Author Topic: EPDM, cured or uncured, which is sticky?  (Read 717 times)

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Offline Michael Kellough

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EPDM, cured or uncured, which is sticky?
« on: September 19, 2020, 03:11 PM »
Putting a deck on a low slope roof (2” over 8’). To minimize penetrations through pvc roofing I’m screwing square aluminum tubes to the roof then building the deck on top of the aluminum.

I’ll use neoprene washer head screws (with a dab of silicone on top of the fastener) to seal above the aluminum but I think I should put something sticky under the aluminum to stop water that would creep under the tube.

Some kind of EPDM or something else?

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Online Cheese

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Re: EPDM, cured or uncured, which is sticky?
« Reply #1 on: September 19, 2020, 04:58 PM »
Michael, I’d use an EPDM flashing tape. It comes in 4” widths. Cut a roll in half.

Offline Peter Halle

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Re: EPDM, cured or uncured, which is sticky?
« Reply #2 on: September 19, 2020, 05:52 PM »
I very possibly could be wrong, but somewhere in the back of my mind I seem to recall that edpm and pvc are not happy together.  Edam flashing is uncured and more flexible than cured.

If you know the manufacturer of the roofing system you might want to reach out to their technical support people.

Is there a way to achieve your goal without fastening into the existing roof and have the decking system floating on top?  That is what I have done with building decks on top of edpm roofs.

Respectfully,

Peter

Offline Peter Halle

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Re: EPDM, cured or uncured, which is sticky?
« Reply #3 on: September 19, 2020, 07:13 PM »
I forgot to answer your original question.  If you can use edam, there is adhesive backed uncured flashing.  When I have done roofing / decking projects with edpm the fishing costs have almost equaled the roofing costs on a 14 x 20 deck.  Be sitting down when you check the prices.

Peter

Offline Michael Kellough

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Re: EPDM, cured or uncured, which is sticky?
« Reply #4 on: September 19, 2020, 07:51 PM »
Floating deck? Thanks for bringing that up.

It’s only 100 sq ft and original plan was wood decking. Thought that might be susceptible to wind but now the decking is composite and substantially heavier than wood. I’ll give floating some more thought. Maybe the aluminum tube can be captured by strips of pvc welded to the glued down pvc roofing.

Original deck/roof was just roll mineral-asphalt, nailed, and the pitch was less. 2x4 sleepers bedded in tar and nailed (redi-made goo in a pail which also covered roofing nails). Sounds horrible but didn’t leak for 25 years. Replacement should last quite a bit longer, especially if the deck floats.

Offline Michael Kellough

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Re: EPDM, cured or uncured, which is sticky?
« Reply #5 on: September 19, 2020, 09:23 PM »
Probably just drill some holes in the bottom of the tubes and bed them in urethane adhesive.

Offline Peter Halle

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Re: EPDM, cured or uncured, which is sticky?
« Reply #6 on: September 19, 2020, 09:23 PM »
If it works for you, you could basically build a “pallet” with pressure treated sleepers and then composite decking on top.  In the most perfect world you would place a piece of the material underneath each sleeper to eliminate friction and any chemical reactions with the important thing - the roof.

Local conditions might influence your particular situation but a ten x ten deck won’t blow off except for a storm of a magnatutide.

P.s.  in designing your deck pay attention to the ultimate height and any possible interference with doors leading out to the deck.  Especially if their are out swing screen or storm doors.  Also deck fastening system screw lengths.

Just offering some thoughts.

Peter

Online Cheese

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Re: EPDM, cured or uncured, which is sticky?
« Reply #7 on: September 19, 2020, 10:38 PM »
I very possibly could be wrong, but somewhere in the back of my mind I seem to recall that edpm and pvc are not happy together. 

I don't know Peter...but both EPDM & PVC are very inert materials, they've both been used as washers/separators when fastening aluminum bumpers to automobiles using steel bolts. That slows down or can even mitigate the galvanic corrosion that is produced when the two dissimilar materials are subjected to a salt/water environment.

Unless they're both in solution, I'd expect there would be no issues if layering the 2 materials against each other.

I do know this however, after considering installing a Koi pond several years ago, I checked into whether I should install a PVC or an EPDM pond liner. The consensus was that the PVC liner would last for 10-15 years while the EPDM liner would last for 40-50 years. 
 [2cents]

Being subjected to all day UV on the top of a roof, I'd hedge my bets on the EPDM for a long term solution. It has been the standard for the construction industry for last 80+ years.
« Last Edit: September 19, 2020, 11:09 PM by Cheese »