# Roof Leak When Rain is Wind Driven



## Windows on Wash (Aug 30, 2011)

Wind does drive water, but there are plenty of dormers that are water tight out there. 

Usually when it comes to dormers, to un-do what the builder did, you need to pull up trim, siding, wall cladding, etc. to install proper flashing, membrane/underlayment. 

No reason it shouldn't not leak. Just a question of how deep you need to go for the repair.


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## joecaption (Nov 30, 2011)

Most dormers I've had to go back and fixed where not sided or flashed correctly.
Where's it leaking, at the bottom corner?


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## kc27 (Oct 24, 2009)

Thanks for the replies.

To answer the question about the location of the leak: it is a small drip from the ceiling about 3' from the north edge of the dormer and approximately 9' from the front edge. I put some links to photos below.

When the roof was replaced in 2003, it had three layers of shingles on it. This was a tear-off, which left the gap you see filled with flashing between the single layer roof and edge of the dormer siding. I had no leaks for 12 years in any weather conditions. But in the last couple of years, any wind blown horizontal rain causes the leak on the ceiling of the dormer.


House profile
Rear of dormer
Close-up of rear dormer wall
Dormer from front


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## Nehmo (Oct 25, 2016)

kc27 said:


> it is a small drip from the ceiling about 3' from the north edge of the dormer and approximately 9' from the front edge.


Because water travels between the ceiling and the roof, it's difficult to tell from the bottom where the problem it on the top. But you have a dormer leak, and these are common.
On your 02_dormer_labeled.jpg , the bottom flashing doesn't extend beyond the dormer walls. You can start by just trying extending that.








I'm going to describe a repair. This is going to be a repair, which is different from new construction. Don't bother with step flashing; it's too complicated. Just use one (or 2 if necessary) long pieces. The actual leak is probably at the bottom of the dormer junction of the dormer wall and the roof.
♦Unfasten all the nails that fasten the siding to the dormer on the side near the pitched roof surface. That is, loosen the siding on the inside side of the dormer. 
♦Get a 4"x4" (or so) L-shaped length of aluminum sheet metal the length being the distance between the gutter and the ridge (all the way).








♦ Ideally, the upper facing side would be the same color as the shingles. Paint with a can of spray paint.
♦ Overlap 2 two pieces in shingle fashion (lower one under upper one) to make the length if you don't have one long enough.
♦Install one side of the flashing under the siding. If your piece of angled sheet metal has different length legs of the L, use the shorter side under the siding. 
♦Trowel some mastic (plastic roof cement) into the junction of the dormer wall and the roof under the metal. Do the whole line. You can't use too much roof cement.
♦Go as high as you can with the flashing, and on the low end go all the way to the gutter. This leaves a vertical piece of the flashing exposed. Big deal.
♦The flashing goes under the siding and over the shingles.
♦Refasten the dormer siding and in the process secure the flashing in place. 
♦Over every exposed nail, smear some roof cement. Wait a few days for it to harden, and then spray paint over to protect it from UV light.


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