How to Install Roof Flashing

Roof planes that butt up against vertical walls at the end of each new shingle course need to be protected by installing metal step flashing. Metal step flashing pieces are rectangular, approximately 10 inches long and at least 2 inches wider than the face of the shingle being used. For instance, when using metal flashing pieces with IKO Advantage Size Laminated Shingles, which have a 5 7/8-inch exposure, the size of the flashing will typically be 10 x 8 inches. Other sizes are acceptable for local code allowances, so be sure to check yours. The 10-inch length is bent in half so that 5 inches will reach up the wall surface and the other 5 inches will extend onto the roof deck. Place a piece of step flashing on top of the first row of shingles that butts up against a vertical wall or structure. Embed each step flashing piece in a 3-inch-wide application of asphalt plastic cement and nail to the roof deck with two nails. Do not nail the flashing pieces to the vertical wall. This will allow the flashing pieces to move with any differential expansion and contraction that may occur between the roof deck and the wall. As you make your way up the roof, ensure that you position the metal flashing piece in each core so that the overlaying shingle will cover it completely. The end of the shingle in each course, if installed with the correct shingle exposure, will overlap and conceal the step flashing. The end of each shingle adjacent to the wall must also be embedded in a 3-inch-wide application of asphalt plastic cement. Flashing pieces and shingles in each course are installed on asphalt cement and nailed accordingly in succeeding alternating overlapping steps up the roof. Flashing laps should never buck or obstruct the flow of water. Chimney flashings are secured to the roof cover of the shingles and counter or cap flashings are secured to the chimney, providing a waterproof seal. For pipe flashings around soil stacks, shingle up to the bottom of the stack, then slide the new flashing over the soil pipe and into place. Nails for securing the flashings to the roof should be used sparingly, where the flashing manufacturer recommends, and not be driven close to the pipe. Continue shingling, cutting to fit around the stack. Each cut shingle should be laid in a bead of asphalt plastic cement. We recommend putting a dab of asphalt plastic cement over the exposed nails to seal against leaks. Great job! By flashing vulnerable areas of the roof, you are helping prevent water infiltration.