Octagon Rafter Calculator

Strong Built Establishments Builders

SBE Builders is a commercial and residential framing contractor located in Discovery Bay California. Our Systematic Construction Logic produces Strong Built Establishments. E-Defense stands for Earthquake-Defense.

Octagon Rafter Calculator v1.0

F	Feet		Inches

	Common Rafter Overhang

	Jack Rafter O.C. Spacing

P	Common Rafter Pitch

show results in feet & inches

results are show below in the IFrame window

All online tools use javascript to calculate the dimensions. Use at your own risk. If the answers look wrong then verify the answers with a calculator.

This octagon rafter script - calculator will return the octagon rafter geometry angles and trigonometry rafter measurements for equal sided octagon roof framing.

In a circle of radius r, the length of the chord that subtends a central angle x is r * sin( x/2).
This script uses the theory of an octagon inscribed inside of a circle. So the radius is the run of the octagon hips and the chord is the length of the sides of the octagon.

full-octagon.dxf -- auto generated DXF CAD file of octagon rafters drawing each time script is run
full-octagon.pl source code for perl script that generates these octagon rafter calculations
dxf_header.txt DXF header text file used by this script

SBE Builders
5305 Laguna Ct.
Discovery Bay, California 94505
(925) 634-6022 • Fax: (925) 634-6022

Commercial & Residential Framing Contractor
Build it Green Framing Contractor
American Carpenter and Builder
California Licensed General Building Contractor
CA LIC.# 546126
Expert Witness for Construction Structural defects

Roof Framing Geometry

Roof framing geometry is empirical-type knowledge.
Information gained by means of observation, experience, or experiment.
From ground Line 0: Z1, Z2, Z3 etc...
To Roof Axis 0: A1, A2, A3 etc...
To the bring back line 0 for scribing: B1, B2, B3 etc...

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