How to Frame a Large Shed Roof

Install trusses starting at the back of the shed. Mark the outer wall caps first, with parallel locator lines 1 1/2 inches apart. Use a tape measure, marker and speed square to draw a line across the wall cap 1 1/2 inches in from the end of the wall. That is the location for the first truss.

Measure 23 1/4 inches in and draw a line for the outside edge of the second truss; add a second line 1 1/2 inches farther. Measure 24 inches from that line and draw another pair, then mark truss locations every 24 inches to the other end of the roof. Mark both outer walls identically.

Lift the first truss to the roof upside down and set it upright. Secure it to the wall caps on either side with 16d framing nails, driven with a hammer diagonally through the truss end into the cap board. Use three nails, two on one side of the truss, one on the other. Plumb that truss vertically with a level and brace it with 2-by-4-inch boards nailed to the truss and to stakes in the ground.

Set two more trusses the same way. Plumb them and nail them to wall caps, then brace them temporarily with 1-by-4-inch boards nailed across the outsides of the truss members on both sides. Add trusses to the other end of the roof, bracing every three trusses. Install permanent lateral bracing once all trusses are erected; this varies and can be as simple as 1-by-4s nailed diagonally between sets of three trusses.

Remove the temporary braces once permanent bracing is in place. Nail short sections of 1-by-2-inch boards vertically on the ends of each truss to serve as braces and alignment markers for OSB sheathing. Nail 4-by-8-foot panels of OSB to the truss rafters with 8d galvanized nails, spaced about a foot apart. Set full panels and trim excess at ends and the top of the roof with a circular saw. Overlap one OSB panel over the edge of the other side at the roof peak.

Roll out roofing paper horizontally on both sides of the roof, starting at the bottom. Fasten it to the OSB with a construction stapler. Overlap paper 6 inches from the top. Fold one layer across the peak and staple it on both sides.

Cut the tabs off one row of three-tab asphalt or composition shingles with a utility knife. Spread a bead of roofing cement on the bottom edge of the roof and nail those shingles to the OSB, upside down with the cut edge on the roof. Fasten shingles with roofing nails about 6 inches apart at the tops. Add full shingles up the roof; cut one tab width off the second row of shingles so the seams do not align.

Finish the peak with special cap shingles if provided or by folding the cut-off tabs over the peak. Install cap shingles pointing away from any prevailing wind. Nail cap shingles on both sides of the peak toward the front. Add a bead of roofing cement on the back edge if desired for added security. Cover the peak to the other end of the roof and cover the last set of nails with roofing cement.