Cut a common rafter for a pattern and lay it on the drawing to check for fit.
Make the full-scale drawing to the dimensions and roof slope in your plan (Figure B) and use it to measure the exact height of the ridge (temporary post) and the lengths and angles on the common rafters. If the slope of your dormer roof is the same as that of the old roof, you can use the roof jig technique shown on p.
Construct a simple jig for marking the common rafters. For the two valley rafters, use the same dimension for the "plumb" side but extend the "level" side to 17 in.
Skylights are manufactured with
common rafter spacing in mind to minimize the number of rafters that need to be cut.
The gable rafters (H) are the same as the common rafters except they sit atop the front and rear headers, so they need to be scribed (Photo 10) to fit.
SIZE & DESCRIPTION A 12 5-1/2" x 5-1/2" x 10" treated pine (posts) B 2 1-1/2" x 9-1/2" x 153" treated pine (front and rear headers) C 2 1-1/2" x 9-1/2" x 128" treated pine (side headers) D 2 1-1/2" x 9-1/2" x 150" treated pine (inner front and rear headers) E 2 1-1/2" x 6-1/2" x 113-1/2" treated pine (side rafter supports) F 1 1-1/2" x 9-1/2" x 131-1/2" treated pine (ridge beam) G 10 1-1/2" x 3-1/2" x 74-7/8" treated pine (common rafters) H 4 1-1/2" x 3-1/2" x 74-7/8" treated pine (gable rafters) J 30 3/4" x 2-1/2" x 139" treated pine (roof slats) K 2 1" x 2-1/2" x 12" treated pine (ridge cover plate) Note: The dimensions given here may vary slightly--measure before you cut!
The common rafters (Photo 6) are all the same length and have the same miter cut at the top and the same "bird's-mouth" or notch cut near the bottom.
This miter angle differs from that of the common rafters (Fig.
E) rest on the header just like the common rafters and have the same degree measurement at the top.
