23'x27' Flat membrane EPDM roof - practical questions

I plan to install a membrane on a 23’x27’ flat-roof. The roof has no slope, but shows only very minor pooling after a rainstorm. This surface will be used as a deck, so it needs to be walkable. There are no vents or protrusions, so it should be pretty simple.

From what I’ve read, .050-.090 reinforced fully adhered EPDM seems like the best choice for waterproofing. I’d like to install rubber pavers on top of the roof membrane surface, and may also install some GreenGrid green roof modules in the future.

One concern: Are the butyl adhesives used for joining the 10’ strips of EPDM reliable? Should I insist on a single sheet (no seams)? Are large (23’x27’) sheets of EPDM available and cost-effective? Are some brands better than others, or is EPDM just a commodity material?

Also, I plan to install wooden handrails around the perimeter of the roof. The style of the handrails will match those on our Victorian front porch. The handrail posts will need to be secured by screwing through the roof membrane. What is the best way to avoid compromising the membrane integrity at these points? I want this roof to last forever with no leaks…

Am trying to decide whether to DIY or hire a roofing contractor. I’d appreciate recommendations on suppliers of membrane for DIY work as well as roofing contractors experienced with EPDM (and willing to do a small residential job) in central Michigan…

Lots of questions there. Lets see if I can hit on a few of them for you.

  1. EPDM isn’t warranteed on a residential property.
  2. Your best bet would be to go with a .060 mil rubber. it comes in 10 or 20 ft sheets. any bigger than that and you are going to have wrinkle problems.
  3. rubber pavers is a great idea, I wish all of the homeowners would put them on their roofs.
  4. right now the “in” thing is tapes. A taped seam instead of a chemically welded seam. Taped seams are better!
  5. I would personally go with Firestone.
  6. You will not get a real secure handrail just by fastening them to the roof deck, you need to penetrate the roof deck and fasten the posts to the roof joists below the deck.
  7. the roofer will be able to flash the posts with no problems.
  8. I would hire a roofer to do the work, I would also hire a good carpenter to do the railing work…unless you can find both in one company.

Hope that answered some of your questions.

I would go with G tape…he is more reliable than splice adhesive. :slight_smile:

I agree with g-tape. I would also lookinto a tpo system as well. You can get it in an asortment of colors

I am very curious how you deck turn out? I am attempting a very similar project. Would like to know what you did for a deck and railing


Jim A

I used to install a lot of EPDM roofs back when I was an installer. First of all, I would not recommend EPDM for your deck. Instead, I would recommend a TPO if you want to go with a single-ply as the heat-welded seams will be better than glued or taped seams. As for the rest of your questions, g-tape pretty well covered them. I will say the posts should be flashed and counterflashed after being secured to the wood framing. It should also be noted that wood can wick water, so the posts should be painted or sealed really well to prevent moisture from entering the system through the wood as it ages and cracks.

As for whose product to use if you decide to stick with EPDM. First of all, I believe EPDM is now only manufactured by two companies, Carlisle and Firestone. I used to primarily install Carlisle as they were the leader in the rubber roofing industry, but anymore I think either manufacturer will be fine. I would certainly insist on a single sheet with no seams if you can get it, but it may cost you more since the roofing contractor likely will want to use remnants. If you can’t get a contractor to use one sheet, definitely try to limit the amount of seams installed on your roof. The rubber walkpads are a good idea to protect the roof from foot-traffic, but they will also help the roof retain moisture, which can lead to seam failure.

There is a lot more advice I could give you, but the best advice would be for you to hire a roofing contractor and not try to install a single-ply system as a DIY job.

5 ply ctp with double hard flashings and a double pour of rock to boot

I have only torn off the ctp, and the double pours can be hell on a cutter.

Have you checked into polyureas for your walkable deck waterproofing system?