How To Figure Gambrel Roof Angles

If you want to do these pitches you just need the width.

How to figure gambrel roof angles.

With overhang selected drag slider to increment decrement birdsmouth seat width to suit. 45 degrees where the joists meet up with the top plate or header and 90 where the joists meet in the middle at the ridge board. 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.

Calculate gambrel angles with graph paper and a protractor. Move slider or directly enter angle to alter sweep angle of lower rafters and change the shape. Check overhang to calculate rafter overhang equal to the lower level cut at the full rafter depth. Check overhang to calculate rafter overhang equal to the lower level cut at the full rafter depth.

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. 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. With overhang selected drag slider to increment decrement birdsmouth seat width to suit. Span 2 73 will get you equal parts at these angles.

You will need to make 22 5 degree angle cuts on the rafter joist ends that mate up to the top plate or header. For overhang you ll have to use a 30 60 90 to figure out the added width. Since the sum of the three angles in a gambrel roof is 180 degrees the angles you will need are as follows. Gambrel roof framing geometry calculator metric this gambrel roof confines to a semicircle and starts as the top half of an equal sided octagon.