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dsbutler71 09-03-2007 08:04 AM

Concrete Flat Roof - Ponding
My garage has a concrete flat roof that was used by the previous owner as a roof deck (has a railing all the way around it). When it rains a significant amount of water ponds on the roof, up to 2 inches in the middle. Is there a type of light weight filler I can use to level it out? Is there any hope to fix it without replacing the roof?

AaronB 09-03-2007 10:04 AM

I would consider Spray Polyurethane Foam (SPF) for this application. It will last indefinitely if properly maintained.

the roofing god 09-04-2007 10:58 PM

or install a drain at the center if the layout underneath allows??--aaron right about the SPF for this though:yes:

dsbutler71 09-07-2007 10:01 PM

I think the roof would allow for a drain if the hole is around 3-4" in diameter. I assume that would be a lot cheaper than SPF. Is this something I can do myself? Could I use a hammer drill? Can I get a drain at Home Depot or Lowe's? The pipe from the drain is something I can handle, but I'm a little nervous about putting a hole in my roof.

Any idea how much it would cost if I had a professional install the drain? (assuming 20' of pipe and another whole through the brick wall).

the roofing god 09-07-2007 11:01 PM

YOU WOULD BE BETTER W/ A hITACHI sds DRLL and bit to drill the perimeter,then air chisel it through,the drain you would get from a roofing supplier like abc,allied,or bradco,etc-the abs pipe and elbows you could get at the home centers if you want

lynasm 02-04-2008 06:29 PM

same problem I have - ponding on flat roof
My garage also has an open deck outside the sun-screened room built above and everytime it rains (unpredictable in Houston Texas) I have to vac pump about 20-30gallons. The low area is right outside the sunroom where you'd step out. There is a drain somewhere underneath between the deck and the garage ceiling, the previous roofer covered it and sealed with gravel-covered rubber-looking sheath.
The same issue with the roof on which the AC units are affixed, standing water in the surrounding area. The same material (tar or rubber gravel), I think. Can you recommend what is the best way to avoid vac pumping every single time and to prevent roof leak?
Your advise is apreciated.


the roofing god 02-04-2008 07:45 PM

I could only suggest you repitch the cement floor so the water goes to the drain area-cement is not my area of expertise

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