Flashing The Dormer Peaks

The point at which the peak of the dormer meets up with the main roof is one that has to be flashed carefully. In addition to using the peel-n-stick flashing, I've built up another layer of protection using aluminum strip-flashing.

I first cut a piece of aluminum L-flashing about 2' long. I cut along the fold line for about 8" and then fold the ends up a bit. I then lay it over the peak of the dormer with the two legs laying flat on the upside of the main roof. I don't put any nails within 6" of the peak of the dormer.



Then I cut a piece of 9" flat aluminum stock about 12" long. I cut a V-shape out of one end, and lay it down over top the first piece of flashing. I then put a generous amount silicone sealant along the seam where the two pieces overlap.



Lastly, I lay another piece of peel-n-stick flashing over the top edge of the aluminum flashing. Once the shingles are in place, I don't think I'll have any problems with water coming in here.

The most important thing to remember about roofing is that for any for any two pieces of roofing material... whether it be tar paper, or peel-n-stick flashing, or shingles... the upper piece must always overlap the lower piece. Always. Always. Always.

Flashing The Front Of The Dormers

Any time there's a change in a wall-to-roof plane, it's a possible trouble spot for moisture problems. I've installed aluminum flashing (known as apron flashing) where the main roof meets the front wall of the dormer. The flashing sits on top of the shingles and then continues up the wall underneath the housewrap. This gives the best protection against water getting underneath the shingles.

At the corners of the dormers, I've also fashioned a kick-out flashing which continues past the step flashing. This will prevent water from running down the side of the dormer and turning the corner to possibly get in underneath the apron flashing.

Once everything was in place, I added a bit of silicone sealant to the inside seams and brought the housewrap down in front of the flashing.