4 and for Side B = R5) From the above parameters the initial wall options are as shown in the table below (before allowing for the effect of internal racking walls) Side

Racking Band

Wall Options Allowable % opening/ level per side

Side A R4 From Chart 1 to clause 1.E.17: 1. Single sheathed with 100mm nail centres 2. Single sheathed with 150mm nail centres

19 14

Side B R5 3. Single sheathed with 100mm nail centres 4. Single sheathed with 150mm nail centres

15 10

In accordance with clause 1.E.18 ,% openings in the external walls may be increased:


Width Walls: Effective area of external racking wall, AEX = 7.5m × 2.4m = 18m2

Effective area of internal racking walls, AIN = 7.2m × 2.4m = 17.28m2

Area of allowable opening per level, AOP = (AEX + (AIN / 2)) × %Op

For example consider Side A, Option 1: single sheathed with 100mm nail centres: AOP = (18+ (17.28/2)) × 19% AOP = 5.1m2

Therefore %Op = (5.1 / 18) × 100 = 28%

Length Walls:

Effective area of external racking wall, AEX = 7.6m x 2.4m = 18.24m2

Effective area of internal racking walls, AIN = 6m x 2.4m = 14.4m2

Area of allowable opening, AOP = (AEX + (AIN / 2)) × %Op For example consider Side B, Option 5: single sheathed with 100mm nail centres:

AOP = (18.24m2 + (14.4m2/2)) × 15% AOP = 3.82m2

Therefore %Op = (3.82m2 / 18.24 m2) × 100 = 21%

The table can therefore be revised as follows allowing for internal racking walls effect Side

Racking Band

Wall Options

Approximate allowable % opening per level per side

Side A R4 1. Single sheathed with 100mm nail centres 2. Single sheathed with 150mm nail centres

28 21

Side B R5 3. Single sheathed with 100mm nail centres 4. Single sheathed with 150mm nail centres

21 14

Wall studs From table to 1.E.19 , horizontal load category is H1 From table 1.E.20 , imposed load =1.00 kN/m2 leading to vertical load category = V17 From table 1 to 1.E.21 select 38x 140, grade wall stud at 600mm spacing Cripple studs For load V17 and 1200 mm opening ,table 1 to 1.E.22 gives 1 no 38 x 140 cripple studs grade C16 each side of opening Lintels For load V17 and 1200 mm opening ,table 2 ,to 1.E.23 gives 3 no 44x220, grade C24 lintels


1.E.25 Overall Stability To ensure there is an adequate factor of safety against overturning or sliding of a building with timber frame walls when subjected to the various loads and load combinations all parts of the walls require to be proportioned and connected as set out in this Annex including connections to floors, roofs and under building. It is also to be noted that the stability of the building during construction is to be considered. 1.E.26 Maximum allowable length and height of wall This Annex does not deal with walls longer than 12 m, measured from centre to centre of buttressing walls, providing restraint, or of walls exceeding 10 m in height. Construction materials and workmanship 1.E.27 General The construction materials and methods are restricted to those materials, timber strength classes, specifications, and dimensions which are most commonly used in Scotland for simple platform timber frame buildings as shown on the diagram below. Typical timber frame wall panel

panel le

ngth

Sheathing

Stud depth plus sheathing

Plastic tape or similar locates studpositions for wall tie fixing Breather membrane (may be site or factory fixed )

Bottom railStuds

Dwang (if required may be siteor factory fixed)

Panel height


1.E.28 Wall ties Wall ties should comply with BS EN 845-1 and be material references 1 or 3 in BS EN 845 Table A1 austenitic stainless steel. The type of tie should be selected by reference to DD 140-2: type 5(timber frame) or type 6(timber frame high movement) relevant to the performance levels given in DD140-2. Ties should permit vertical flexibility to permit vertical downward of timber frame in relation to the masonry cladding on the basis of differential movement of 6 mm/ storey height. Reference should also be made to 1.D.16 with respect to the masonry cladding and in particular to notes 1 and 2.


1.E.29 Masonry Cladding A typical masonry clad timber frame wall is illustrated below

Dwang to window opening Studs

Internal wall lining

Cripple stud to supportlintel over ceiling

Cavity barrier or batten for fixing windowVertical dpc

Thermal insulation

Sheathing Breather membraneFlexible wall tie, nailed to studs

Sole plate dpc

Inner leaf of brickwork or concrete block

Finished ground level

Masonry claddingVented cavity

Floor dpm lapped over wall and dressed under dpc

Bottom rail


1.E.30 Brick and block construction Brick and block used as masonry cladding should be in accordance with Annex 1.D in particular 1.D17-21 and should be in accordance with BS 5628 parts 1-3 , at least 100 mm thick with a minimum density of 7.36 kN/m3

1.E.31 Mortar Mortar used as masonry cladding should be in accordance with Annex 1.D in particular 1.D.22

1.E.32 Lintels for masonry cladding Proprietary steel or concrete lintels suitable for use with masonry cladding to timber frame construction should have independent certification and be in accordance with the manufacturer’s recommendations. Under no circumstances should the weight of masonry walls be transferred to the timber frame. 1.E.33 Timber members Timber studs, bottom and top rails ,sole plates head binders , cripple studs, lintels etc should be dry graded and marked timber of species and grade combinations to satisfy strength classes C16 or C24 to BS 5268: Part 2: 2002. The cross sectional dimensions given in this Annex are : a. CLS or ALS sizes in accordance with BS EN 336:2003 ,Table NA .5 to tolerance class 2; or b. equivalent timbers with dimensions in accordance with BS EN 336:2003 ,Table NA .4 to tolerance

class 2 ( but should not have lesser dimensions to those in a above ) c. Although 38 mm widths are provided in the tables above for studs, cripple studs and lintels 44 mm

width timbers are commonly used to provide an increased width to which plasterboard can be fixed.

1.E.34 Wall Sheathing Plywood used as sheathing to timber frame should be 9.5 mm minimum thickness of species and grade as defined in BS 5268: Part 2: 2002 ,Bonding Class 2 or 3 to BS EN 314-2 Oriented Strand Board used as sheathing to timber frame should be 9.0 mm minimum thickness,


Type OSB 3: Load bearing boards for use in humid conditions to BS EN 300 Oriented Strand Board Plasterboard used as wall linings and contributing to the structure of timber frame walls should be 12.5 mm minimum thickness for stud centres not more than 600 mm to BS 1230-1 . 1.E.35 Fasteners All structural fasteners should be corrosion resistant and checked for compatibility with preservative, treatments used and any other metalwork with which they are in contact. Nails should be manufactured from mild or stainless steel and be of round head or “D” head configuration to the diameter and length stated. 1.E.36 Fabrication Timber frame walls should be fabricated, assembled and erected in accordance with section 6 of BS 5268-6.1. Timber members in wall panels should be not less than 38 mm × 72 mm rectangular section with linings fixed to the narrower face, with ends cut square. Masonry cladding should be constructed on to the building foundation and tied back to the timber frame structure with a nominal cavity width of 50 mm between the inside face of the masonry cladding and the outer face of the timber frame wall. 1.E.37 Composite Action To ensure that timber frame walls act in a composite manner they must be constructed in accordance with 1.E.36 and 1.E.38 ensuring that sheathings and linings are nailed to all perimeter and intermediate timber members as on the diagram below. Sheathing edges should be backed by, and nailed to timber framing at all edges and where sheathing is nailed to studs; the nails should be not less than 7 mm from the edge of the board or the face of the stud. For plasterboard linings nails should be not less than 10 mm from formed board edges and not less than 13 mm from ends of the board at a spacing not exceeding 150 mm. Internal walls which are lined with plasterboard should be connected to the wall studs at the same perimeter nail spacing as the external sheathing material.

Perimeter Nailing Diagram

1.E. 38 Wall Panel Connections Where wall panels are combined to form the lengths of wall given it is essential that the following conditions are met to ensure that the coupled panels should be able to resist overturning forces:


1. Tops and bottoms of individual wall panels are linked by a head binder and sole plate respectively that are continuous across panel joints including at junctions of the same dimensions as the top and bottom rails by means of 3.75 mm nails of length 75 mm nails at 600 mm centres.

2. The sole plates should be secured to either the concrete floor slab or the header joists in the case of a timber ground floor or the header joists of the intermediate floor

3. The header plates should be secured to the header joists of the intermediate floor or the roof trusses.

4. The faces of end studs of contiguous panels are fixed such that any vertical shear is transferred. In the absence of more specific information, this should be by 3.35mm nails of length 75mm at 300mm centres.

5. All edges including to openings for windows, doors etc other than the bases of door openings and small openings should be supported by members having a thickness not less than the thickness of the studs.

6. The wall diaphragm details derived by following this guidance assume that the walls under consideration are adequately fixed to ensure resistance to sliding and overturning.

7. Where a secondary board is fixed on the same side of a wall as the primary sheathing then the nail lengths given in the table should be increased to take account of the additional thickness

A means should be provided of transferring horizontal forces in the plane of the panel above and below openings. Where no such provision is made, the wall lengths on either side of the opening should be designed as separate parts. 1.E.39 Nailing and fixing schedule Item Proposed Foundations Sole plate to underbuilding 4.7 kN shear resistance fixings at 600 mm centres Holding Down Straps Stainless steel strap 30 mm x 2.5 mm attached to stud by 6

no 65x3.35 ring shank nails at 2400 centres L shaped end of strap under masonry cladding

Wall Panels Top rail of Panels to head binders Tops of individual wall panel members linked by member

continuous across panel joints secured with 90x4.00mm galvanised wire nails, 2 nails between stud centres

Sole plate to ring beam/ joist 90x4.00mm galvanised wire nails, 2 nails between stud centres.

Bottom rail to sole plate 90x4.00mm galvanised wire nails, 2 nails between stud centres..

Wall Panel stud to wall panel stud 90x4.00mm galvanised wire nails, at 600mm centres each side staggered.

Header plate to Intermediate floor 90x4.00mm Galvanised wire nails at 300mm centres maximum. Nails skewed externally through rimboard into headbinder, and internally, skewed through the headbinder into the joists.

Perimeter Studs to sheathing 3.00mm x 50 mm wire nails 100 or 150 mm c/c as calculated Intermediate studs to sheathing 3.00mm x 50 mm wire nails 2x perimeter spacing as

calculated Studs to plasterboard 2.65 mm x 40mm Smooth shanked galvanised flat round

headed nails min , max 150 mm c/c Top and bottom rails to studs 2 no 90 mm nails end fixed


1. Multi-cripple studs should be secured to each other with 3.1mm dia. ×

64mm long galvanised ringshank nails at 400mm centres staggered mid distance between edge and centreline with no nail closer than 60mm to end of studs.

2. Lintels should be secured to each other with 3.1mm dia. × 75mm long galvanised screws at 300mm centres staggered mid distance between edge and centreline with no screw closer than 60mm to end of lintel.

300 mm

3. Holding down straps should be provided at 2.4m centres, at every opening and at the end studs

of a wall attached to the studs in a manner to provide at least 3.5kN of resistance. This is normally achieved by using 6 no 65x35mm ring shank nails or equivalent attaching the strap to the stud and placing the L-shaped end of the strap under the masonry cladding creating the holding down resistance.

Loadings on walls 1.E.40 Maximum span of floors The maximum span for any floor supported by a wall should be 6.0 m, where the span is measured centre to centre of bearing as opposite.

Masonry

Floor deck

Head binder

Floor span max 6mPacker


Floor member bearing on wall 1.E.41 Other loading conditions a. Vertical loading on walls such as timber floors and flat roofs designed in accordance with Annex

1.F, timber roof trusses. b. The combined dead and imposed load should not exceed 70kN/m at base of wall c. Timber frame walls should commence above ground level and therefore should not be subject to

lateral loads other than from wind .


1.E.42 End restraint The wind load is resisted primarily by transfer directly to the foundations at the base of the wall and by the racking resistance of the timber frame supporting walls, the load having been transferred via the floor and ceiling diaphragms. The ends of every wall should be securely tied throughout their full height to walls which are providing racking resistance. Normally supporting walls are the external walls perpendicular to the wall subject to wind load and are designed as racking walls. The use of internal walls to provide additional racking resistance is outwith the scope of this Annex and specialist advice should be obtained. Openings, notching and drilling 1.E.43 General The number, size and position of openings must not impair the stability of a wall or the lateral support afforded to a supported wall. Construction over openings must be adequately supported. 1.E.44 Framing of openings a. Lintels supporting masonry cladding over openings should be structurally independent of the timber frame ensuring no loads from the masonry cladding are carried by the timber frame. b. Loads over openings in timber frame wall panels are carried independently by timber lintels. Lintels should be supported by cripple studs as shown opposite and the lintel loads carried down on to the floor below.

cripplestuds


1.E.45 Dimensional criteria for openings and recesses The dimensional criteria are given in the diagram to 1.F.15 No openings should be provided in walls below ground floor except for small holes for services and ventilation etc. which should be limited to a maximum area of 0.1 m2 at not less than 2 m centres . 1.E.46 Small unframed openings The size and position of small openings should be restricted as follows: a) not exceed 250mm in diameter or in length of side; and b) clear distance between openings should be not less than the greatest dimension of the openings;

and c) clear distance between the edge of sheathing and the edge of any opening should be not less

than the greatest dimension of the opening; and d) not more than one such opening should occur in any one 600mm width of sheathing or lining. Smaller unframed openings may occur to a greater extent, but their aggregate opening area should not exceed the total area of opening given in item a). The rules governing the position of openings given in items b), c) and d) should also apply.


1.E.47 Notching & drilling Holes should be within the limits set out opposite and as follows : • holes should be drilled at the neutral axis • holes should be not less than 300mm

apart Notching is not permitted in wall studs, cripple studs and lintels.

D

H

max 0.25 D

0.25H

0.25H

0.4H

0.4H

holes on centrelineonly. Hole diameternot greater than 0.25Dand not closer than 300mm

1.E.48 Lateral support by roofs and floors The wall panels in each storey of a building should extend to the full height of that storey, and be connected the floors and roofs to provide adequate diaphragm action and transfer lateral forces from the walls to the racking walls ,be of normal construction and: a. intermediate floors require the floor deck or sub-deck fixed directly to the top faces of the joists,

or the floor braced by some other means b. pitched roofs require the plasterboard ceiling to be fixed directly under the roof, together with the

roof bracing recommended in BS5268-3 c. be secured to the supported wall by connections specified in clause 1.E.39

1.E.49 Differential movement Allowance should be made for differential movement particularly vertical movement between timber frame walls and masonry cladding. The allowances opposite are based upon: a. conventional platform frame construction b. concrete ground floor c. 200 mm deep intermediate floor joists d. installed timber moisture content of 20 % drying

to 10% If timber ground floors are used then add 8 mm to all allowances shown opposite For a timber frame extension connected to an existing traditional masonry wall the roof to the extension should be supported on a timber bearer connected to the existing wall to minimise the differential movement in the supports to the extension roof .

allowance at eavesand verge


Annex 1.F Timber floor and roof members

1.F.0 Introduction 1.F.1 The use of this Annex 1.F.2 Common timber species/grade combinations 1.F.3 Notches and holes 1.F.4 Strutting to Joists Loadings 1.F.5 Dead loads 1.F.6 Imposed roof loads including snow Spans, sizes and spacings for timber members 1.F.7 General 1.F.8 Floor joist tables 1.F.9 Joists for flat roofs tables for maintenance or repair purposes 1.F.10 Joists for flat roofs tables not limited to maintenance or repair

purposes 1.F.11 Raised tie roofs 1.F.12 Collared roofs 1.F.13 Connections for raised tie and collared roofs

contents


annex

1.F Sizes of certain timber floors and roof members

1.F.0 Introduction This Section applies only to domestic buildings with the exception of flats and maisonettes of not more than three storeys. Where trussed rafters are used reference should be made to BS 5268: Part 3: 1998 for design and bracing recommendations. 1.F.1 The use of this Annex This Annex should be used in conjunction with Annex 1.B The guidance given in this Annex assumes that - a. the dead and imposed loads to be sustained by the floor, ceiling, or roof of which the member

forms part, do not exceed the values given in the notes to the appropriate diagrams and tables; b. the species and grade of timber for the strength class to which the table to 1.F.2 relates is

either: • as in 1.F.2 for more common species, or • as in the more comprehensive tables of BS 5268: Part 2: 2002; and

c. that floorboarding complying with BS 1297: 1987 or moisture resistant wood chipboard type P5 complying with BS EN 312 is used.

d. the strength classes, species, grades and species combinations are as defined in BS 5268: Part 2: 2002.

e. the cross sectional dimensions are : • CLS or ALS sizes in accordance with BS EN 336:2003 ,Table NA .5, tolerance class 2; • equivalent timbers to dimensions in accordance with BS EN 336:2003 ,Table NA .4 ,tolerance

class 2 but not lesser dimensions to those above The tables do not apply where these dimensions have been reduced, in the case of tables to 1.F.8 by planing and in the case of tables to 1.F.9 by planing or regularising. For timber of North American origin the tables only apply as indicated to surfaced sizes unless the timber has been resawn to BS EN 336 requirements. Bearing areas and workmanship should comply with the relevant requirements of BS 5268: Part 2: 2002. Refer also to clauses 1.D.34-36 or clauses 1.E.48 respectively for masonry and timber frame walls.


1.F.2 Common species/grade combinations satisfying the strength classes to which 1.F.8-12 relates. Grades to satisfy strength

Species Origin Grading rule C16 C24 All species listed in this table

BS EN 519 machine graded to C16 machine graded to C24

Imported Redwood or Whitewood

BS 4978 GS SS

Douglas Fir UK BS 4978 SS - Larch SS -

British Pine SS - British Spruce SS - Douglas Fir-Larch Canada BS 4978 GS SS Hem-Fir GS SS Spruce-Pine-Fir GS SS Sitka spruce SS - Douglas Fir-Larch Canada NLGA Joist & plank No 1 & 2

Structural L.F. No 1 & 2 Joist & plank select Structural L.F select

Hem-Fir Joist & plank No 1 & 2 Structural L.F. No 1 & 2

Joist & plank select Structural L.F select

Spruce-Pine-Fir Joist & plank No 1 & 2 Structural L.F. No 1 & 2


Sitka spruce Joist & plank select Structural L.F

-

Douglas Fir-Larch Canada MSR 1450f-1.3E 1800f-1.6E Hem-Fir 1450f-1.3E 1800f-1.6E Spruce-Pine-Fir 1450f-1.3E 1800f-1.6E Douglas Fir-Larch USA BS 4978 GS SS Hem-Fir GS SS Southern Pine GS SS Spruce-Pine-Fir GS SS Western Whitewoods

SS -

Douglas Fir-Larch USA NGRDL Joist & plank No 1 & 2 Structural L.F. No 1 & 2


Hem-Fir Joist & plank No 1 & 2 Structural L.F. No 1 & 2


Spruce-Pine-Fir Joist & plank No 1 & 2 Structural L.F. No 1 & 2


Western Whitewoods

Joist & plank select Structural L.F

-

Southern Pine Joist & plank No 3 Stud grade

Joist & plank select

Douglas Fir-Larch USA MSR 1450f-1.3E 1800f-1.6E Hem-Fir 1450f-1.3E 1800f-1.6E Southern Pine 1450f-1.3E 1800f-1.6E Spruce-Pine-Fir 1450f-1.3E 1800f-1.6E 1 The species/grade combinations given in this Table are for particular use with the other Tables in this Annex and for the cross section sizes given in those Tables. 2 The grading rules for American and Canadian Lumber are those approved by the American Lumber Standards Board of Review and the Canadian Lumber Standards Accreditation Board respectively (see BS 5268: Part 2: 2002).


1.F.3 Notches and holes Notches and holes in simply supported floor and flat roof joists should be within the limits set out below and as follows : holes should be drilled at the neutral axis notches and holes should be not less than 100mm apart horizontally; notches may be at the top or bottom of a joist but not coinciding. notches should not be cut in rafters, purlins or binders unless approved by the building designer

0.25L min0.07L minMax D/8 0.07L min

0.4L min

1.F.4 Strutting to Joists Floor joists spanning more than 2.5m should be strutted by one or more rows of solid as shown in the following table. Solid timber strutting should be at least 38mm thick extending at least 3/4 depth of joist.

Joist span m

Number of rows of strutting

Position

Less than 2.5 none

2.5 to 4.5 1 at mid span

more than 4.5 2 at one third span

Loading 1.F.5 Dead floor and roof loads Construction Dead load

( kN/m2 ) Floors Floor boards , 13 mm plasterboard 0.22 Floor boards , 19 mm plasterboard 0.27 Floor boards , ash deadening, lath &plaster 1.18 Flat roofs 3 layer felt , 16 mm decking , 100mm mineral wool , vapour layer , 13 mm plasterboard

0.32

13 mm chippings ,50 mm rigid insulation , vapour layer, 19 mm decking , 13 mm plasterboard

0.6

13 mm chippings , 19 mm mastic asphalt , decking , 100 mm mineral wool ,vapour layer, 13 mm plasterboard

0.90

Note that the above is based on 600 mm joist spacing and excludes the weight of the joists and any partitioning


1.F.6 Imposed roof loads including snow The map opposite indicates the zones within Scotland where the snow loading on flat roofs is not expected to exceed the values set out in the table below of 0.75, 1.00 or 1.5 kN/m2, depending on geographical location and altitude.

This guidance applies only to pitched and free-standing flat roofed structures with the roof on one level only within the limits set out on the tables to clauses 1.F.8-12, provided that there are no other buildings within 1.5m of its perimeter but does not apply to trussed rafter roofs.

For all other circumstances, reference should be made to BS 6399: Part 3: 1988: Code of Practice for Imposed Roof Loads.

Inverness

Zone AB

Zone Imposed roof loads ( kN/m2 ) Altitudes below 100m Altitudes between

100m and 200 m Altitudes between 200m and 260 m

A 0.75 1.00 Refer to BS 6399: Part 3

B 1.00 1.50 1.5


Spans, sizes and spacings for timber members 1.F.7 General The following Table refers to further tables and diagrams with accompanying notes that give spans, sizes and spacings for certain timber floor and flat roof and pitched roof members .In clauses 1.F.8-12 all spans, except those for floorboards, are measured as the clear dimensions between supports, and all spacings are the dimensions between longitudinal centres of members.

Key to Tables relating to timber members

Construction Timber members

Table numbers for strength classes

C16 C24

Floors joists 1.F.8 1.F.8 Flat roofs access for maintenance only full access allowed

joists joists

1.F.9 1.F.10

1.F.9 1.F.10

Raised tie roofs All 1.F.11 1.F.11

Collared roofs All 1.F.12 1.F.12 1.F.8 Floor joists The tables below give sizes, spacings and spans for floor joists which will support the dead loads given in the Tables and an imposed load not exceeding 1.5kN/m2. Partition loads have not been allowed for Softwood tongued and grooved floorboards if supported at a joist spacing of up to 450mm shall be at least 16mm thick; and if supported at wider spacings up to 600mm should be 19mm thick. Wood chipboard, type P5, if supported at a joist spacing of up to 450mm shall be at least 18mm thick and if supported at wider spacing up to 600mm shall be 22mm thick. Floor joists selected from these tables may be used for intermediate floors in timber frame construction but will require header joists around the perimeter. T & G Chipboard flooring should be fixed by 3.35 mm 65 mm angular ring shank nails at 200 mm c/c perimeter and 300 mm intermediate and recommended to be glued by PVA adhesive between boards and joists to boards to prevent creaking ( per BS 8103-3)


Permissible clear spans of joists supporting floors with no partitions. Timber of strength class C16

Dead load kN/m2

Not more than 0.25

More than 0.25 but not more than 0.50


Spacing of joists mm

Size of joist

400 450 600 400 450 600 400 450 600 mm× mm Maximum clear span of joist

m BS EN 336 sizes 38 × 97 38 × 122 38 × 147 38 × 170 38 × 195 38 × 220

1.828 2.482 2.983 3.442 3.939 4.434

1.692 2.385 2.868 3.306 3.752 4.193

1.303 1.925 2.510 2.873 3.263 3.648

1.717 2.368 2.853 3.281 3.724 4.161

1.556 2.215 2.707 3.098 3.518 3.932

1.214 1.755 2.331 2.690 3.056 3.418

1.423 1.947 2.453 2.808 3.189 3.567

1.301 1.791 2.290 2.649 3.010 3.367

1.037 1.448 1.872 2.267 2.609 2.920

47 × 72 47 × 97 47 × 122 47 × 147 47 × 170 47 × 195 47 × 220

1.324 2.024 2.663 3.200 3.691 4.221 4.723

1.233 1.914 2.561 3.078 3.551 4.063 4.572

0.942 1.583 2.302 2.786 3.188 3.619 4.044

1.272 1.920 2.548 3.062 3.533 4.042 4.549

1.154 1.818 2.450 2.945 3.398 3.889 4.354

0.891 1.460 2.087 2.609 2.987 3.391 3.791

1.091 1.665 2.255 2.723 3.116 3.538 3.954

0.993 1.527 2.081 2.570 2.942 3.341 3.735

0.783 1.228 1.696 2.174 2.552 2.900 3.244

63 × 97 63 × 122 63 × 147 63 × 170 63 × 195 63 × 220

2.319 2.931 3.518 4.055 4.633 5.061

2.197 2.821 3.388 3.905 4.465 4.923

1.919 2.566 3.084 3.558 4.070 4.580

2.191 2.807 3.370 3.886 4.442 4.905

2.079 2.700 3.244 3.741 4.278 4.770

1.822 2.454 2.950 3.404 3.896 4.365

1.934 2.527 3.037 3.504 4.009 4.512

1.839 2.429 2.920 3.370 3.850 4.301

1.533 2.088 2.577 2.950 3.350 3.745

75 × 122 75 × 147 75 × 170 75 × 195 75 × 220

3.100 3.719 4.283 4.830 5.268

2.985 3.582 4.128 4.700 5.128

2.718 3.265 3.765 4.306 4.793

2.970 3.564 4.107 4.683 5.109

2.859 3.432 3.957 4.523 4.971

2.601 3.125 3.605 4.125 4.641

2.677 3.216 3.709 4.242 4.740

2.575 3.094 3.569 4.084 4.595

2.327 2.807 3.212 3.646 4.074

CLS/ALS sizes 38 × 89 38 × 140 38 × 184 38 × 235

1.617 2.843 3.721 4.710

1.463 2.733 3.557 4.460

1.121 2.398 3.092 3.890

1.499 2.719 3.530 4.430

1.356 2.587 3.334 4.180

1.052 2.167 2.895 3.640

1.259 2.330 3.022 3.800

1.149 2.149 2.852 3.590

0.910 1.752 2.471 3.110


Permissible clear spans of joists supporting floors with no partitions. Timber of strength class C24

Dead load kN/m2

Not more than 0.25




Size of joist

400 450 600 400 450 600 400 450 600 mm× mm Maximum clear span of joist

m BS EN 336 sizes 38 × 97 38 × 122 38 × 147 38 × 170 38 × 195 38 × 220

1.936 2.582 3.103 3.580 4.096 4.609

1.829 2.482 2.984 3.444 3.941 4.436

1.586 2.200 2.709 3.128 3.581 4.034

1.838 2.469 2.969 3.426 3.921 4.413

1.739 2.369 2.854 3.294 3.771

4.246

1.514 2.076 2.588 2.989 3.423

3.856

1.635 2.180 2.667 3.079 3.526 3.971

1.551 2.073 2.561 2.958 3.388 3.816

1.358 1.826 2.305 2.678 3.068 3.458

47 × 72 47 × 97 47 × 122 47 × 147 47 × 170 47 × 195 47 × 220

1.404 2.141 2.770 3.327 3.836 4.387 4.860

1.324 2.025 2.664 3.201 3.693 4.224 4.725

1.144 1.763 2.421 2.910 3.359 3.845 4.328

1.347 2.026 2.651 3.185 3.674 4.202 4.707

1.273 1.920 2.549 3.064 3.535 4.045 4.552

1.103 1.678 2.290 2.783 3.212 3.678 4.141

1.223 1.795 2.382 2.865 3.307 3.786 4.262

1.159 1.705 2.268 2.754 3.179 3.640 4.099

1.010 1.499 2.006 2.496 2.883 3.302 3.720

63 × 97 63 × 122 63 × 147 63 × 170 63 × 195 63 × 220

2.432 3.046 3.665 4.211 4.770 5.204

2.321 2.933 3.521 4.058 4.637 5.064

2.030 2.669 3.207 3.699 4.231 4.731

2.308 2.918 3.503 4.037 4.614 5.046

2.192 2.808 3.372 3.888 4.445 4.908

1.925 2.553 3.069 3.541 4.052 4.560

2.032 2.628 3.158 3.643 4.168 4.678

1.934 2.527 3.038 3.505 4.011 4.514

1.709 2.273 2.759 3.185 3.646 4.106

75 × 122 75 × 147 75 × 170 75 × 195 75 × 220

3.220 3.862 4.446 4.966 5.415

3.102 3.721 4.286 4.833 5.272

2.827 3.394 3.913 4.474 4.932

3.086 3.703 4.265 4.816 5.253

2.972 3.567 4.110 4.686 5.113

2.705 3.250 3.748 4.287 4.778

2.784 3.344 3.855 4.408 4.878

2.678 3.218 3.711 4.245 4.743

2.433 2.925 3.376 3.864 4.350

CLS/ALS sizes 38 × 89 38 × 140 38 × 184 38 × 235

1.713 2.957 3.869 4.850

1.617 2.844 3.723 4.710

1.399 2.581 3.382 4.310

1.633 2.829 3.703 4.700

1.544 2.719 3.561 4.540

1.341 2.466 3.232 4.120

1.464 2.541 3.329 4.240

1.388 2.440 3.199 4.080

1.201 2.170 2.897 3.700


1.F.9 Joists for flat roofs with access only for the purposes of maintenance or repair The tables below give sizes, spacings and spans for flat roof joists designed for access only for maintenance which will support the dead loads given in the Tables and an imposed load not exceeding 0.75 kN/m2 or an imposed concentrated load of 0.9KN.

Span of roof jo

ists

The tables are fora slope of up to 10 from the horizontal

support

Roofjoist

Roof joistspacing

Joists for flat roofs with access only for the purposes of maintenance or repair Timber of strength class C16.

Dead load kN/m2

Not more than 0.5



Spacing of joists (mm) 400 450 600 400 450 600 400 450 600

Size of joist mm× mm

Maximum clear span of joist m

BS EN 336 sizes 38 × 97

38 × 122 38 × 147 38 × 170 38 × 195 38 × 220

1.738 2.368 3.020 3.631 4.303 4.943

1.719 2.336 2.974 3.571 4.226 4.762

1.666 2.250 2.851 3.368 3.855 4.340

1.666 2.250 2.851 3.412 4.025 4.641

1.642 2.212 2.797 3.342 3.939 4.491

1.578 2.113 2.659 3.166 3.629 4.087

1.605 2.155 2.717 3.239 3.810 4.383

1.578 2.113 2.659 3.166 3.719 4.274

1.507 2.005 2.511 2.980 3.446 3.881

47 × 72 47 × 97

47 × 122 47 × 147 47 × 170 47 × 195 47 × 220

1.272 1.919 2.602 3.304 3.960 4.677 5.282

1.260 1.896 2.565 3.252 3.892 4.530 5.093

1.229 1.835 2.468 3.115 3.612 4.132 4.649

1.229 1.835 2.468 3.115 3.716 4.372 4.991

1.214 1.808 2.425 3.055 3.639 4.277 4.808

1.175 1.735 2.313 2.900 3.402 3.893 4.383

1.192 1.765 2.360 2.964 3.525 4.136 4.747

1.175 1.735 2.313 2.900 3.444 4.037 4.577

1.130 1.654 2.192 2.736 3.232 3.700 4.166

63 × 97 63 × 122 63 × 147 63 × 170 63 × 195 63 × 220

2.190 2.948 3.722 4.439 5.141 5.771

2.162 2.905 3.662 4.345 4.961 5.572

2.088 2.790 3.444 3.969 4.537 5.101

2.088 2.790 3.503 4.161 4.864 5.464

2.055 2.740 3.434 4.074 4.689 5.270

1.968 2.609 3.246 3.744 4.282 4.816

2.005 2.664 3.330 3.945 4.612 5.212

1.968 2.609 3.256 3.853 4.468 5.024

1.873 2.469 3.069 3.561 4.074 4.585

75 × 122 75 × 147 75 × 170 75 × 195 75 × 220

3.168 3.984 4.736 5.415 6.000

3.121 3.919 4.583 5.229 5.869

2.995 3.640 4.194 4.791 5.383

2.995 3.747 4.439 5.129 5.758

2.940 3.672 4.334 4.949 5.558

2.797 3.435 3.959 4.526 5.088

2.857 3.561 4.208 4.894 5.497

2.797 3.481 4.110 4.719 5.303

2.645 3.268 3.768 4.310 4.847

CLS/ALS sizes 38 × 89

38 × 140 38 × 184 38 × 235

1.543 2.836 4.007 5.271

1.528 2.794 3.937 5.078

1.484 2.682 3.641 4.630

1.484 2.682 3.755 4.975

1.464 2.633 3.676 4.790

1.410 2.505 3.427 4.360

1.433 2.559 3.559 4.726

1.410 2.505 3.476 4.556

1.350 2.369 3.254 4.142


Joists for flat roofs with access only for the purposes of maintenance or repair Timber of strength class C24.

Dead load kN/m2

Not more than 0.5

More than 0.5 but not more

than 0.75



400 450 600 400 450 600 400 450 600



BS EN 336 sizes 38 × 97

38 × 122 38 × 147 38 × 170 38 × 195 38 × 220

1.837 2.496 3.177 3.814 4.512 5.134

1.816 2.462 3.128 3.750 4.399 4.947

1.759 2.370 2.997 3.503 4.009 4.512

1.759 2.370 2.997 3.580 4.218 4.847

1.733 2.329 2.939 3.507 4.127 4.668

1.664 2.223 2.792 3.298 3.775 4.251

1.693 2.267 2.853 3.398 3.991 4.586

1.664 2.223 2.792 3.320 3.895 4.441

1.588 2.108 2.635 3.123 3.586 4.039

47 × 72 47 × 97

47 × 122 47 × 147 47 × 170 47 × 195 47 × 220

1.347 2.025 2.739 3.472 4.153 4.879 5.482

1.334 2.001 2.700 3.416 4.081 4.704 5.287

1.300 1.935 2.596 3.256 3.755 4.294 4.831

1.300 1.935 2.596 3.269 3.894 4.575 5.182

1.284 1.905 2.549 3.205 3.813 4.441 4.995

1.241 1.826 2.430 3.041 3.538 4.048 4.556

1.259 1.860 2.480 3.110 3.693 4.327 4.938

1.241 1.826 2.430 3.041 3.607 4.223 4.756

1.192 1.740 2.301 2.868 3.363 3.849 4.333

63 × 97 63 × 122 63 × 147 63 × 170 63 × 195 63 × 220

2.307 3.098 3.903 4.645 5.332 5.983

2.277 3.052 3.838 4.509 5.147 5.779

2.198 2.929 3.578 4.123 4.712 5.296

2.198 2.929 3.670 4.353 5.047 5.668

2.162 2.876 3.597 4.261 4.868 5.470

2.069 2.736 3.375 3.891 4.449 5.003

2.108 2.795 3.487 4.125 4.816 5.409

2.069 2.736 3.409 4.029 4.640 5.216

1.968 2.588 3.212 3.702 4.235 4.764

75 × 122 75 × 147 75 × 170 75 × 195 75 × 220

3.325 4.172 4.924 5.612 6.000

3.274 4.103 4.754 5.422 6.000

3.141 3.781 4.354 4.973 5.585

3.141 3.921 4.638 5.319 5.969

3.082 3.842 4.498 5.135 5.765

2.931 3.569 4.113 4.700 5.283

2.994 3.725 4.396 5.078 5.703

2.931 3.641 4.289 4.899 5.503

2.770 3.397 3.916 4.477 5.035


38 × 140 38 × 184 38 × 235

1.633 2.985 4.205 5.473

1.615 2.940 4.131 5.275

1.568 2.820 3.787 4.813

1.568 2.820 3.937 5.169

1.546 2.768 3.854 4.979

1.488 2.632 3.566 4.535

1.513 2.689 3.730 4.921

1.488 2.632 3.642 4.737

1.424 2.487 3.387 4.310


1.F.10 Joists for flat roofs access not limited to maintenance or repair purposes The tables below give sizes, spacings and spans for flat roof joists designed for access not limited to maintenance or repair purposes which will support the dead loads given in the Tables and an imposed load not exceeding 1.5 kN/m2 or an imposed concentrated load of 1.8 kN. Span of ro

of joists

The tables are fora slope of up to 10 from the horizontal

support

Roofjoist

Roof joistspacing

Joists for flat roofs access not limited to maintenance or repair purposes Timber of strength class C16. Dead load kN/m2 Not more than 0.5



Spacing of joists (mm) 400 450 600 400 450 600 400 450 600 Size of joist mm× mm


BS EN 336 sizes 38 × 97 38 × 122 38 × 147 38 × 170 38 × 195 38 × 220

1.211 1.798 2.347 2.876 3.470 4.078

1.202 1.785 2.327 2.848 3.432 4.030

1.176 1.736 2.272 2.771 3.293

3.710

1.176 1.736 2.272 2.771 3.329

3.897

1.164 1.712 2.246 2.736 3.282

3.838

1.130 1.647 2.177 2.641 3.156

3.564

1.145 1.675 2.207 2.681 3.210

3.747

1.130 1.647 2.177 2.641 3.156

3.680

1.090 1.573 2.088 2.533 3.017

3.430 47 × 72 47 × 97 47 × 122 47 × 147 47 × 170 47 × 195 47 × 220

0.869 1.436 2.000 2.601 3.176 3.820 4.477

0.864 1.428 1.986 2.578 3.144 3.777 4.383

0.850 1.404 1.944 2.513 3.056 3.539 3.986

0.850 1.404 1.944 2.513 3.056 3.659 4.271

0.844 1.363 1.925 2.484 3.015 3.605 4.204

0.825 1.362 1.871 2.403 2.907 3.401 3.831

0.833 1.375 1.894 2.438 2.953 3.524 4.102

0.825 1.362 1.871 2.403 2.907 3.463 4.027

0.802 1.210 1.809 2.311 2.784 3.282 3.697

63 × 97 63 × 122 63 × 147 63 × 170 63 × 195 63 × 220

1.666 2.306 2.981 3.624 4.338 4.999

1.655 2.287 2.953 3.585 4.286 4.816

1.625 2.236 2.874 3.408 3.900 4.390

1.625 2.236 2.874 3.478 4.146 4.821

1.611 2.212 2.838 3.430 4.084 4.639

1.572 2.146 2.741 3.277 3.752 4.224

1.589 2.174 2.783 3.356 3.987 4.624

1.572 2.146 2.741 3.301 3.917 4.483

1.526 2.070 2.631 3.157 3.623 4.079

75 × 122 75 × 147 75 × 170 75 × 195 75 × 220

2.503 3.225 3.908 4.663 5.278

2.482 3.193 3.865 4.526 5.088

2.423 3.105 3.609 4.128 4.645

2.423 3.105 3.747 4.454 5.088

2.396 3.065 3.694 4.360 4.904

2.322 2.957 3.472 3.973 4.472

2.354 3.003 3.611 4.280 4.923

2.322 2.957 3.551 4.203 4.742

2.237 2.835 3.353 3.838 4.321

CLS/ALS sizes 38 × 89 38 × 140 38 × 184 38 × 235

1.038 2.190 3.206 4.449

1.032 2.173 3.173 4.360

1.012 2.123 3.082 3.960

1.012 2.123 3.082 4.242

1.003 2.101 3.040 4.175

0.977 2.038 2.929 3.804

0.988 2.065 2.976 4.072

0.977 2.038 2.929 3.996

0.946 1.942 2.803 3.647


Joists for flat roofs access not limited to maintenance or repair purposes Timber of strength class C24.

Dead load kN/m2

Not more than 0.5


More than 0.75 but notmore than 1.00


400 450 600 400 450 600 400 450 600



BS EN 336 size 38 × 97

38 × 122 38 × 147 38 × 170 38 × 195 38 × 220

1.367 1.908 2.486 3.041 3.663 4.299

1.359 1.895 2.464 3.011 3.622 4.247

1.337 1.856 2.404 2.928 3.429 3.862

1.337 1.856 2.404 2.928 3.511 4.104

1.327 1.838 2.377 2.889 3.460 4.041

1.298 1.788 2.301 2.787 3.294 3.711

1.311 1.809 2.333 2.831 3.383 3.943

1.298 1.788 2.301 2.787 3.326 3.872

1.263 1.729 2.214 2.671 3.176 3.580

47 × 72 47 × 97

47 × 122 47 × 147 47 × 170 47 × 195 47 × 220

0.982 1.526 2.120 2.751 3.354 4.026 4.711

0.978 1.517 2.104 2.725 3.319 3.980 4.556

0.966 1.490 2.058 2.656 3.216 3.682 4.147

0.966 1.490 2.058 2.656 3.223 3.853 4.491

0.960 1.478 2.037 2.623 3.179 3.795 4.385

0.944 1.444 1.979 2.536 3.062 3.540 3.987

0.951 1.459 2.004 2.573 3.112 3.708 4.310

0.944 1.444 1.979 2.536 3.062 3.643 4.230

0.924 1.403 1.911 2.437 2.931 3.417 3.849

63 × 97 63 × 122 63 × 147 63 × 170 63 × 195 63 × 220

1.766 2.439 3.146 3.818 4.561 5.191

1.754 2.418 3.116 3.776 4.449 5.003

1.722 2.362 3.030 3.544 4.055 4.564

1.722 2.362 3.030 3.661 4.357 5.003

1.706 2.336 2.992 3.609 4.289 4.820

1.663 2.265 2.887 3.409 3.902 4.393

1.682 2.295 2.931 3.529 4.187 4.839

1.663 2.265 2.887 3.471 4.112 4.660

1.613 2.183 2.769 3.292 3.769 4.243

75 × 122 75 × 147 75 × 170 75 × 195 75 × 220

2.644 3.399 4.111 4.785 5.477

2.261 3.364 4.065 4.700 5.283

2.557 3.253 3.751 4.291 4.827

2.557 3.269 3.938 4.673 5.283

2.528 3.226 3.881 4.529 5.093

2.448 3.110 3.611 4.131 4.648

2.482 3.160 3.794 4.489 5.113

2.448 3.110 3.729 4.380 4.927

2.356 2.980 3.488 3.991 4.493


38 × 140 38 × 184 38 × 235

1.203 2.321 3.387 4.686

1.197 2.302 3.351 4.535

1.180 2.248 3.238 4.122

1.180 2.248 3.253 4.464

1.171 2.223 3.208 4.362

1.148 2.155 3.088 3.961

1.158 2.185 3.139 4.282

1.148 2.155 3.088 4.202

1.119 2.077 2.953 3.822


1.F.11 Raised tie roof The tables below give member sizes for raised tie roofs designed for access limited to maintenance or repair purposes which will support dead load not exceeding 0.75 kN/m2 and an imposed load not exceeding 1.5 kN/m2 for truss centres of 400 , 450 and 600 mm

Maximum span 5000 mm

h30 - 55

Ridge

Sarking

RaftersTie Joist

Timber of strength class C16

Rafter Size mm×mm

Tie Joist Size mm×mm

h (max) mm

Span (max) mm

47×220 47×220 575 5,000 47×195 47×195 450 5,000

47×195 47×195 325 5,000

Timber of strength class C24( TR26) Rafter Size mm×mm

Tie Joist Size mm×mm

h (max) mm

Span (max) mm

47×170 or 38×195 47×170 or 38×195 575 5,000 38×195 38×195 450 5,000

38×195 38×195 325 5,000 Roof bracing to comply with BS 5268: part 3 Masonry walls to comply with Annex 1.D and be cavity walls comprising 100 mm thick 3.5 N/mm2 blockwork inner leaf and 102 mm thick brickwork outer leaf Connection details should be as in 1.F.13 Trusses to be tied down to walls in accordance with 1.E.39


1.F.12 Collared roof The tables below give member sizes for collared roofs designed for access limited to maintenance or repair purposes which will support dead load not exceeding 0.75 kN/m2 and an imposed load not exceeding 1.5 kN/m2 for truss centres of 400, 450 and 600 mm and spans of 6.0m and 7.5 m. Roof space is for ceilings for access only for an imposed load of 0.25 kN/m2 together with a concentrated load of 0.9kN and does not include for water tanks.

Maximum span 7500 mm

H

Ridge

H/2

Sarking

Rafters

CollarsHangers

Ceiling tie

Span not exceeding 7.5 m Timber of strength class C16

Centres mm

Rafter Size mm×mm

Ceiling Tie mm×mm

Collar Size mm×mm

Hanger Size mm×mm

400 47×147 47×147 47×97 47×97 450 47×195 47×195 47×122 47×122

600 47×220 47×220 47×147 47×147

Span not exceeding 7.5 m Timber of strength class C24( TR26)

Centres mm

Rafter Size mm×mm

Ceiling Tie mm×mm

Collar Size mm×mm

Hanger Size mm×mm

400 47×147 47×147 47×97 47×97 450 47×147 47×147 47×122 47×122

600 47×195 47×195 47×147 47×147 Roof bracing to comply with BS 5268: part 3 Masonry walls to comply with Annex 1.D and be cavity walls comprising 100 mm thick 3.5 N/mm2 blockwork inner leaf and 102 mm thick brickwork outer leaf Connection details should be as in 1.F.12 Trusses to be tied down to walls in accordance with 1.E.39


1.F.13 Connection details for raised tied and collared roofs Connections for raised and collared roofs should be as shown below Ceiling tie to rafter connection

Double sided toothed connector

Grade 4.6 bolt

a. Up to 450mm rafter centres: 38mm diameter double sided toothed connector and M10, grade 4.6 bolts should be used. b. Up to 600mm rafter centres: 51mm diameter double sided toothed connector and M12, grade 4.6 bolts should be used.

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