Flat roof membrane: EPDM vs elastomeric
Hello all,
I have not found any information comparing EPDM to elastomeric membranes in the vast archives of GBA. I’m just wondering what people’s opinions are on the two. I’m in southern Quebec, CZ5, and this will be a vented flat roof (and I have read how to correctly vent a low sloped roof). My understanding is EPDM is taped whereas the elastomeric is sealed with heat (i.e. a blowtorch). Installers of both materials claim 20 to 30 years longevity. Seems one advantage of elastomeric is the top layer can be refinished to renew the roof whereas the single layer of EPDM would have to be pulled up and replaced. Pricing is similar enough between the two. Not sure if one could be considered more sustainable than the other…?
These are the recommended elastomeric layers by one installer:
https://www.soprema.ca/en/products-systems/soprafix-base-635
https://www.soprema.ca/en/products-systems/sopraflash-flam-stick
https://www.soprema.ca/en/products-systems/sopralene-flam-250-gr
Many thanks.
Shaun
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Replies
EPDM is glued down and the seams are sealed with sealant or sealant with tape. I don't have first-hand experience with torchdown--the industry name for what you describe--but I have heard from reliable sources that it's as good or better than EPDM in most regards, though there is danger of starting a fire.
My understanding is EPDM is the best most durable material, but the detailing of seams and penetrations is the potential weakness. For a simple roof that can follow all the standard manufacturer's details it can be great. I believe the alternate product you provided cutsheets for is a SBS modified bitumen roof (built-up roof), which can be a perfectly good roof and will have less issues with seams & penetrations. It can be applied torch-down, adhered, or partially hot-mopped. Depending on the spec. I would call a local manufacturer's rep to get a system recommendation from them based on your desired warranty.
Elastomeric is a fluid applied roofing or waterproofing. I've only used on commercial concrete decks/balconies.
I would not use torchdown or any other segmented. I have had good luck with EPDM, but there are other membrane roofs that others like
Agree, penetrations are the devil.
ShaunQC,
Have you checked with your home insurance people about the roof. Likely lots of changes in the years since your current roof was put on. Fire may not be a Quebec problem now, but insurers may see it differently.
EPDM can be installed by anyone so you get a wide range of skill and workmanship.
thermoplastic roofs [tpo, pvc, kee] need specialized equipment -- seams are machine-auto-welded. on the whole they are generally better installed than EPDM since the installers generally are better trained.
SBS modified are good roofs. on a wood deck, i would only suggest cold applied -- not torch down.
you can get EPDM or TPO with a declare label from ILF. I believe there is EPD information for SBS roofs too. I don't know the comparisons between them.
There are EPDM manufacturers who can supply single sheets large enough to cover your entire roof, i.e no seams "in the field" of the sheet. Conservation Technology is one that comes to mind. I'm sure there are others.
Size versus weight is a trade off. Carlisle Syntec makes a 50x200 roll. (Others too) At 1/2 pound per square foot you need 12 guys and a crane to install.
Yes, a sheet that size is heavy. But you've got to admit that it does solve a problem mentioned by ShaunQC, no seams. Anyhow, unless someone's building a warehouse they're not going to need a sheet 50x200.
When I did the back of my roof, I wanted an almost seamless roof, so we rough cut the sheet in the front yard, rolled it back up and maneuvered it up onto the deck. With only 8 feet to get up, we unrolled the sheet on the deck and rerolled it up on the roof, so we did not have to lift the roll up
It was only 20x~60 x.06 but still plenty heavy