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EPDM directly to OSB

ckorto's picture

I'm doing another EPDM roof soon.  Been working with the material a lot lately and really like it.  Normally we install over Isoboard and when we don't I'll re-sheathe a flat roof with OSB.  I always put it smooth side up, figuring it was smoother and better for the adhesive to join to.  Anyway, tommorow I'm sheathing a new addition and normally put the sheathing rough side up according to boards stamp.  Here's my question:  Do I bother the inspector by asking if I can install the OSB rough side down or is it a big deal to install the EPDM over the rough side.  Any thoughts would be appreciated.


Sidenote-This is a tiny shed style back porch addition, nothing too fancy.  The budget allowed for either modified rubber or EPDM but no Isoboard so they went with the EPDM.

Edited 9/8/2009 10:22 pm ET by ckorto

(post #108866, reply #1 of 4)

If this area does not get high winds and there is no foot traffic on the roof, and you use the heavier.060 grade of EPDM, you should be fine glueing it to the rough side. I might use a double coat of the contact cement on the OSB - let the first dry well while you have lunch. Then do both again and roll it in.



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(post #108866, reply #3 of 4)

Thanks for posting, I appreciate it.

(post #108866, reply #2 of 4)

I've been told by the guys where I get my rubber (commercial roofing supply place) that the problem with glueing straight onto OSB is that when it is time to replace it, the OSB practically has to come up too.

We use a cover board made for the purpose. It is basically a fiberboard sheathing like Biltrite or the like. We screw it down with washer head screws made for the purpose.

I do think it would stick just fine to the rough side. At any rate,I think the rough side goes up because it is safer to walk on.

(post #108866, reply #4 of 4)

Osb can be installed either way. There isn't a top or bottom to it. Take pictures of the stamps on the roof if you are worried about him needing to see the stamp.

Is anybody out there?