How to Cut the Rafters for an A-Frame House

Review your building plans to find the roof pitch of the house. It will be listed as a fraction, 6/12 (rise over run) for example. This means that for every horizontal foot, the roof rises 6 inches.

Lay your framing square on the rafter with the tongue (short leg) measurement for rise and the body (long leg) measurement for run aligned with the top edge of the rafter. Mark a cutline across the rafter using the tongue (short leg) of the framing square as a guide. Cut along the cutline with your circular saw for the first fascia board cut.

Flip the framing square so that the body points toward the piece you just cut. Align the rise and run from the pitch with the bottom edge of the rafter. Mark a cutline using the bottom edge of the body as a guide. Cut along the cutline to complete the fascia cut.

Flip the framing square back to the top edge of the rafter. Slide it 10 1/2 inches up the rafter, align the rise and run measurements and draw a plumb line using the outside edge of the tongue as a guide.

Flip the framing square back to the bottom edge of the rafter. Align the rise and run and draw a seat line using the bottom edge of the body as a guide.

Cut out the area beneath the triangle formed by the cut and seat lines.

Move the square 1 foot along the rafter for every foot of rafter length, as specified by your building plans. Draw a ridge cutline using the bottom edge of the tongue as a guide. Cut along the cutline to complete your rafter.