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Come inside...Ground Floors: Residential

Ground Floors: Residential

FloorsBuilding,Residential

Mar 2004CI/SfB m1

81 (13) Rn7 (M2)

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...From Thermal Insulation, giving energy efficiency

...from Acoustic Insulation, reducing sound transmission

...from Fire Resistant Products, increasing safety

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2

elements, but the improvement required

in floors has been the most marked.

To meet these new requirements

thicknesses of insulation have increased

greatly and this has necessarily

prompted designers to reconsider the

specification of insulation in ground

floors.

Ground floors fall predominantly into

two categories, ground bearing and

suspended. The type chosen by the

designer is largely dependent on site

conditions.

Recent changes to the thermal

requirements of the Building Regulations

have made it necessary to include

insulation in nearly all ground floors.

The thermal performance of ground

Overviewfloors is determined by a combination

of the thermal resistance of the floor

construction and the insulation provided

by the ground. Until the late 1990’s, the

thermal resistance of the uninsulated

floor and the ground was often sufficient

to meet Building Regulation

requirements. Recent changes have

required a significant improvement in

the thermal performance of all building

www.knaufinsulation.co.uk

3

AdvantagesBoth ground bearing and suspended

ground floors can offer excellent thermal

performance by including high levels of

insulation without dramatically altering

the building shape or geometry.

Ground bearing floors can include

insulation either below or above the

concrete slab, dependent on the choice

of the designer. If the insulation is

installed below the slab, this acts as a

thermal store, helping to maintain steady

temperatures in the building. If it is

installed above the slab, the building

will respond much more quickly to the

heating system.

Suspended floors are usually insulated in

such a way that they offer little thermal

mass and respond quickly to the heating

system. In the case of suspended

concrete, the insulation is installed above

the deck, either under a screed or timber

A beam and block suspended ground

floor under construction

boarding. Suspended timber floors are

normally insulated between the joists.

Floor insulation is of particular

importance if installing under floor

heating.

Knauf Insulation Products

• Polyfoam Floorboard Standard is a

high performance, 100% ozone

friendly, extruded polystyrene, rigid

board insulation. It is lightweight, yet

has excellent structural strength and

long term effectiveness. The boards

are square edged.

• Rocksil Floor Slab is a rigid,

compression resistant slab of

non-combustible rock mineral wool.

• Crown Loft Roll is made from glass

mineral wool and formed into

unfaced rolls which are lightweight,

flexible, resilient and non-

combustible.

Insulationtype

System Dimensions

0.20

0.25

0.30

0.35

0.40

150mm 175mm 230mm 280mm

U-value

Advantages

50mm PolyfoamFloorboard below slab

75mm PolyfoamFloorboard below slab

• Lowest cost solution• Slab acts as thermal store• Unrestricted insulation thickness• Traditional method utilising common materials

65mm PolyfoamFloorboard below screed

75mm PolyfoamFloorboard below screed

1) Concrete Ground Bearing Slab:a) Insulation below slab b) Insulation

above slab

2) Suspended Concrete (Beama) Insulation below screed

0.23-0.28

0.19-0.22

Page Number 10-11 10-11 12-13 14-15

4

SummaryKnauf Insulation provides products for a range of ground floor constructions, giving options that willcomply with the Building Regulations.

Building,Residential

Floors

Impro

ving Th

ermal P

erform

ance

System

• Screed is quickerdrying than solid slab

• Smooth surface finish• Reduced thermal mass

gives fast response toheating

• Insulation zone can beused to accommodateservices

• Allows construction oncontaminated and heavyinfill sites

• Reduces excavation costson sloping sites

• Creates a working platform• Smooth surface finish• Reduced thermal mass gives

fast response to heating

The U-values illustrate the performance range of each insulation system assuming P/A ratios of 0.3 to 0.6 – see key below:

0.21-0.24

0.24-0.27

0.6 typical detached house

0.3 typical mid-terraced house

0.45 typical semi-detached house

243mm 258mm 172mm 222mm

Good

Better

Best

• Fast and dry method• Utilises lightweight products• Allows construction on contaminated and heavy infill

sites• Reduces excavation costs on sloping sites• Low thermal mass gives fast response to heating• Traditional looking floor• ‘Warm’ surface layer

and block or reinforced plank):b) Insulation below chipboard

3) Suspended Timber

0.27-0.34

14-15 14-15 16-17 16-17

5


50mm (2x25mm) RocksilFloor Slab belowchipboard

75mm PolyfoamFloorboard belowchipboard

150mm Crown Loft Rollbetween timber floorjoists

200mm Crown Loft Rollbetween timber floor joists

• Fast and dry method• Creates a working platform• Allows construction on contaminated and heavy

infill sites• Reduces excavation costs on sloping sites• Low thermal mass gives fast response to heating• Traditional looking floor• ‘Warm’ surface layer

0.24-0.27

0.21-0.24

0.17-0.19

6


General

The three most important factors to consider

when insulating a ground floor are:

• What is the applied loading?

• Where is the insulation to be

positioned within the floor structure?

• What thickness of insulation will

be required to meet the Building

Regulations?

Other design considerations include

preventing condensation, minimising

air leakage and thermal bridging.

Applied Floor Loading

All materials are compressed under

load. Insulation materials used under

slabs, screeds and chipboard should be

capable of accommodating the applied

loads with the minimum of compression.

The applied load has two components:

• the dead load, which is due to the

weight of the materials laid on the

insulant, and

• the design load

BS 6399: Part 1: 1996 suggests that in

dwellings, a design load of 1.5 kN/m2

should be allowed for in all cases.

The dead loads applied by various

building components are shown in the

table. However, the designer must also

consider the dynamic loads and how

they are applied. BS 6399 is based on

the uniformly distributed load (UDL). The

strength of the floor must be sufficient to

support any applied loads over the

loaded area. For example, a large

cupboard raised on feet has a

significantly increased point loading

compared to one sat on the whole

base. The Applications section shows

the compression resistance of individual

insulants, where relevant.

Detailed Design Considerations

Suspended timber ground floors are

easily insulated

Dead loads applied by various building componentsElement Dead load (kN/m2)

Flooring grade chipboard 0.1 to 0.2

65mm concrete screed 1.50

75mm concrete screed 1.75

150mm concrete floor slab 3.50

Additional design load to BS 6399: Part 1: 1996 (dwellings) 1.50


7

Position of Insulation

The position of the insulation in a ground

floor influences the thermal mass of a

building.

Positioning the insulation under

chipboard or a screed will allow the

building to heat up quickly because the

insulation is close to the inside of the

building.

Positioning the insulation below the

slab increases the thermal mass of

the building. This results in more even

temperatures and a reduced risk of

condensation. This is best suited to

buildings that are continuously heated

or benefit from significant solar gains.

In ground level suspended timber floors

above a ventilated airspace, the

insulation is normally located between

the joists. Timber floors have little thermal

mass and are therefore best suited to

intermittent heating systems.

Floating screed on slip sheet/VCL

Insulation

Concrete slab

Damp proof membrane

Concrete slab

Insulation

Damp proof membrane

Screed

Continue wall insulation at least150mm below top of perimeterinsulation and support on a row of ties.

Continue wall insulation at least150mm below top of perimeterinsulation and support on a row of ties.

Concrete ground floor with floating screed

Concrete ground floor with insulation under slab

Alternative positions for floor insulation – concrete slabs

Chipboard/timber boarding on VCL

Insulation

Beam and block floor

Insulation between joists

Chipboard/timber boarding

Polypropylene netting

Continue wall insulation at least150mm below top of floor insulationand support on a row of ties.

Ventilated airspace

Continue wall insulation at least150mm below top of floor insulationand support on a row of ties.

Beam and block floor with floating chipboard deck

Suspended timber ground floor

Minimum 35mm mineral woolinsulation between last joist and wall

8


Building Regulation

Requirements

The table below shows the U-value

requirements in the Building Regulations

for ground floors.

U-value (W/m2K)

England, Wales and

Northern Ireland 0.25

Scotland 0.25 or 0.22

Ireland 0.25

In the various Building Regulations there

are trade off methods that allow the

performance of a particular building

element to be worse than the Elemental

U-value. This has to be compensated for

either by improving the performance in

other building elements, or the heating

system performance. There is usually a

maximum permissible U-value for each

element in the trade off methods.

Calculation of U-values

Unlike walls and roofs, the heat loss

through a ground floor varies with its

size and shape. The Building

Regulations require that when ground

floor U-values are calculated, BS EN

ISO 13370: 1998 should be used.

The British Standard uses the ratio of

the exposed floor perimeter to the floor

area to take account of the variation in

heat loss due to floor size and shape.

The measurement of the perimeter and

area should be to the finished inside

surfaces of the perimeter walls that

enclose the heated space. Projecting

bays should be included, but unheated

spaces such as porches or garages

should be excluded.

In the case of semi-detached and

terraced dwellings and blocks of flats,

the floor dimensions can either be taken

as those of the individual dwellings

themselves, or of the whole building.

When considering extensions to existing

buildings the floor dimensions may be

taken as those of the complete building

including the extension.

Determining the U-value

The charts above show the thickness of

insulation needed to achieve a U-value

of 0.25 W/m2K when insulating a

ground floor.

The charts are based on the ground

having a thermal conductivity of 1.5

W/mK. The U-values for Crown Loft Roll

assume it is placed between 50mm

wide timber floor joists spaced at

600mm centres. However, look up

tables, particularly for suspended ground

floors, only give a guide to the expected

performance. The high number of

Look up charts to achieve a U-value of 0.25 W/m2K

0.14 –0.19

0.12 –0.13

0.20 –0.229

0.30 –0.443

0.44 –1.00

up to 0.111

Polyfoam Floorboard Standardyfoam Floorboard Standard

P/Aratio

25 35 50 65 75

50

+

50

0.25 –0.339

0.19 –0.224

0.40 –0.883

0.84 –1.00

up to 0.188

Polyfoam Floorboard Standardm Floorboard Standard

P/Aratio

25 35 50 65 75

Concrete ground bearing slab Suspended concrete beam and block floor

Suspended timber floor

0.51 –1.00

0.20 –0.550

up to 0.199

Crown LoftRollCrown LoftRoll

P/A

ratio

100 150 170


9

variables that have to be taken into

account can significantly affect the U-

value for a particular set of conditions.

To calculate U-values to your own

specific requirements, Knauf Insulation

recommend the use of its Architectural

Calculation Suite (ACS) version 5.09 –

alternatively, consult the Knauf Technical

Advisory Centre who can carry out the

calculations for you.

Condensation

A vapour barrier is not normally required

for most ground floor constructions.

However, a vapour barrier should be

installed between the insulation and a

chipboard floor, especially if there is a

risk of excessive moisture from the floor

slab drying out.

Thermal Bridging

Thermal bridges are a significant source

of heat loss. They may also cause

localised condensation and mould

growth.

Correct detailing at the junction of the

floor slab and external wall, as shown

in the details on page 7, will reduce

thermal bridging and thus the risk of

condensation.

Where insulation is placed between

timber joists, the joists have the potential

to act as thermal bridges. However,

where joists are at least 150mm deep

and the space between them is fully

filled with insulation, the timber does not

constitute a thermal bridge.

Air Leakage

With suspended timber ground floors,

care is needed to minimise air leakage

from the ventilated sub floor void into

the heated space. As well as gluing the

joints between the floor deck panels, the

floor perimeter should be sealed by

applying expanded foam tape under the

skirting and a continuous bead of sealant

to the back of the skirting prior to fixing.

British Standards

Designers should consult Agrément

Certificate 93/2936 for Polyfoam

Floorboard, or BS 5669: Part 2 and BS

7916 when selecting chipboard or other

floor decking boards.

Guidance on the design and installation

of concrete bases and screeds to receive

in-situ flooring is given in BS 8204:

Part 1.

Advice on resilient floor coverings,

including recommendations for suitable

bases is given in BS 8203.

3

4

8

(10)

5

6Garage

Porch

The following worked example illustrates

how to use the charts.

Worked example

Example – a semi-detached house as

shown on the left

Perimeter P = 8+4+3+6+5 = 26m

Area A = (10x8) - (6x3) = 62m2

Ratio P/A = 26/62 = 0.42

Reading off from the charts opposite

shows that a ground floor with a P/A

ratio of 0.42 would achieve U-values of

0.25 W/m2K or better if insulated with

65mm Polyfoam Floorboard in a ground

bearing concrete slab, 75mm Polyfoam

Floorboard in a beam and block floor

or 150mm Crown Loft Roll in a

suspended timber ground floor.

Bead of sealant

Expanding foamtape compressedwhen skirting fixed

Minimising air leakage in a

suspended timber ground floor

Insulation below slab

25mm Polyfoam Floorboard Standard

Concrete ground floor slab

Damp proof membrane

Polyfoam Floorboard Standard onsand blinding

Wall insulation to extend at least150mm below floor insulation

10

Typical Construction

A solid concrete ground floor slab on a

damp proof membrane on Polyfoam

Floorboard insulation laid directly over

blinded hardcore. A strip of Polyfoam

Floorboard insulation, minimum 25mm

thick, should be placed vertically at the

slab perimeter to minimise thermal

bridging. The concrete slab may be

screeded or alternatively have a power

float finish.

The wall insulation should start a

minimum of 150mm below the top of

the floor insulation.

Installation

Level the sand blinding over the hardcore

to receive the insulation boards. Lay

Polyfoam Floorboard directly over the

sand blinding in a staggered pattern to

cover the whole floor area. The joints

should be tightly butted.

Place a strip of insulation, minimum

25mm thick, vertically at the slab

perimeter to minimise thermal bridging.

The height of the perimeter insulation to

equal the slab thickness. Ensure the

perimeter insulation boards are securely

held in place to prevent dislodgement by

following work, eg by taping them to the

main floor insulation.

Lay the damp proof membrane over the

insulation and lap with the wall dpc. Use

spreader boards, as necessary, when

placing the concrete floor to prevent

point loads puncturing the DPM.

The concrete slab may be screeded or

alternatively have a power float finish.

1a) C

oncrete G

round B

earin

g Sla

b –

Insu

latio

n b

elow

slab

2

3

4

Products

• Polyfoam Floorboard is a high

performance, 100% ozone friendly,

extruded polystyrene, rigid board

insulation. It is lightweight, yet has

excellent structural strength and long

term effectiveness. The boards are

square edged.


Floors

1

1

5

2 3

5

4

11


Performance

• Thermal performance

Polyfoam Floorboard Standard is a high

performance insulant, with a thermal

conductivity of 0.029 W/mK. Unlike

most other insulants, the effect of

moisture on performance is negligible.

The table gives U-values for a range of

perimeter/area ratios. For an

explanation of how to calculate ground

floor U-values see page 9.

• Fire performance

When Polyfoam Floorboard is installed

in a concrete floor construction, it will

not contribute to the development stages

of a fire.

• Moisture resistance

The moisture resistance of Polyfoam

Floorboard allows it to be laid exposed

to ground water, with negligible impact

on performance. The board itself does

not perform the function of a damp

proof membrane. However, it can be

laid in damp conditions or up against

wet concrete without compromising its

thermal performance.

• Compression resistance

Polyfoam Floorboard is highly resistant

to compression. It is suitable for long

term static loads of up to 40 kPa, after

allowing a factor of safety of 5; and

occasional loading of up to 66 kPa,

after allowing a factor of safety of 3.

Certification

Polyfoam Floorboard Standard is third

party certified by the British Board of

Agrément.

U-values (W/m2K) of concrete ground floor slab insulated withPolyfoam Floorboard Standard

Polyfoam U-values (W/m2K)

Floorboard Ratio of perimeter (m) to area (m2)thickness (mm) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

75 0.12 0.17 0.19 0.21 0.22 0.22 0.23 0.23

65 0.12 0.18 0.21 0.22 0.23 0.24 0.25 0.25

50 0.13 0.19 0.23 0.26 0.27 0.28 0.29 0.29

35 0.14 0.22 0.26 0.30 0.32 0.33 0.34 0.35

25 0.15 0.23 0.29 0.33 0.36 0.38 0.39 0.40

Note: The U-values have been calculated using BS EN ISO 13370: 1998 and assume a clay subsoil witha thermal conductivity of 1.5 W/mK.

Advantages

Polyfoam Floorboard

• No water absorption so can be

installed below DPM with no loss of

thermal performance

• Can be used above a DPM to protect

it during the concrete pouring process

• High compression resistance

• Resists tough site conditions

• Structural and thermal solution

Insulation above slab

Flooring grade chipboard

Vapour control layer

Polyfoam Floorboard or Rocksil Floor Slab

Concrete floor slab

Damp proof membrane


12


A solid concrete ground floor slab on a

damp proof membrane on blinded

hardcore. Polyfoam Floorboard laid over

the whole of the concrete floor slab and

finished with either a screed or flooring

grade chipboard. Alternatively, Rocksil

Floor Slab can be used below flooring

grade chipboard.

Installation

Lay the Polyfoam Floorboard Standard

or Rocksil Floor Slab directly over the

whole of the concrete floor. The surface

of the floor should be smooth and flat

to within 5mm when measured with a

3m straight edge. Irregularities greater

than this must be levelled out. Where

a beam and block floor has a camber

or uneven upper surface a levelling screed

is recommended.

Chipboard finish

Where there is a risk of moisture from

drying out of the floor slab, a vapour

control layer, such as 1000 gauge

polythene, should be used. Lay the

vapour control layer over the insulation

and turn it up at the junction with the walls.

Lay the chipboard in a staggered pattern

and glue all joints using a waterproof

PVA adhesive. Leave an expansion gap

of at least 10mm or 2mm per metre

run of floor at the room perimeter. At

doorways or access traps to pipework

runs, support the cut edges of chipboard

on preservative treated battens.

Screed finish

Place a minimum 25mm thick vertical

piece of Polyfoam Floorboard to he

full depth of the screed, around the

perimeter minimise thermal bridging.

Tape the perimeter insulation boards

1b) C

oncrete G

round B

earin

g Sla

b –

Insu

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n a

bove sla

b

2

3

4

5

Products







square edged.





Floors

1

1

6

2 3 4 56

13


Performance



performance insulant, with an aged

thermal conductivity of 0.029 W/mK.

Rocksil Floor Slab has a thermal

conductivity of 0.035 W/mK.

The table gives U-values for a range

of perimeter/area ratios. For an

explanation of how to calculate

ground floor U-values see page 8.



in a floor construction it will not

contribute to the development stages

of a fire.

Rocksil Floor Slab is classified as

Euroclass A1 to BS EN ISO 13501-1.








Certification



Agrément.

Advantages

Polyfoam Floorboard

• Compression resistant, supporting

screed under high point loads

• Provides high thermal performance

in limited insulation zone


• Resistant to site damage

• Can be used as a working platform

for following trades before screed or

chipboard is laid

• Chipboard floors do not require battens

Rocksil Slab

• Will accommodate slight imperfections

in sub floor

U-values (W/m2K) of concrete ground floor slab insulated withPolyfoam Floorboard Standard below a screed or chipboard



75 0.12 0.17 0.19 0.21 0.22 0.22 0.23 0.23

65 0.12 0.18 0.21 0.22 0.23 0.24 0.25 0.25

50 0.13 0.19 0.23 0.26 0.27 0.28 0.29 0.29

35 0.14 0.22 0.26 0.30 0.32 0.33 0.34 0.35

25 0.15 0.23 0.29 0.33 0.36 0.38 0.39 0.40


U-values (W/m2K) of concrete ground floor slab insulated withRocksil Floor Slab below chipboard

Rocksil U-values (W/m2K)

Floor Slab Ratio of perimeter (m) to area (m2)thickness (mm) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

2x25 0.14 0.21 0.25 0.28 0.30 0.31 0.31 0.32


securely in place to prevent

dislodgement by following work.

Cover the Polyfoam Floorboard with a

separating slip layer and turn up at the

junction with the walls. If the project is a

refurbishment job and secondary damp

proofing is required use a suitable DPM

that will also act as a slip layer.

Lay a minimum 65mm thick reinforced

sand/cement screed. The screed should

be reinforced to BS 8204: Part 1:2003.

This can be either through the use of

light steel mesh at half screed depth

or the addition of polypropylene

reinforcing fibres in the screed mix.

It is important to compact the screed

well to produce a durable floor surface.

Polyfoam Floorboard is suitable for use

with thinner, non-standard thickness

liquid screeds based on specification

advice from the screed supplier.

Suspended concrete floor

Screed or chipboard

Isolating membrane

Polyfoam Floorboard or Rocksil Floor Slab

Suspended concrete floor

Ventilated sub floor

25mm Polyfoam Floorboard Standard


14


A concrete beam and block floor

overlaid with Polyfoam Floorboard and

finished with either flooring grade

chipboard or a sand/cement screed.

Polyfoam Floorboard is also suitable for

use with thinner, non-standard thickness

liquid screeds based on specification

advice from the screed supplier.

Where a screed is used, a strip of

Polyfoam Floorboard insulation, minimum

25mm thick, should be placed vertically

at the perimeter of the screed to minimise

thermal bridging. A slip layer of 1000

gauge polythene sheet should be placed

between the insulation and the screed.

The wall insulation should start a minimum

of 150mm below the top of the floor

perimeter insulation.

Installation

Polyfoam Floorboards can be used on a

beam and block suspended concrete

floor that is the subject of a current BBA

Certificate and installed in accordance

with, and within the limitations imposed

by that Certificate. The surface of any

floor should be smooth and flat to within

5mm when measured with a 3m straight

edge. Provided the surface is smooth

and level, the insulation may be laid

directly onto the flooring system.

Otherwise lay a thin levelling screed (this

may be the grout with beam and block

systems) prior to laying the insulation.

Irregularities greater than those detailed

above must be removed.

Where a beam and block floor has a

camber or uneven upper surface a

levelling screed is recommended.

2)

Susp

ended

Concrete Flo

or

2

3

4

5

Products







square edged.





Floors

1

5

7

6

16

7

2 3 4

15


Screeded finish

Place a minimum 25mm thick vertical

piece of Polyfoam Floorboard, to the

full depth of the screed, around the

perimeter to minimise thermal bridging.

Ensure these perimeter insulation boards

are securely held in place to prevent

dislodgement by following work.

Lay the slip layer over the insulation and

turn up at the junction with the walls.

Lay a minimum 65mm thick reinforced

sand/cement screed. The screed should

be reinforced to BS 8204: Part 1 :

2003. This can be either through the

use of light steel mesh at half screed

depth or the addition of polypropylene

reinforcing fibres to the screed mix.

It is important to compact the screed

well to produce a durable floor surface.

Chipboard finish

The insulation should be laid over the

whole of the beam and block floor.

Lay the chipboard in a staggered pattern

with all joints glued using a waterproof

PVA adhesive. Leave an expansion gap

of at least 10mm or 2mm per metre

run of floor at the room perimeter. At

doorways or access traps to pipework

runs support the cut edges of chipboard

on preservative treated battens. If in

doubt refer to the board manufacturer’s

instructions.

Performance



performance insulant, with a thermal


Rocksil Floor Slab has a thermal


The table gives U-values for a range

of perimeter/area ratios. For an


floor U-values see page 8.



in a floor construction it will not contribute

to the development stages of a fire.

Rocksil Floor Slab is classified as

Euroclass A1 to BS EN ISO 13501-1.








Certification



Agrément.

U-values (W/m2K) of beam and block ground floor insulated withPolyfoam Floorboard Standard



25+65 0.15 0.19 0.21 0.22 0.23 0.24 0.24 0.24

75 0.17 0.21 0.24 0.25 0.26 0.27 0.28 0.28

65 0.18 0.23 0.25 0.27 0.29 0.30 0.30 0.31

50 0.19 0.26 0.30 0.32 0.34 0.35 0.36 0.37

35 0.22 0.30 0.35 0.38 0.41 0.43 0.44 0.46

25 0.23 0.33 0.40 0.44 0.48 0.50 0.52 0.54

Note: The U-values have been calculated using BS EN ISO 13370: 1998 and assume a dense infill blockbetween concrete beams.

Advantages

Polyfoam Floorboard

• Compression resistant, supporting

screed under high point loads

• Provides high thermal performance

in limited insulation zone


• Resistant to site damage

• Can be used as a working platform

for following trades before screed or

chipboard is laid

• Chipboard floors do not require battens

Rocksil Slab

• Will accommodate slight imperfections

in sub floor

U-values (W/m2K) of beam and block ground floor insulated withRocksil Floor Slab below chipboard

Rocksil U-values (W/m2K)

Floor Slab Ratio of perimeter (m) to area (m2)thickness (mm) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

2x25 0.17 0.22 0.27 0.30 0.32 0.34 0.35 0.36

Note: The U-values have been calculated using BS EN ISO 13370: 1998 and assume a dense infill blockbetween concrete beams.

Suspended timber floor

Draughtstrip

Crown Loft Roll

Floor deck

Crown Loft Roll

Support netting

Ventilated sub-floor


16


A suspended and ventilated timber

ground floor. The insulation is laid

between the joists and supported on

polypropylene netting.

The netting should be positioned to

support the insulation so that there is no

gap between the insulation and the

underside of the floor deck.

The floor joists running parallel with

masonry walls should be spaced at least

35mm away from the wall to allow

insulation to be placed next to the wall.

To minimise air leakage at the floor

perimeter, the skirting board should have

a self-adhesive strip of expanding foam

applied to its lower edge and a

continuous bead of sealant applied

to its back surface before fixing.

The wall insulation should start a minimum

of 150mm below the top of the floor

insulation.

Installation

If the insulation is the full depth of the

floor joists, staple the support netting to

the underside of the first joist and unroll

the netting, stapling to the underside of

each joist as the netting is unrolled.

Where the joist is deeper than the floor

insulation, mark the depth of the

insulation on the side of the joists. Staple

the support netting along this line and

pull taut to the adjacent joist and staple

again. Pull the netting over the top of the

joist and staple to the depth of the floor

insulation. Repeat the process until there

is netting support to the whole floor.

Unroll the Crown Loft Roll to completely

fill the space between the joists. There

3) Su

spen

ded

Timber Flo

or

2

3

4

5

Product

• Crown Loft Roll is made from glass

mineral wool and formed into

unfaced rolls which are lightweight,

flexible, resilient and non-combustible


Floors

1

1

4 53 6

7

2

6

7

17


Performance


Crown Loft Roll has a thermal


The table gives U-values for a range of

perimeter/area ratios. For an


floor U-values, see page 8.


Crown Loft Roll is classified as Euroclass

A1 to BS EN ISO 13501-1.

U-values (W/m2K) of suspended timber ground floor insulated with Crown Loft Roll

Crown Loft Roll U-values (W/m2K)

thickness Ratio of perimeter (m) to area (m2)(mm) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

200 0.13 0.16 0.17 0.18 0.19 0.19 0.19 0.20

170 0.14 0.18 0.19 0.20 0.21 0.22 0.22 0.22

150 0.15 0.19 0.21 0.22 0.23 0.24 0.24 0.24

100 0.18 0.23 0.26 0.28 0.30 0.31 0.32 0.32

Notes: The U-values have been calculated using BS EN ISO 13370: 1998 and assume 48mm widejoists at 600mm centres.

should be no air gap between the

insulation and the underside of the floor

deck. Joists running parallel with

masonry walls should be spaced away

from the wall to allow no less than

35mm of insulation to be placed next to

the wall.

Lay the chipboard floor deck in the

usual way, using waterproof PVA glue at

the joints, and allow a minimum 10mm

gap at the room perimeter.

When fixing the skirting board, apply a

self-adhesive foam strip to the underside

of the skirting and two beads of sealant

to the back surface. Apply pressure to

ensure the foam strip is compressed

immediately before fixing the skirting

in place.

Advantages

• Crown Loft Roll is manufactured to suit

standard joist spacings, so no cutting

is required

• Insulation friction fitted between joists,

with tight fit against timber

• Non-combustible product

• Low embodied energy and

environmentally friendly


18

1) Ground bearing slab

1a) Insulation under slab

The whole of the ground floor area

between brick, block or concrete

subwalls to be insulated with Polyfoam

Floorboard Standard …...mm thick and

laid directly over blinded hardcore.

Polyfoam Floorboard, at least 25mm

thick, to be cut and placed vertically

against the subwalls to the depth of the

concrete slab.

The insulation to be laid above*/below*

damp proof membrane, which should

lap the perimeter wall dpc. Concrete

slab and floor finish as specified by

the designer. (*delete as required)

Alternatively, refer to NBS clause:

E20/30 or E20/200

1b) Insulation above slab and

below screed

Polyfoam Floorboard Standard ......mm

thick, to be closely butted and placed

over the whole area of the floor.


thick, to be cut and placed to full depth

of screed at the floor perimeter.

The insulation to be overlaid with 1200

gauge polythene, taken up and over the

perimeter insulation. A 65mm thick

sand/cement screed with wire mesh*/

polypropylene reinforcing fibres* to be

laid on top. (NHBC recommend a D49

fabric mesh for use in floating screeds.)

Floor finish as specified by the designer.

(* delete as appropriate)

Typical Specification ClausesAlternatively, refer to NBS clause:

M10/40 or M10/290

1b) Insulation above slab and

below chipboard

The whole area of the concrete floor to

be lined with Polyfoam Floorboard

Standard, …...mm thick. All boards to

be close butted.

The insulation to be (overlaid with a

vapour control layer of 1000g

polythene and)* covered with 18mm

t&g flooring grade chipboard. (*delete

as required)


K11/25 or K11/225

2) Suspended masonry floor

2a) Insulation below screed

Polyfoam Floorboard Standard ......mm

thick, to be closely butted and placed

over the whole area of the floor.


thick, to be cut and placed to full depth

of screed at the floor perimeter.

The insulation to be overlaid with 1200

gauge polythene, taken up and over the

perimeter insulation. A 65mm thick

sand/cement screed with wire mesh*/

polypropylene reinforcing fibres* to be

laid on top. (NHBC recommend a D49

fabric mesh for use in floating screeds.)

Floor finish as specified by the designer.

(* delete as appropriate)


M10/40 or M10/290

2b) Insulation below chipboard

The whole area of the concrete floor to

be lined with Polyfoam Floorboard

Standard, …...mm thick. All boards to

be close butted.

The insulation to be (overlaid with a

vapour control layer of 1000g polythene

and)* covered with 18mm t&g flooring

grade chipboard. (*delete as required)


K11/25 or K11/225

3) Timber suspended floor

Polypropylene netting to be (draped over

and between the joists and stapled to

the sides of each joist*/stapled to the

underside of the joists*). (*delete as

required)

Crown Loft Roll of ......mm thickness and

of width to suit joist spacings, supported

on the netting to fit tightly under the floor.

Crown Loft Roll to be cut and placed to

fully fill in the gap between the last joist

and the perimeter wall. T&g flooring

grade chipboard to be nailed or

screwed to the floor joists, all as

specified by the designer.


P10/240 or P10/250


19

Residential

Pitched Roofs External Walls Internal Walls Floors

Upper Floors(N&C)Solutions for insulatingexposed aboveground floors inboth timber andconcreteconstruction

Ground Floor(N)Solutions forinsulating bothslab on andsuspendedground floors in both concreteand timberconstruction

Basement Walls

Masonry Solid(N&C)Solutions forexternal basementwall to preventthermal transitionto the earth

Partition Walls(N&C)Solutions fordividing internalrooms in singledwellingconstruction

SeparatingWalls (N&C)Solutions for highperformanceseparating wallsbetween separate,but attacheddwellings

New Build andUpgrade (N)Solutions for new build "room in roof",warm roof andceiling level coldroof insulation andupgrading existingcold roof insulation

Loft Conversion -Room in Roof (C)Solutions forconverting existingattic space into living area

Masonry Cavity(N&C)Solutions formasonry cavity wallconstructionfull and part fill

Timber Frame (N)Solutions forinsulation inmodern timberframe homes

Masonry Solid (N&C)Solutions forinternal andexternal insulationapplied to solidmasonry walls

B/R/PR/1 B/R/XW/1 B/R/IW/1 B/R/BW/1 B/R/F/1

B/R/F/2

Separating andInternal Floors(N&C)Acousticsolutions forfloors separatingtwo dwellingsand floors withina single dwelling

B/R/F/3

B/R/IW/2

B/R/PR/2

B/R/XW/2

B/R/XW/3

Detached Homes Semi Detached Homes Terraced Homes Apartments

Building & Construction

N= New Build C= Conversion

Legend

B/NR/CS/1

Each green “box” referencemeans that a dedicatedbrochure is available on this application

Mar 2004This information booklet is complemented

by comprehensive specification and

application system recommendations

in the Knauf Insulation Guide, available

through visiting our website.

Customer Service (Sales)

Freephone 0800 627465

Fax: 01744 612007

E-mail: [email protected]

Insulation Academy Technical

Advisory Centre

Tel: 01744 693885

Fax: 01744 693882


Literature

Tel: 01270 824024

Fax: 01270 824025


Website

www.knaufinsulation.co.uk (UK)

www.knaufinsulation.ie (Ireland)

Knauf Insulation Ltd

PO Box 10

Stafford Rd

St Helens

Merseyside

WA10 3NS

B/R/F/1

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