DIY EPDM job..... what went wrong

We’re building a giant playhouse in the backyard and after a ton of research decided to use epdm on the deck. It looked really good once we were done but after the first few months, giant wrinkles developed. What did we do wrong? We used water based adhesive (Lucas 8800) to glue the epdm onto 3/4 ply. Drip edge was nailed to the deck edge and covered with cover tape. The wrinkles got bigger and bigger as time went on.
How can I fix this mess and keep it from happening again on future projects?

Was it cold out when you did this like 45 F.

Did you let the sheet lie in place for a while (1/2 hr) before bonding it.

You said you used water based adhesive can you recall the rate at which it was applied, how thick was it.

Did you pull on the EPDM sheet to make it fit or to get it in place, if so how long did it sit before it got bonded.

EPDM is not a DIY project

Are there any bubbles that aren’t close to a post? I’m wondering there are minor leaks around the posts causing the bubbles.

Epdm was laid last year in March in 70 degrees weather. (Houston area) the wrinkles didn’t form until the summer months once it got up into the 90s.
Yes we had the pieces laying out for at least an hour before applying the glue.
I remember it being a cloudy day though. Does epdm need direct sunshine to stretch out?
Were we supposed to stretch it out manuelly or just let it lay out?

The adhesive was applied with a 3/8 nap roller and then we waited till it turned clear.

The wrinkles are only close to the posts. No leaks as far as I can tell. I still have access to the plywood from the underside and don’t see any leaking or water damage (yet)
As I said, everything looked perfect for at least a couple months until the temperature and humidity went up. Makes me wonder if epdm can only be applied during the hottest month of the year but surely that can’t be the case?!

It’s looks like you did a decent job, perhaps moisture is getting in through the posts.

Was the plywood treated lumber?

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Yes the plywood was treated. Was that good or bad?

Treated isn’t the optimal deck to use because of the possibility of it being wet and gassing, or some shrinking. If the post are, through and through, you could also have some movement of the structure.
You do have an option. Pop a line out from the post about 12-16". Cut the EPDM. Do a field seam with 3" seam tape. The seam will be against the flow direction, but seal the edge with some black caulk sealant. This Will give a look at what the problem is. Treated post are a pain because flash tape " don’t like em". Use some water cut off, under that tape at the post


You have created a water trap at the posts. Any cracks at the wood or water that soaks into the wood will soak down the post into the roof. Nothing you can really do about it at this point unless you wrap the posts from top to bottom in EPDM.

Water based bonding doesn’t really off gas much like solvent based bonding. The most likely cause is simply installation error. If you had a small wrinkle or raised spot against the edge which you tried to work out it may have looked fine when you finished, but sometimes they can re-appear in the heat since rubber expands and contracts.

The EPDM is still water tight where wrinkled and won’t really effect anything. If this was a warranted job they would need fixed but for this case it isn’t necessary. Unless you are worried about someone tripping over it there is no need to try to fix them. If you do want to fix them you just need some 6" seam tape and a piece of rubber cut slightly less than the width of the seam tape, you will then prime and stick the strip of rubber to the seam tape so a 1/8-1/4 of seam tape is exposed on all 4 sides, this is called a slider. Slice the wrinkle so it lays flat, brush some bonding under so it sticks to the deck, and then set the seam tape with the rubber on top over the cut, clean with membrane cleaner, don’t use soap, and prime the EPDM first, then let it tack before setting the slider in place and rolling with a hard roller. When you roll start from the middle and work to the outside edge.

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EPDM makes a great roof, but not such a good deck surface unless it gets covered by something. It’s too prone to tears. You can’t put tables or chairs directly on it. It’s also miserably hot to walk on barefoot. When we’re installing it on really hot days sometimes it’s too hot to kneel on or even hold in your hands. As for your job here, you can see a crack in the second post where water is surely seeping in. Probably happening around all the posts. Out of curiousity, why did you need to cover the deck? Was it not a regular deck? Maybe it also forms the roof of something underneath?

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Normally I only give advice that I would recommend to a customer as a permanent solution but in this case…Beings it is a playhouses and it is not leaking, I would find some rubber patio pavers, lay them On top and you won’t see the wrinkles.

Also not a big fan of wrapping any type of roofing around wood posts, it will eventually leak no matter what. I would slide some pvc or composite post sleeves with caps over the posts to act as counter flashings.


We chose EPDM because we get a lot of rain and wanted the kids to at least be able to use the bottom wrap around porch without getting rained on from the top deck.

The plan was to cover the posts with composite sleeves and put sleeper boards and composite decking on top of the EPDM. Babies got in the way and we just never got around to it though. I didn’t realize waiting too long would become an issue :woman_facepalming:

I’m not concerned about how the wrinkles look but water pools around them for days and I can see the lap sealant around the posts starting to deteriorate from all that standing water. Therefore I’d rather get it fixed now before installing the deck boards.

So y’all agree that doing a splice would be my best option then? I was debating tearing the EPDM back off (at least the front portion) and starting over but I assume once it sticks it’s there to stay and won’t come back off?

If you used primer when you flashed the poles the lap caulk is unnecessary.

You can leave as is and install the deck boards.