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In the basement that I'm finishing I have an irregular, rough stone foundation wall, pretty dry. I'll use 1" XPS foam insulation, then drywall. Can I build the framing on the floor, attach the XPS to it directly, and then just raise the whole assembly snug against the foundation wall? Seems easier than attaching the XPS to the stone foundation.

Thanks for any insights here.

Jeff

  • Don't forget to fireblock and draftstop according to any local code requirements. Generally, you will need to add a break in the XPS every 10 feet or so (check local codes) and create a relatively air tight seal with the wall using a fire resistant material like pressure treated 2-by lumber. Also, most code references and recommended building practice I have seen call for an R value of at least 10 for basement walls which is generally a minimum of 2" of XPS--again I recommend double-checking local code. – statueuphemism Aug 27 '16 at 10:12
  • Thanks. For 10ft vertical fireblock, can I use a narrow 5/8" drywall piece, say at a vertical seam between sheets of the XPS? If so, is there any kind of caulking or spray foam that I can use to fill the little openings where the drywall fireblock meets the irregular surface of the stone wall? – Jeff Aug 28 '16 at 13:30
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That's how it's done, don't forget to apply chemical tape to the seams and seal the areas around the wall prior to installing it. You won't have another chance with out removing the wall first.

  • Thanks. So, do you know what kind of adhesive I use to attach the XPS to the back of the studs on the framing? – Jeff Jun 29 '16 at 13:05
  • Usually not adhesive. Washered (or "capped") nails. – isherwood Oct 27 '16 at 19:27
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I’ve had great success using PMF anchors to attach EPS or XPS to masonry and concrete. These work very well to allow for variance in the wall while ensuring a snug fit. Always apply a good seaming tape at the joints. Also, for protrusions or odd angles you need to work on, suggest you have some minimal expanding spray foam and foamboard glue on hand.

https://www.rodenhouse-inc.com/plasti-grip-pmf

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