Octagonal Roof
Draw Crown Rafters Set Back ½ Rafter Thickness Walls are parallel
Draw & Bisect Crown End Rafter
Draw Tangents to the Crown Ends
Draw Top Plate
Clean Up Drawing
Clean Up Drawing Angle Between Major Crown End & Centring Rafters = 90⁰
Clean Up Drawing Angle Between Crown End Rafters = 45⁰
Clean Up Drawing Angle Between Crowns Ends & Hips = 22.5⁰
Angles formed by the Roof These angles are the same no matter the size of Roof as it is a Geometric Shape
Length Of Octagonal Ends If the angle between the members is constant 22.5⁰ 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)
Length Of Octagonal Ends If the angle between the members is constant 22.5⁰ We can say in all cases, no matter the size of the roof ½ End = ½ Span x 0.414
Length Of Octagonal Ends If the angle between the members is constant 22.5⁰ In all cases, we can say Full End = ½ Span x 0.414 x 2
Length Of Octagonal Ends If the angle between the members is constant 22.5⁰ Also in all cases, the full end will be Full End = ½ Span x 0.828
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
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
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
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 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
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÷
Edge Bevel Minor Crown End Rafters Plan Angle = 45⁰
Edge Bevel Minor Crown End Rafters Plan Angle
Edge Bevel Minor Crown End Rafters Plan Angle Both Sides Must Be Equal Plan Angle = 45⁰ Plan Angle = 90⁰
Edge Bevel Minor Crown End Rafters Plan Angle Both Sides Must Be Equal Plan Angle = 45⁰ Plan Angle = 90⁰ When Can You Use The Plan For the Edge Bevel ?
Edge Bevel Minor Crown End Rafters True Angle