How to Install Roll Roofing

Install drip-edge flashings, roofing felt, and WSU, if needed. You can install metal valley flashing, but it is common to simply apply an 18-inch-wide strip of roll roofing instead. Set it in a bed of roofing cement, smooth out any creases, and drive nails near the edges.

Position the first course so it overhangs the drip edges by about 1/4 inch and roll it out a distance of 8 feet or so. Drive nails every 3 inches along the rake at one end, pull it taut, and drive nails along the eave edge. The nails should be about 1 inch from the edges. For extra protection add a 3-foot-wide strip on top of the 18-incher.

The next sheet overlaps the first by 4 inches or with some types of roll roofing, enough to cover the area that is bare of mineral surfacing. Snap a chalkline indicating the top of the next sheet, roll it out along the line, and drive nails as for the first sheet.

Plan so that no two butt joints are closer than 2 feet from each other. Spread a 6-inch-wide layer of roofing cement on the edge of the first sheet and embed the next sheet in the cement.

To seal a plumbing vent, spread roofing cement around the pipe. Cut a hole in a piece of roofing about 2 feet wide and slip it over the pipe. The piece should overlap the lower course by at least 4 inches. Cut a hole in the roll roofing and slip it over as well. Embed both roofing pieces in cement. For added protection add a boot flashing.

Work from one side roof past the center of a valley by 2 feet. Then, working from the other side, overlap the valley, strike a chalkline, and trim the piece at the center of the valley. Keep nails at least 12 inches from the center of the valley; use a 4-inch-wide bed of roofing cement to attach everything that is closer than 12 inches.

In most cases you can simply overlap the sheets at the ridge using roofing cement and nails for the final piece. However if the final piece does not come down at least 8 inches past the peak, cover the peak with a 16-inch-wide strip that is embedded in cement.

If you have a sloped roof, cut strips of roofing 9 inches wide, position them flush with the drip edges along the eave and rake, and attach them by driving two rows of nails that are about 3 inches apart. Use a trowel to spread roofing cement over half or more of the strips.

Then, set the first course in the cement so it overhangs by about 1/4 inch. Position and roll out the roofing carefully because it is not easy to reposition, then press it into the cement. Nail only its top edge (the part that is bare of mineral coating). Coat the top edge with a 4- to 6-inch-wide layer of roofing cement and apply the next courses in the same way.