Sealant for XPS Sheathing
My next step in my project is to apply a bead of sealant throughout the inside stud bays where the exterior foam sheathing (reclaimed and clean xps) meets the framing material. A while back I tried a caulking product that was specifically formulated for foam, but discovered that after it cured it very easily pulled away. It had little adhesive characteristics.
I’ve used both Great Stuff Pro Gaps and Cracks, and their Construction Adhesive foam and found that both products adhere to the foam and wood very well.
My concern is that, although the Great Stuff foam adheres well, is flexibility a characteristic I should be looking for in a product?
Alternatively, I could use Loctite Pl Polyurethane caulk, which is flexible and in my experience adheres amazingly well to anything it comes in contact with.
The foam is very easy and quick to apply, as well as economical, but would appreciate input and suggestions.
Thanks, Daniel
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Replies
I've used PL300 with XPS before and had no problems. It takes a while to fully cure is all, but it does a good job. The cured material is not flexible though, it cures to a pretty rigid consistancy similar to what the regular liquid nails product cures to.
Don't try to use Great Stuff as an adhesive. Yes, it's sticky, but the expanding property will push stuff apart and cause problems. I tried that once, it didn't work well and caused me a lot of extra work and I don't recommend doing it that way.
I haven't tried using polyurethane caulk on XPS. As long as it doesn't eat the XPS, it's probably OK. I'd do a test first and see what happens. If the caulk causes the XPS to dissolve or otherwise change into something else, then don't use that caulk with XPS.
Bill
PL300 was the sealant I found didn't adhere well to the xps. Even after several weeks it easily peeled away.
I should better describe, the xps sheathing is fastened to the frame exterior with 1x4 strapping at every stud that are screwed to the studs with Fastenmaster Windlok screws. I don't believe it's likely that a foam bead spayed at each inside corner of the intersection of the xps sheet and stud, and which can readily expand into the studbay, will push the xps sheathing away from the stud. Great stuff Pro constrution adhesive doesn't expand nearly as much as gaps and cracks either.
The canned foam holds tenaciously to the xps and wood, but I'm not sure how much movement it can sustain. It certainly is a much faster and economical approach.