Roof Leak

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Posted by: from Banff
4/2/2020 at 9:17:55 AM

I built a flat roof for an extension on my house. I put water and ice underlayment on then shingled it. Now I have l leaks where the roof meets the house and 8 feet away from the house. Can I put a liquid sealant over the shingles?

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Date/Time4/2/2020 at 11:06:29 AM

Hey there Gary,

What kind of liquid sealant are you planning on using?

I recommend using "Supra Expert Sealant" for any affected areas you may have to mitigate the problem.

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Date/Time4/2/2020 at 11:08:03 AM

Flat roofs are not suppose to be shingled.There are various 1ply and 2 ply sbs roofing membranes that are self adhesive to do this application.That being said a best approach would be to add a wall flashing termination under the eavestrough against the house fascia and fasten to the new addition.Any sealant or tar is not a solution as it would crack from expansion and contraction.You can get these counter ir wall flashing at any roofing supply store.

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Gary in Banff
Date/Time4/2/2020 at 11:41:34 AM

Thank you Jason. Should I remove the new shingles I put down?

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Date/Time4/2/2020 at 2:35:45 PM

Hi Gary,

As mentioned in a previous comment, shingles are not suitable for a flat roof, or even anything under a 3/12 slope. I would be hesitant to put them on anything under 4/12.

I would say that you will need to remove the shingles to rectify this in any sort of long-term or permanent way.

Use a flat roofing product that will have no penetrations due to nails, as you would with shingles, and get some metal wall flashing for the transition from the house wall to the new flat roof.

Good Luck,


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Date/Time4/2/2020 at 7:37:47 PM

Hi Gary,

Hate to be the bearer of the news, but you need to re-do the roof from scratch, really. Shingles are for pitched roofs, flat roofs need to have a single membrane applied.

The elastomeric material goes down like sheets of rubber, and is sealed together in stages.

Here is a link that might help:

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Date/Time4/2/2020 at 8:38:00 PM

Gary, You can and it may or may not solve the problem. Flat roofs have issues because, even with a slight slope, the water doesn't flow strong enough to drain as it should. The best answer would be to use a rubberized membrane, better than Ice Guard, over the entire roof and then shingle, if that is the look you want. Or, install metal roofing for the non-nailed results and eliminating multiple mails and nail holes. It only takes a very small hole to create a leak.

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Date/Time4/4/2020 at 12:47:21 PM

In short, no,

Don't spend any more good money after bad.

You don't know what you are doing.

Hire a good roofer

Obtain a warranty.

Spend your time on something else that will help pay for the cost.

Have no worries.


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