Roof Designs & Construction

Calculating a Roof Pitch

Architecture I

What is the Roof Pitch?

The roof's Pitch is what is called "slope" in geometry

Pitch = Rise/Run Run = ½ Span

Roof Pitch to Degree Equivalents

This drawing demonstrates how many degrees rise for each pitch of a typical roof. Look at the column labeled pitch, then look under degrees to get the corresponding amount of degrees.

Example;

8/12 pitch = 33.75 degrees.

Common

Roof Pitches

Various Roof Pitches

The roof pitch is defined in ranges which can reasonably be determine from field observation without precise measurement.

o Very Low or Flat Roofs are < 1 in 12 pitch

o Low Pitched Roofs are < 4 in 12 pitch

o Medium Pitched Roofs are < 9 in 12 pitch

o Steep Roofs are < 12 in 12 pitch

o Very Steep Roofs are > 12 in 12 pitch

Roof Plan

Sketch the Front Elevation

Roof Pitch & Roof Plan Problem

Calculate the roof pitch and sketch the roof plan for the following house:

2 STORY HOUSE 2 CAR GARAGE

48’-0”

32’

-0”

24’-0”

2

2’-0

”

Roof Framing Systems

Architecture IFairport High School

Roof Members

Conventional Framed Roof

Wood Trussed Roof

Carpenter Truss Components

Trussed Rafter Components

Trussed Gambrel Components

Flat Roof Truss Components

Truss Types

Cornice Framing Details

Drawing a Cornice Section

Roof Plan

Detailed Roof Framing Plan

Roof Framing Plan Detail

Rafter SpansMaximum Span Size

Rafter Spacing Rafter Group 1 Group 2 Group 3 Group 4

12” 10’-0” 9’-0” 7’-0” 4’-0”

16” 9’-0” 7’-6” 6’-0” 3’-6”

24” 7’-6” 6’-6” 5’-0” 3’-0”

2 x 4

32" 6’-6” 5’-6” 4’-0” 2’-6”

12” 17’-6” 15’-0” 12’-6” 9’-0”

16” 15’-6” 13’-0” 11’-0” 8’-0”

24” 12’-6” 11’-0” 9’-0” 6’-6”

2 x 6

32" 11’-0” 9’6” 8’-0” 5’-6”

12” 23’-0” 20’-0” 17’-0” 13’-0”

16” 20’-0” 18’-0” 15’-0” 11’-6”

24” 17’-0” 15’-0” 12’-6” 9’-6”

2 x 8

32" 14’-6” 13’-0” 11’-0” 8’-6”

12” 28’-6” 26’-6” 22’-0” 17’-6”

16” 25’-6” 23’-6” 19’6” 15’-6”

24” 21’-0” 19’-6” 16’-0” 12’-6”

2 x 10

32" 18’-6” 17’-0” 14’-0” 11’-0”

Wood Ceiling Joist Spans

Maximum Span Size Ceiling J oists

Spacing Ceiling J oists

Wood Group 1

Wood Group 2

Wood Group 3

Wood Group 4

12” 11’-6” 11’-0” 9’-6” 5’-6” 2 x 4 16” 10’-6” 10’-0” 8’-6” 5’-0”

12” 18’-0” 16’-6” 15’-6” 12’-6” 2 x 6 16” 16’-0” 15’-0” 14’-6” 11’-0”

12” 24’-0” 22’-6” 21’-0” 19’-0” 2 x 8 16” 21’-6” 20’-6” 19’-0” 16’-6”