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- 1. Octagonal Roof
- 2. Draw Crown Rafters Walls are parallel Set Back ½ Rafter Thickness
- 3. Draw & Bisect Crown End Rafter
- 4. Draw Tangents to the Crown Ends
- 5. Draw Top Plate
- 6. Clean Up Drawing
- 7. Clean Up Drawing Angle Between Major Crown End & Centring Rafters = 90 ⁰
- 8. Clean Up Drawing Angle Between Crown End Rafters = 45 ⁰
- 9. Clean Up Drawing Angle Between Crowns Ends & Hips = 22.5 ⁰
- 10. Angles formed by the Roof These angles are the same no matter the size of Roof as it is a Geometric Shape
- 11. Length Of Octagonal Ends If the angle between the members is constant 22.5 ⁰ We can say in all cases, no matter the size of the roof ½ End = ½ Span x tan 22.5⁰ = ½ Span x 0.414 (tan 22.5⁰ is always used)
- 12. If the angle between the members is constant 22.5 ⁰ We can say in all cases, no matter the size of the roof ½ End = ½ Span x 0.414 Length Of Octagonal Ends
- 13. Length Of Octagonal Ends If the angle between the members is constant 22.5 ⁰ In all cases, we can say Full End = ½ Span x 0.414 x 2
- 14. Length Of Octagonal Ends If the angle between the members is constant 22.5 ⁰ Also in all cases, the full end will be Full End = ½ Span x 0.828
- 15. Length Of Octagonal Ends These formulas are the same no matter the size of the Roof ½ End = ½ Span x 0.414 Full End = ½ Span x 0.828
- 16. Major Crown End Rafter These formulas are the same no matter the size of the Roof Calculating Centring rafters and Crown End Rafter use the same method as a normal hip roof
- 17. Major Crown End Rafter These formulas are the same no matter the size of the Roof Calculating Centring rafters and Crown End Rafter use the same method as a normal hip roof
- 18. Minor Crown End Rafters These formulas are the same no matter the size of the Roof Minor Crown End Rafters join in a similar manner to a hip rafter
- 19. Minor Crown End Rafters These formulas are the same no matter the size of the Roof Minor Crown End Rafters join in a similar manner to a hip rafter The Plan run of the minor crown is reduced by ; ½ Centring Rafter x 1.414
- 20. Minor Crown End Rafters These formulas are the same no matter the size of the Roof Minor Crown End Rafters join in a similar manner to a hip rafter Minor Crown = ½ Span x ½ C.R Thickness÷
- 21. Edge Bevel Minor Crown End Rafters Plan Angle = 45 ⁰
- 22. Edge Bevel Minor Crown End Rafters Plan Angle Plan Angle = 45 ⁰ Plan Angle = 90 ⁰
- 23. Edge Bevel Minor Crown End Rafters Plan Angle Plan Angle = 45 ⁰ Plan Angle = 90 ⁰ Both Sides Must Be Equal
- 24. Edge Bevel Minor Crown End Rafters Plan Angle Plan Angle = 45 ⁰ Plan Angle = 90 ⁰ Both Sides Must Be Equal When Can You Use The Plan For the Edge Bevel ?
- 25. Edge Bevel Minor Crown End Rafters True Angle

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