Leaking Dormer -

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Joined: Mon Apr 09, 2018 4:43 am

Leaking Dormer -

Post by scurtiss » Mon Apr 09, 2018 5:00 am

Can you double up 15 Lb Tar paper? I am repairing a dormer on a house that has been re-roofed. I need to build up the layers . What is the best way to do that?

The leak came because the old flashing was directing the water under the shingles. It looks like I have to add layers to the existing roof, and re-flash using step- flashing. Any ideas would be appreciated.
see attached picture.
Dormer Leak
20180408_184137.jpg (84.4 KiB) Viewed 98 times

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Re: Leaking Dormer -

Post by Shannon » Mon Apr 09, 2018 7:04 am

Yes you can double up tar paper . You defiantly need to get the flashing shedding water out from under the roofing. To install new step flashing to this all properly you will need to remove the siding and re-install afterwards.
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A. Spruce
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Re: Leaking Dormer -

Post by A. Spruce » Mon Apr 09, 2018 11:32 am

I would not use 15# felt, nor would I stack it in layers to "shim" up under the shingles.

15# felt is a poor choice, 30# is much stronger and more durable, especially when you're patching like you are. As you are layering your patch, it is important to maintain the correct orientation of the layers so that water is always shed to the surface.

Rather than using felt as your "shim", use shingles. On the bare deck you will lay your felt so that it's sides and bottom edges overlap the existing felt by at least 6". Then, lay shingles to fill the void, the same as you would the top layer so that water is naturally shed to the outside. Another layer of felt installed just as before, then your finish layer of shingles.

Step flashing is installed over the top of the shingle, though it doesn't necessarily have to be exposed, so long as any water it is redirecting is done in a manner that it always finds it way to the surface. Shingles should be held back from touching the vertical face of the flashing for less opportunity for the water to be wicked under the shingle. The space should also get slightly wider as it gets to the bottom to prevent debris from backing up.
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