How to Install Roll Roofing Over an Existing Roof

Roll roofing is an asphalt-based material sold in rolls. The material is 36 inches wide by up to 90 feet long. Roll roofing's advantages are that it is less expensive than asphalt shingles and easier to install. However, because roll roofing is not as durable as asphalt shingles, it has a shorter life span. Another advantage to using roll roofing is that the product is suitable to install over existing shingle or roll roofing roofs. This quality leads to reduced labor costs, adding greater savings to the project. Roll roofing is generally not as visually attractive as shingles, but it provides an adequate solution for leaking roofs.

Rolls of tar paper
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Roll roofing is a type of asphalt roofing material.

Step 1

Sweep the roof area with a broom to remove any dirt, debris or organic material to provide a clean surface. Remove or hammer down any loose or exposed nails. The object is to provide a clean and flat surface for the roll roofing installation.

Step 2

Install the felt paper first. Starting on the bottom edge of the roof, roll out an adequate length of felt paper and cut it with a razor knife. Fasten the felt paper on its bottom edge using a hammer and felt paper nails. An adequate distance for nail spacing is about eight inches but depends on building codes in your area.

Step 3

Install the second row of felt paper, allowing it to overlap the first row by four inches. Fasten the second row on the bottom edge where it overlaps the first row. Continue this process until reaching the top or peak of the roof and repeat for the other side, if applicable. For two-sided roofs with a peak, install a row of felt paper that covers the length of the peak while overlapping the last rows on each side of the peak.

Step 4

Install the eave drip around the perimeter of the roof on top of the felt paper. The eave drip diverts water runoff from the roof away from the fascia board. Start on one corner of the roof and place an eave drip into position. The eave drip should rest flush against the fascia board and the top of the roof. Fasten the eave drip by installing galvanized roofing nails about every eight inches along the top side of the eave drip. Overlap the second piece of eave drip with the first by about two to three inches and fasten with roofing nails. Use a pair of tin snips to cut lengths of eave drip as needed.

Step 5

Apply a layer of roofing cement about four inches wide around the roof perimeter directly on top of the eave drip using a plastic or disposable putty knife. The roofing cement secures the edge of the roll roofing to the eave drip around the roof edge.

Step 6

Install the first row of roll roofing on the bottom edge of the roof. Cut the roll roofing to length using the razor knife. Position the length of roll roofing so that it spans the entire distance and is flush with the edge of the eave drip. Press the bottom edge of the roll roofing into the roofing cement to attach it to the eave drip.

Step 7

Nail the top edge of the first row of roll roofing using the roofing nails about every eight inches.

Step 8

Apply a layer of roofing cement about 1/2 inch thick and 4 inches wide across the top edge of the first row of roll roofing. The cement secures the bottom edge of the next row of roll roofing. Continue this process until reaching the top of the roof. Make sure to press the ends of the roll roofing into the roofing cement to secure. If applicable, repeat this process for the other side of the roof.

Step 9

Complete the roll roofing installation by capping the peak with a length of material. The cap attaches to the top of the last rows on each side with roofing cement.