Roof DesignRoof Design

Topics of DiscussionsTopics of Discussions

• Roof types

• Roof construction terms

• Slope vs. Pitch

• Roof terminology

• Metal framing connectors

• Roof ventilation

Basic ShapesBasic Shapes

• Gable Roof

• Hip Roof

• Flat Roof

• Shed Roof

• Gambrel Roof

• Mansard Roof

• A-Frame Roof

Basic ShapeBasic Shape

• Gable Roof– Slopes in

from two sides

– Gable ends allow for attic venting

Basic ShapeBasic Shape

• Hip Roof– Slopes in

from all four sides

– No gable ends for vent attic

Basic ShapeBasic Shape

• Flat Roof– Requires a

built-up roof

– Slight slope of 1/4” to 12” helps drainage

–

Basic ShapeBasic Shape

• Shed Roof– 3/12 or more

slope– Can be shingled– Economical like

flat roof

Basic ShapeBasic Shape

• Gambrel Roof

– Two slopes from two sides

– Traditional “Barn” shape

– 2nd story under roof

Basic ShapeBasic Shape

• Mansard Roof– Two slopes

from two sides– Top nearly flat– 2nd story

within the roof area

Basic ShapeBasic Shape

• A-frame Roof– Steep for snow

country– Roof and ceiling

same structure

Roof ConstructionRoof Construction

• Basic terms:– slope/pitch--incline of roof

– roof member terms--structure of roof

– eave/cornice--detail showing wall to roof const

– fascia--visible member attached to end of rafters

– ridge--top of roof

– sheathing--material covering the top of rafters

– rafter/ceiling joist--structure framing of roof

– soffit--underneath side of roof overhang

– vents--in soffit, allows air circulation in attic

Slope Vs. PitchSlope Vs. Pitch

• Slope = Rise/Run– expressed as a ratio– always a base of 12– placed on dwg. 12

4

Slope symbol

Text book error (noted as pitch symbol)

•Pitch = Rise/Span• expressed as fraction• reduce to smallest

fraction• not placed on drawing, helpful to carpenter

Roof TermsRoof Terms

• Span– Distance across the building

Roof TermsRoof Terms

• Run– 1/2 the distance across the building (1/2 span

distance)

Roof TermsRoof Terms

• Rise– The distance the roof rises (distance from the

square of house to ridge)

Roof TermsRoof Terms

• Pitch– The fraction of the rise over span

Roof TermsRoof Terms

• Slope– Slope is stated as a ratio of rise over run with

run always as 12

Slope vs Pitch vs AngleSlope vs Pitch vs Angle

• Slope Pitch Angle

• 3:12 1/8 14°0’0”

• 4:12 1/6 18°30’

• 5:12 5/24 22°30’

• 6:12 1/4 26°30’

Roof Member TerminologyRoof Member Terminology

Metal Framing ConnectorsMetal Framing Connectors

•Keeps structural members from separating