Hello all, I have two questions. I’m currently planning a renovation of my basement. It’s currently unfinished, and we’re looking at finishing it to add living space. We intend to insulate the concrete walls with a layer of 2″ XPS and add a stud wall and fiberglass batts after that. So far, I’m reading that we shouldn’t add a vapor barrier on top of that. My question is this: if I can’t glue the XPS to the wall because mold loves glue, how do I attach the XPS to the wall before I get my stud wall up? Next question. I’m reading that a good way to prep the floors for covering is to put down a layer of 1″ XPS and then plywood on top of that. The load bearing elements are already in place downstairs (steel i-beams and posts). Should I put down the XPS and plywood before I put in the walls so that the walls are isolated from the concrete? If not, what’s the best way to isolate the stud walls from the concrete? I’d appreciate any insight.
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My opinion
I would attach the XPS to the walls with mechanical fasteners like Tapcon screws or powder-driven concrete nails.
When you talk about XPS on the floor, I assume you are talking about laying down pressure-treated sleepers first, filling in the spaces with XPS, and then installing the plywood. I would not run partition wall plates over the plywood, I would nail them to the concrete. They should be treated lumber. You may want to consider covering the entire floor with a monolithic layer of poly or some other vapor barrier before you do anything, and then install everything over that.
Best site for this question is Green Building Advisor (part of the FHB family).
Thanks for the response.
As far as the floor went, we're dealing with a concrete basement floor here, and I get the impression that concrete + wood = bad news. Not having ever dealt with this before, I assume the worst. We were planning on putting down the XPS directly on the concrete and plywood. The poly sounds like a good idea. The problem we're trying to prevent is the utter destruction of all our hard work should the basement ever have a wetness problem.
I'll check out the Green Building Advisor.
PT
I assume you are aware that you need to use pressure-treated lumber in contact with concrete, i.e. bottom plate of wall in basement.