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I'm planning to install an EPDM (Ethylene Propylene Diene Monomer) rubber roof on my 1922-built, poured concrete garage. The concrete deck leaks heavily during rainstorms, and it looks like installing an EPDM roof is just within my ability. One detail I'm unsure about is how to flash the edges of the roof deck, but I'd welcome feedback on any part of the plan.

Right now, the plan is to first install a layer of fiberboard onto the concrete deck. This is to allow good adhesion and provide some padding for the EPDM. I'm going to screw that down with 3" tapcons and special large washers designed for EPDM. Then I'll glue down the EPDM to the fiberboard, leaving a few inches of overhang on each side. (I'm planning to use a large enough EPDM sheet, 15'x20', that I can do the whole garage roof without any seams.) I'll then fasten the overhang to the vertical edge using a termination bar (basically a strip of aluminum with screw holes every 6" or so) along with some EPDM caulk.

This use of termination bars seems like it should be really reliable, but possibly overkill -- they're designed to help seal the EPDM on its way up a wall, and this is down. Another possibility might be to use aluminum roll flashing, but I'm not sure of how to best install that -- would I fasten it over the fiberboard and down the side, then glue EPDM over top? Or does the aluminum go on after the EPDM and if so, how do I fasten it without making holes that could leak through the EPDM? In either case, should I worry about ventilating anything -- is it possible for moisture to accumulate in the fiberboard?

Additionally, there is a gutter area shaped into the concrete at the rear of the garage, with a small pipe at its edge that leads to a downspout. I'm planning to continue using this to drain the roof, and expect to cut a small hole in the EPDM above it, flash that with EPDM flashing tape, and install some sort of leaf guard. I'd prefer to use a proper roof drain, but the pipe isn't wide enough -- maybe 2" diameter, slightly deformed metal.

Will this approach to flashing the edges and drain produce a long-lasting seal?

  • I just have a question if this actually worked?? We have the same problem with our concrete deck over a garage. Trying to figure out what will work? Thanks – Donna Coleman Apr 1 at 21:45
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Is the 2" diameter pipe (connected to the downspout) the only means for water to flow off the roof?

If yes, does this current system allow the roof to drain correctly? ie Does water flow off the roof in a reasonable manner or does it build up (puddling) or does it overflow else where off the roof?

I'll then fasten the overhang to the vertical edge using a termination bar (basically a strip of aluminum with screw holes every 6" or so) along with some EPDM caulk.

This use of termination bars seems like it should be really reliable, but possibly overkill -- they're designed to help seal the EPDM on its way up a wall, and this is down.

Also the above has me a little confused, is the EPDM being terminated via being dressed vertically up a wall or is it being bent down a wall (a photo of the existing would greatly help)?

  • So, it's been a few months and I have installed the rubber roof. Now to answer your questions. Yes, the downspout pipe is the only drainage. In a moderate rain it is sufficient but in heavier rains water runs off the back of the roof. This is not ideal but the back is well covered with rubber and there is a tree behind it, so it's acceptable. The EPDM is bent down on the edges of the roof, i.e. capping the roof with some overlap on the vertical surfaces. – Shimon Rura Jul 1 '11 at 19:46
  • @Shimon, good to hear you got the rubber roof installed. Would it be possible to amend your original question (or answer it) so that the community can learn from your experience? Thank you :) – Mike Perry Jul 2 '11 at 15:07

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