How to Install Step Flashing in a Fine Home

Install step flashing up a sloping roof alongside a wall from the bottom up and in steps. Cut the first piece of flashing with tin snips on the center fold line, bend the roof side down over the eave and nail the top to the house siding. Bend the cut piece from the vertical half in toward the roof, to form a "kickout," so water running down the joint will be redirected away from the wall.

Nail flashing only to the house sheathing, never to the roof decking. Use galvanized, aluminum or copper nails that conform to the flashing material. Put a second piece of flashing over the first, overlapping the seam. Alternate with shingles, so each piece of flashing laps over part of a shingle below and under part of the next shingle above, to seal the joints between shingles, which the next course of shingles will then cover.

Run flashing over one side of a peak, cut it at the fold line, nail the top part to the wall sheathing and fold the bottom part down over the peak. Run flashing from the other side of the peak the same way, over the peak, cut at the fold line, nailed up the wall and bent down over the abutting flashing. Cover all flashing with shingles or wall siding.

Put flashing around a chimney or similar vent starting at the bottom. Cut it at the fold line and wrap it around the corner, just like at the peak of a roof. Install counter flashing on a chimney, a second piece of flashing put into the mortar joints between bricks or into slots cut into the chimney, with one side bent down to seal the top of the step flashing.

Place step flashing over an underlay on roof decking. Put it on wall sheathing before bricks or stucco are installed, if possible, so the wall side of the flashing will be located under the brick or stucco. Use roofing caulk to seal the top of the flashing to bricks and stucco on walls that have already been already built.