Roof Connection Details

Eave & Rake Details

Definition: Architectural details that incorporates the roof to the wall assembly

Common members included in details:– fascia and fascia trim– soffit and soffit vents– lookout or outrigger– slope/pitch– rafter and ceiling joist– double top plate

Terms to Know--Rake Detail

Definition: Detail taken at the sloped edge of roof or at the gable end of the building, usually this detail is perpendicular to Eave Details

Terms to Know--Fascia Finished member secured to end of rafters Some construction include a sub-fascia in

preparation to receiving a finished fascia.

Terms to Know--Soffit Enclosed/boxed-in area or open area below

rafters on the overhang of a roof

Soffit Area

Terms to Know--Eave Detail

The projecting portion of the roof parallel to the slope. Sometimes called the cornice detail

To draw eave detail, architect needs to know– roof material--wood vs. composition shingles– rafter size & spacing– roof/eave overhang– roof slope/pitch– roof sheathing– exterior wall sheathing– eave design

Eave Detail

Roof Pitch

Pitch– Rise over Span– Always reduced to the smallest fraction

Roof Slope Slope

– Slope is stated as a ratio of rise over run with run, run is 1/2 of span but is always expressed as a base of 12

– Slope is placed on a detail as a upside down triangle with 12 (run) horizontal line and rise by the vertical line

Drafting Slope in a Detail Assume the slope is 6:12 as shown below All is necessary is to determine hypotenuse of a triangle

having a base of 12 units and the leg of 6 units Draft a line 12” long using the scale of your drawing Then a vertical line 6” long with the same scale The diagonal is the slope for this problem

12” BASE LINE

6” L

EG

LIN

E

SLOPE LINE fo

r

DETAILING

Calculations for Slope Problem: Span of a building is

30’, Rise is 5’, what is the slope?

Run = 1/2 Span = .5 x 30 = 15

Slope = Rise/Run = 5/15 = x/12 (Convert) 15x = 5x12

x(new rise) = (5x12)/15 x(new rise) = 4 SLOPE =

4:12

Eave Designs

1) Exposed Tail Rafters An exposed wood member that is spliced to the

common rafters Usually thicker than common rafter with the

spacing further apart

Boxed Cornice--Soffit Styles

1) Boxed Horizontal 2) Boxed Parallel to rafter, sloped 3) Either styles can be Open or Enclosed

2) Boxed (Enclosed) verses Open Soffit

Boxed Horizontal or Boxed Parallel to rafter and sloped Open Soffit

Boxed Horizontal Soffit

Slopped Open Soffit

Soffit Design Considerations

1) Must make provision for ventilation– eave soffit (intake) and attic (exhaust)

2) Determine area of ventilation– Attic area (x) 1/150 = total area of ventilation req’d (net free area)

3) Determine location of ventilation– eaves-- soffit contiuous vs. soffit cutout – gable ends--square, rectangle, round or triangle shape– ridge --continuous along roof ridge– roof --various types projecting out of the roof

Ventilation Products/Suppliers

Ventilation Types:1) Roof Louvers

2) Gable Louvers

3) Ridgeline Vents

4) Gravity Turbines

5) Power Vents

3) Fascia Styles and Designs

vertical vs perpendicular

Fascia perpendicular to rafter

Fascia vertical to rafter

Drafting the Eave Detail

It is recommended to complete the eave detail design before drafting other roof details

Common eave/cornice detail scale sizes:

Rake Detail Rake - assembly

along sloping edge of roof

Usually different overhang from eave

No need to “notch” for rafters

Detail Example Eave Detail Notes Scale: 1 1/2” = 1’-0”

5-Ply built-up roof w/ 50# building felt@ edge

3/4” CDX plywood 5/8” GB (Interior finish) 38R fiberglass batt

insulation(12”)(ceiling) 2x8 CLG Joist @24”OC

Pre-fab trusses optional 1x6 T&G siding over

1/2” OSB 15# felt between(Match previous

details) Add 1x3 trim at fascia Full fiberglass batt

insulation in wall

Detail Notes ContinuedScale: 1 1/2” = 1’-0”

Attic insulation R38- 12” foil faced fiberglass batt 2x8 rafter and ceiling joist @ 24” OC (or prefab wd

truss) 1/2” AC exterior plywood soffit 7/8” stucco exterior finish w/ 1x2 redwood ground at top

next to soffit 24” overhang (from stucco to fascia) 2x4 lookout @ 24” OC R11-3 1/2” craft faced fiberglass batt in (2x4 studs @

16” OC