Gambrel Roof Framing Geometry Calculator - Inch
This Gambrel Roof fits in a semicircle, and starts as the top half of an equal sided octagon.
Move slider or directly enter angle to alter sweep angle of lower rafters and change the shape.
to calculate rafter overhang equal to the lower level cut at the full rafter depth.
With overhang selected, drag slider to increment - decrement birdsmouth seat width to suit.
Geometric calculator only. Check local building regulations for sizes, spans angles etc.
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