Flat roof coating

7 Replies

Hi all,

I have a fourplex with a six year old flat roof that is around 3600 square feet. There are a few spots where water is puddling, and it looks like it could use a protective coating rolled on. Does anyone have any advice on which coating to use? Home depot and Menards both carry multiple types of products, and since it is going to cost a good bit I want to make sure I get the right type!

Torch down rubber roof. If you have a really low spot you can lay a piece of plywood down and torch over it.

I think my post was confusing. The roof is already on, but I am trying to find what type of protective coating people have used successfully. I believe I have a "torch down" style roof currently. 

@John Warren - There is no such thing as torch down rubber. Nine chances out of ten the roof is a modified roof (asphalt chemical composition; essentially a one square shingle) which is applied using a torch or set in cold process (roof cement). Are the seams approximately 33" apart? If so, that's definitely modified. Ponding generally forms when there is deflection in the substrate (deck) or the insulation is crushed or wet. If the insulation is wet, it should be replaced so the substrate does not deteriorate from the moisture, compounding the problem.

Once you've determined what is causing the ponding and address it; your next step would be to pressure wash the roof area to remove any coating no longer adhered to the roof system. DO NOT USE ANYTHING HIGHER THAN 2000 psi! Once the failing coating and debris is cleaned away, reapply a coating to the designated area.

Feel free to message me with any questions and I'd be happy to assist however I can.

Best of luck,

Eric

I typically use Gardner S-100 on a flat roof and have had excellent results with it.  For a pitched roof I use Sta-Kool 780.

stephen
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Originally posted by @John Warren :

Hi all,

I have a fourplex with a six year old flat roof that is around 3600 square feet. There are a few spots where water is puddling, and it looks like it could use a protective coating rolled on. Does anyone have any advice on which coating to use? Home depot and Menards both carry multiple types of products, and since it is going to cost a good bit I want to make sure I get the right type!

GACO roof coating is a 100% silicone roof coating designed for flat roofs. It is the only coating that is recommended for ponding water. It is expensive but really good stuff.
I have used it in the past on a roof that had several leaks with great results.

Thanks for the tip on GACO. It is definitely not cheap, but the articles and reviews look fantastic. It looks like you just paint it on over the existing roof and you have a 40-50 year roof. That is pretty crazy!

I had a two-bedroom house in California that had a tar-and-gravel flat roof on about two-thirds of the building footprint. Water would pool up, as in your case. I was surprised that it didn't leak more than it did.

At one point I laboriously removed all that gravel, bucket by bucket down the ladder, and got somebody on craigslist to take it. Then I coated the roof with a Henry elastomeric coating, a white, rubbery, thick paint that can take some kind of filler underneath it to level the roof a bit. It wasn't worth the trouble. The coating would peel off in places, and it still leaked a little.

Finally my wife and I broke down and got a foam roof. It was _way_ better and provided some much-needed thermal insulation along with the waterproofing. If you can afford the spray-on foam, go for it.

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