Wall Hip Rafter Run

Projection Wall Angle

Projection Offset

Common Rafter Run

Bay Hip Rafter  Run

Back Wall Length

Face Wall Length

Projection

of

Bay Window

Exterior Wall Angle

Interior

Wall Angle

B

Interior Wall Angle  divided  by  2 =  Bay Hip Rafter Run Bisect Angle

Bay Window Geometry

Projection Wall

A

C

c

b

a

Common Rafter Run

Bay Hip Rafter Run

Bay Hip Rafter Run Bisect Angle

                      ( BHRR)

Right Triangle

Geometry

Common Rafter Rise                =    Common Rafter Run *  tan ( Rafter Pitch Angle)

Common Rafter Length          =    Common Rafter Run ÷  cos ( Rafter Pitch Angle)

Projection Offset                        =   (Back Wall - Face Wall) /2

Projection Wall Angle                     =    arctan ( Common Rafter Run  ÷  Projection Offset )

Interior Wall Angle                   =    ( 90° - Projection Wall Angle) + 90°

BHRR Bisect Angle                     =    Interior Wall Angle  ÷  2         

Bay Hip Rafter Run                    =   Common Rafter Run ÷  sin ( BHRR Bisect Angle)

Bay Hip Rafter Angle                 =   arctan ( Common Rafter Rise ÷ Bay Hip Rafter Run)

Bay Hip Rafter Bevel Angle            =    90° - BHRR Bisect Angle               

Bay Hip Rafter Length              =   Bay Hip Rafter Run  ÷  cos ( Bay Hip Rafter Angle)

Bay Hip Rafter Run Offset       =   Common Rafter Run ÷  tan ( BHRR Bisect Angle)

Projection Offset                        =   (Back Wall - Face Wall) /2

Wall Hip Rafter Run                  =   Projection Offset + Bay Hip Rafter Run Offset

Wall Hip Rafter Angle                =   arctan ( Common Rafter Rise ÷ Wall Hip Rafter Run)

Wall Hip Rafter Length             =   Wall Hip Rafter Run  ÷  cos ( Wall Hip Rafter Angle)

Wall Hip Rafter Bevel Angle        =   Projection Wall Angle

Projection Wall Length             =   Projection Offset ÷  cos ( Projection Wall Angle)

Bay Hip Rafter Run Offset

                     

EQUAL PITCH BAY WINDOW RAFTER FRAMING CHEAT SHEET