How to Frame a Storage House With Rafters

Tie the walls of a storage house together with roof joists, beams fastened on top of the outside wall caps at 24-inch intervals starting 1 1/2 inches in from each end wall. Use metal joist hangers, fastened to the caps and beams with 8d galvanized nails and a hammer. Place the hangers, set 2-by-6-inch beams in them on edge and nail the beams in place.

Determine a pitch for the roof, the angle at which it slopes from a center peak to a wall, and figure the rafter run, the space each rafter will cover from peak to wall, half the width of the building. Use at least an 8/12 roof pitch, which rises at 8 inches per foot from wall to peak.

Lay an 8-foot 2-by-4-inch board on a flat surface with the 4-inch side facing up. Put the point of a framing square at the bottom of one end of the board. Align the 8-inch mark on the thin tongue of the blade and the 12-inch mark on the wide blade at the top of the board to form an angle at the end of the board called a plumb or top cut. Mark that with a pencil.

Figure the length of the rafter with the "common rafters" table on the blade. Find the length differential under the pitch, 8-inch, mark. Multiply that, 14.42, times the rafter run, 5 feet for a 10-foot wide storage house, for instance. Round that sum, 72.1, to 6 feet.

Measure with a tape measure 6 feet down the bottom of the board from the plumb cut. Draw a vertical line there 1 inch up into the rafter board. Measure from the bottom of that line 3 1/2 inches back up the board. Connect that point and the top of the vertical line to form a triangle, called a birdsmouth, to sit on top of the wall cap.

Add an overhang to extend beyond the wall, typically about a foot, and mark an angle the reverse of the plumb cut. Put the point of the square at the top of the board and align the tongue and blade just like at the other end. Draw that line. Go back to the plumb cut, measure 3/4 inch down and draw an identical angle; this allows space for a ridge board between two rafter tops.

Mark and cut all rafters to that pattern with a circular saw. Divide the length of the roof by 24 to get the number of rafters needed, allowing for two rafters every 24 inches. Set the first pair of rafters at the back of the roof, against the roof joist. Fasten them to the wall caps and to the joist with 16d framing nails driven with a hammer. Put two nails on one side of the rafter, one on the other and two into the joist. Let the rafter tops rest against each other. Use a level to plumb the rafters.

Install another pair of rafters at the other end of the roof, outside the joist on that end, and fasten them the same way. Lift a 2-by-6-inch ridge board into place between the end rafter pairs. Slide it up from the bottom between the rafter tops, level it with a level and nail the rafters to it, two nails in each rafter into the ridge.

Set all other rafters in place alongside the joists. Nail each rafter to the wall cap, the joist and the ridge board. Install purlin braces on the undersides of the rafters to tie them together in sets of three. Secure the first three back end rafters with purlins, start the second set with a purlin on the third rafter below the first brace, and work that way the length of the roof. Add roof decking and rigid roof insulation.