How to Install a Modified-Bitumen Roof

Cut loose material from the existing roof with a utility knife. Cut bulges and dips from the existing roof's surface with the knife. Scrape large areas of damaged or deteriorated roofing with a roofing scraper. In general, it is acceptable to apply built-up roofing over previous roof coverings that are clean and structurally stable. Sweep the roof's surface with a push broom to remove dirt, gravel and debris.

Inspect the roof's flashing for rust and deterioration. Pry damaged flashing from the roof with a pry bar. Spread roof sealant across holes and gaps with a putty knife. For both new and old roofs, cut flashing to size and fasten the flashing to the roof with a hammer and roofing nails roughly every 12 to 18 inches. Seal the flashing's edges and fastener's heads with roof sealant and a putty knife.

Unroll a rolled roofing starter strip along the roof's eave line. Trim the strip to length with a utility knife. Hang the strip roughly 1/4 inch over the roof deck's edge. Fasten the strip to the roof deck with two rows of roofing nails located 1 inch in from the top and bottom edges, spaced every 4 inches. Apply similar starter strips to the roof's rakes.

Unroll a full-size sheet of rolled roofing along the roof's eave. Trim the sheet to length with a utility knife. Align the sheet's bottom edge with the edge of the underlying starter strip. Fasten the sheet to the roof deck with a row of roofing nails located roughly 1 inch below the sheet's top edge, spaced approximately 16 inches apart. Lift the bottom edge of the sheet and use a roofing brush to spread a thin layer of cold-applied lap cement to the underside of the sheet's bottom edge.

Press the coated edge onto the starter strip. Finish fastening the first full-size course to the roof deck with two additional rows of nails, one row roughly 1 inch above the sheet's bottom edge and another roughly 12 inches above the bottom edge. Space the lower row's nails roughly 8 inches apart and the middle row's nails roughly 16 inches apart.

Unroll a sheet of rolled roofing across the first sheet. Trim the sheet to size with the a utility knife. Overlap the bottom edge of the second sheet at least 2 inches over the first course of rolled roofing. Nail the top edge of the second course, following the same nailing pattern as the first. Lift the bottom edge of the second course. Apply cold-applied lap cement to the underside of the second course.

Press the coated edge onto the first course. Finish fastening the second course, following the nailing pattern of the first course. Brush lap cement across the top of the overlapping portions of the first and second courses. Apply successive courses of rolled roofing, overlapping at least 2 inches and coating both the underside and tops of laps with cement. Cap ridges and hips with a strip of rolled roofing that overlaps underlying sheets by at least 6 inches. Run a roofing roller across the installed roofing after allowing the cement to set for a few hours.