How to Frame a Run-In Shed Roof

Frame a roof for a 12-by-12-foot run-in shed, a typical size, with 2-by-4-inch rafter boards and a 2-by-6-inch ridge board. Use 12-foot boards for long slope rafters and 3-footers for the short slope, both figured for a 7/12 pitch, which rises 7 inches per foot. Mark the tops of a pair of rafters to a 7/12 pitch by putting the pivot point of a speed square at the top edge of the board and aligning the 7 on the "common top cut" table at the top of the board.

Measure 27 inches down on the short board with a tape measure and cut a reverse angle by putting the pivot point at the bottom of the board. Measure 3.5 inches up from the end and draw a vertical line 1 inch into the bottom of the board. Connect the top of that line with the end of the board to form a triangle to fit on the 4-by-4-inch outside beam.

Mark the long rafter by measuring 135 inches down and figuring another reverse angle; this allows for a 6-inch overhang at the back. Draw a triangle by marking the bottom of the board at 6 and 9.5 inches, with a vertical line at the upper mark. Connect those for a triangle to fit on top on the back wall top. Cut angles on one pair of rafters with a circular saw and test fit them to ensure the triangles are secure and the ends come together at the top.

Cut six pairs of rafters to that pattern. Set one pair at one end of the shed and nail the ends to the back wall and front beam with 16d framing nails and a hammer -- two nails on one side, one on the other on each rafter. Let the rafter tops rest loosely against each other. Set another pair of rafters at the other end of the shed. Use a level to get both sets of rafters plumb.

Install a 12-foot long 2-by-6-inch ridge board between the end rafters. Lift it to the roof and slide it between the end rafter tops from the bottom. Use a 4-foot level to get it level and fasten it with two framing nails through each rafter top. Install other rafters, in pairs, spaced 24 inches apart.