How To Flash A Roof Dormer

Roof shingle over step flashing.

How to flash a roof dormer. You may want to paint the flashing to match the roof. Step flashing on roof peak. Fasten one edge of the flashing up the dormer wall with flashing nails and lay the other side flat on the main roof. If you do not wish to form your own corner flashing you can buy pre bent pieces and cut them to size or use a piece of corrugated aluminum which is easier to bend.

Bend the corner flashing tightly around the corner. A critical juncture that often fails is where these two flashings meet. While the gold standard for roof flashing is soldered copper the fact is that for economic reasons the vast majority of roof flashing is done with aluminum. One common method is to lay the edge metal under the eaves membrane and over the rake details concrete masonry roofing wrb flashing.

Apply peel and stick membrane to the front wall of the dormer making sure it overlaps the roof underlayment and wraps up onto the wall 6 or 8 inches. Coat the flashing with a zinc based primer followed by two or more coats of spray on rust preventive metal paint. First use a stiff wire brush and solvent to clean the surface of any dirt debris or corrosion keep solvent away from asphalt shingles. Shed dormers require a continuous strip of flashing along the top of the lower roof plane where it meets the steeper roof plane.

When installing trim provide sufficient clearance as shown or use a moisture tolerant material such as pvc or boral. Use taller pieces of step flashing towards the top so the pieces can be bent over the dormer roof to help keep out snow and wind blown rain. In this article veteran remodeler mike guertin shows how to flash a dormer with bombproof details. Here s a step by step look at how to flash a dormer so that water is carried away from those vulnerable areas.

1 install roof underlayment up to the dormer cutting it a few inches short of the roof wall joints at the front and side walls. Two ways to flash roof edges protect the eave from ice dams and sideways rain step one in steep slope roofing is the edge flashing.