How To Figure Gambrel Roof Angles

To calculate a gambrel roof select gambrel roof from the roof type dropdown list or click on the appropriate toolbar button to calculate a gambrel roof.

How to figure gambrel roof angles.

With overhang selected drag slider to increment decrement birdsmouth seat width to suit. You will need to make 22 5 degree angle cuts on the rafter joist ends that mate up to the top plate or header. Check overhang to calculate rafter overhang equal to the lower level cut at the full rafter depth. Move slider or directly enter angle to alter sweep angle of lower rafters and change the shape.

Don t forget to include any overhang and make sure you input measurements as a single number 2 25 instead of 2 3. Move slider or directly enter angle to alter sweep angle of lower rafters and change the shape. Gambrel roof framing geometry calculator inch this gambrel roof fits in a semicircle and starts as the top half of an equal sided octagon. With overhang selected drag slider to increment decrement birdsmouth seat width to suit.

If you want to do these pitches you just need the width. For overhang you ll have to use a 30 60 90 to figure out the added width. Draw a semi circle on the graph paper mark a center peak at the top and draw two lines on each side in the shape desired for the gambrel roof. Since the sum of the three angles in a gambrel roof is 180 degrees the angles you will need are as follows.

Span 2 73 will get you equal parts at these angles. The preview drawing displays a dimensioned elevation view of the gambrel roof. Use the protractor to measure those angles at the peak the walls and the point where the two lines intersect on the top side of the roof. Check overhang to calculate rafter overhang equal to the lower level cut at the full rafter depth.