You may object to a metal roof. It may not be in keeping with the rest of the buildings on your property or you may want to use leftover roofing materials from other projects. Wood shingles or asphalt shingles can be used, but they are unnecessary and expensive for this kind of structure.
Any roof other than a metal one will require decking and of the roofs requiring decking, roll roofing is the fastest, easiest, and least expensive to lay. It is especially suitable for roofs with such a shallow slope and costs 15 percent less than asphalt shingles.
The rafters should be spaced on two-foot centers. (This will necessitate another 2 x 6 x 12.) The plywood sheathing of 4′ x 8′ x ½″ exterior grade is nailed directly to the rafters. Begin at the rake (the side edge of the roof), and lay the plywood with the face grain perpendicular to the rafters. Nail the sheet in place with 6d nails spaced every six inches at the edges and every twelve inches at the rafters in between. To insure that the nails don’t miss the rafters, snap chalklines along the rafters. Lay the second piece in place leaving 1/16-inch space between the two.
Protect the roof with a drip edge around the eaves and rakes. It should fit snugly. Drip edge can be cut with tin snips. Nail it down with roofing nails centered in the top surface and spaced every twelve inches.
Start laying the roofing from the rake. Cut to length plus ½ inch a starter strip nineteen inches wide from the selvage portion of the roll. This will leave a ¼-inch overhang at each edge. The seventeen-inch remaining strip that has the crushed mineral surface will be used for the last course. Lay the smooth tar-coated piece in place, leaving a slight overhang on three sides. Fasten it with roofing nails spaced one-foot apart in three horizontal rows. Locate the nails about six inches apart. Use galvanized roofing nails.
Cut the next strip to length using the full width of the roll roofing. (Add ½-inch for the overhang.) Nail it down in two rows eight inches apart and the nails spaced every twelve inches. Lift the mineral surface of each course and coat the upper nineteen-inch portion of the previous strip with quick-setting asphalt cement to within ¼ inch of the exposed edge. Roll the mineral surface back into place.
Each succeeding strip should overlap the previous one by nineteen inches, with seventeen inches of the mineral surface exposed at each course. The upper portion of each strip should be cemented. Use the coated half left over from the starter piece for the last strip.
After the roof has been finished, check for any loose laps and re-cement them.
Many people think roll roofing is unattractive. However if the job is done neatly, none of the nails or cement should show. And if the roof is almost flat yet eight feet high, it shouldn’t be visible.