What's proper EPDM underlayment and detailing

On a 12/12 what’s the correct underlayment? Can I hand pick from my CDX and touch up surface defects with durabond or use 1/2" plugged and sanded ply? Fill nail holes too? How tight does the seam in a valley need to be or will we be laying a smoothing tape down the valley first? On my rake drip edge how’s it finished? I’ll have one 2’ seam. How difficult would doubling the 60 mil be using the black glue once I have my template made?

You need to check the specs for whatever specific manufacturer you’re using but here are some quick answers-
I like iso underlayment, attached with plates and screws. then you don’t need to worry about nail holes, although you can attach directly to plywood and I don’t think nail holes are an issue. Valley and other seams need to be pretty tight, but I would install Reinforcing strip over it to help bridge the transition. I usually finish both my rakes and eaves by running epdm long over the edge, installing drip over top, prime and tape. Its quickest and effective.

But there are many details.

Thanks, what’s ISO? I would be using black Carlisle and yellow gluing direct to the CDX. The “Reinforcing strip” is a tape or plate? I see that theres a white EPDM now too: bestmaterials.com/detail.aspx?ID=15884

White was a disaster for epdm at one time I thought.

polyisocyanurate insulation, google it.
Russ strip is basically an additional adhering method, besides your glue. It prevents the rubber from lifting off of the substrate in transition areas, like roof to wall or other penetration, and valleys. You may not need it, depends on the application.
What you really need to do is go to carlisle’s website and look at all their detail drawings. I’m sure donl can help you locate it, pm him.

Also with EPDM roofing membrane, make sure it does not come in contact with any old cap sheet. EPDM will break down when exposed to asphalt products.


JW Roofing Miami - Weston Roofing

Thanks for the tips. I’m familiar with the ISO but only as an insulating board I’d strap and drywall over though you see massive quantities on ebay from large commercial jobs which must spec for complete replacement when installing a new membrane. I thought you had an acronym for some newfangled membrane by ISO