Clipped Hip Rafter Octagon Roof Framing


The Clipped Hip Rafter Octagon Roof Framing calculator will calculate the rafter lengths for the Clipped Hip Rafter Octagon Rafters.


Input variables

  1. Roof Pitch or Angle
  2. Main Common Rafter Run
  3. Overhang Run
  4. Jack Rafter Spacing
  5. Hip Rafter Width
  6. Hip Rafter Depth
  7. Rafter Width
  8. Rafter Depth
  9. Seat Cut Level Cut Length
  10. Clipped Wall Run

Roof Pitch or Angle
Select the input type from the input menu, Imperial/English Inch base 12 —— default, enter roof pitches from 1—24 like 8 for an 8:12 pitched roof, Metric 300mm base, enter millimeters like 200 for a 33.69007° roof pitch angle, Decimal Inch base 10 —— enter base 10 decimal numbers like 5.7735 for a 30° roof pitch angle, Degrees input —— use any roof angle in degrees like 33.69007°

    Length/Dimensions Input Menu Mode
  1. Imperial/English Inch base 12 —— default.. use American standard pitches over 12.
  2. Metric 300mm base —— 300mm is 11.81102 inches, similar usage to the American framing squares printed in inches.
  3. Decimal Inch base 10 —— use this option when working with tangents or using the Chappell Master Framing Square multiply the tangent of the angle by 10

The output mode selection can be completely different from the input mode

    Length/Dimensions Output Menu Mode
  1. Imperial/English Inch base 12 —— default.. use American standard pitches over 12.
  2. Metric 300mm base —— 300mm is 11.81102 inches, similar usage to the American framing squares.
  3. Decimal Inch base 10 —— use this option when working with tangents or using the Chappell Master Framing Square

Input Length
This menu option allows you to set the main hip rafter run length for calculating the angles and dimensions of the roof.

Overhang Run
This menu option allows you to set the rafter overhang run. The rafter overhang run will be used to calculate the common rafter overhang length.

Jack Rafter Spacing
This menu option allows you to set the jack rafter On Center spacing of the jack rafters. The calculator will retun the jack rafter length difference for the main hip rafter and the valley rafter jack rafters.

Hip Rafter Width
This menu option allows you to set the width of the hip rafter. The width of the hip rafter is used to calculate the size of the king post.

Hip Rafter Material Depth , Main Material Depth
This menu option allows you to set the depth of the rafters that is used to calculate:

Rafter Material Width
Enter the rafter material width that will be used for the roof. Not really used at this time.

Rafter Material Depth
Enter the rafter material depth that will be used to determine the HAP of the rafters.

Seactcut Length
Enter a rafter seatcut length that will be used to determine the height of the heel cut (HAP).

The Clipped Hip Rafter Eave Angle will always be 135.00° for an clipped hip rafter. The Octagon Miter Angle is 22.50°. The Clipped Hip Rafter Plan Angle is 67.50°.
The Main Hip Rafter Eave Angle is 90°. The Main Hip Rafter Plan Angle is 45°. The Main Hip Rafter Pitch is the common rafter pitch over 17(16.97) in, like 8in/17in for an 8in/12in roof pitch.
The Clipped Hip Rafter Pitch is the common rafter pitch over 13(12.98871) in, like 8in/13in for an 8in/12in roof pitch.

This calculator will also calculate the main hip rafter post heigh. You can use this post height to support the main hip rafter at the pitch break between the main hip rafter and the clipped hip king common rafter.