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.