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Attaching foam exterior concrete wall

10951 Views 7 Replies 4 Participants Last post by  rustyjames
I am getting ready to insulate the exterior of my 10" poured concrete basement walls with 2" XPS rigid Styrofoam. The wall will be waterproofed with Bituthene sheet membrane above and below grade. The Styrofoam will not only insulate but will also serve as the protection board for the Bituthene. The above grade portions of the wall will be stuccoed with synthetic stucco.

The below grade portions of the foam will be held in place by the backfill. The above grade portions must be adhere with fasteners. All of the literature I've read about stucco recommends using Tapcons w/ washers that will fit flush against the foam. However, my contractor has suggested using a Ramset w/ washers, which I'm sure would be much faster and easier since the holes would not have to be predrilled. However, I'm not convinced that easier is always better.

I'm concerned about:

1) will the ramset nail be sufficient to secure the foam in the concrete and hold the weight of the board w/ m/l 1/4" of stucco on it?

2) can you ramset into the foam without destroying the foam?

My gut feeling is to go with the Tapcons as recommended but I would appreciate your recommendations here.
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There are EIFS systems that are robust enough to deal with at grade issues such as stones, weed wackers, etc. There are also adhesives for gluing up the rigid foam. If it were me, I'd go with a few tapcons and washers too.
There's a lot of building's around with EFIS systems on them with the foam at grade, that's all I can say.
I should clarify that the XPS backed systems are much more durable than the EPS. I wouldn't use the latter at grade either.
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