How to Flash a Dormer Metal Roof

Dormers are add-ons for buildings where the homeowner wants to have extra space with a window looking out from a room. The dormer protrudes outwards from the rest of the roof, usually in a sloped setting, and has its own peaked roof. However, the overall dormer also connects to the other roofing material for the home, and flashing is a requirement anywhere where there are inside and outside corners. For metal roofs in particular, there are flashing strips that you can install under the roof material to protect the home from water damage.

Drill
Inch and a half galvanized self-tapping screws with rubber gaskets
Silicone caulking
L flashing
Peak flashing

Instructions

- 1
  Apply silicone caulking to the back sides of the flashing, slide it in place and screw it down on the horizontal section with the screws and drill. Install the L flashing so that the vertical section sits along the face of the roof lip edge, and the horizontal section rests on top of the dormer roof. Flash all of the outside edges of the roof for the dormer itself where the edges of the dormer roof terminate.
- 2
  Cover all of the inside corners where the dormer meets the roof of the house with the same L flashing, but invert it, with the vertical section running up the wall of the dormer and the horizontal section on top of the roof for the house.
- 3
  Apply silicone caulking to the underside of the edges, and place the flashing over the top of the peak of the dormer roof where the two angles of the roof meet after the roofing material -- shingles or panels -- is in place. Screw the edges down on top of the roof material.

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