How To Figure Gambrel Roof Angles

Gambrel roof framing geometry calculator inch this gambrel roof fits in a semicircle and starts as the top half of an equal sided octagon.

How to figure gambrel roof angles.

Gambrel roof framing geometry calculator metric this gambrel roof confines to a semicircle and starts as the top half of an equal sided octagon. Check overhang 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. Span 2 73 will get you equal parts at these 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. 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. The preview drawing displays a dimensioned elevation view of the gambrel roof. 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. 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. You will need to make 22 5 degree angle cuts on the rafter joist ends that mate up to the top plate or header. If you want to do these pitches you just need the width.

Since the sum of the three angles in a gambrel roof is 180 degrees the angles you will need are as follows. Calculate gambrel angles with graph paper and a protractor. Check overhang to calculate rafter overhang equal to the lower level cut at the full rafter depth. 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.