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Old 09-07-2012, 11:38 AM   #1
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Basement Subfloor

I'm working on a basement renovation on a 1960's bungalow and I'm a little unsure of how to proceed with the subfloor. The basement was stripped to bare concrete last year. Through the winter I framed the exterior walls and had 4" of 2lb spray foam installed. I spaced the framing off of the concrete so that I could get 2+ inches of solid foam against the concrete and thus not require a vapor barrier.

Now I've come to the floor. I have waterproofed the exterior of the basement foundation, but the floor slab does not have a vapor barrier or insulation underneath. The floor previously had a mix of asbestos and vinyl/tar tiles on it in various areas. At some point a layer of poly was laid over the tiles and carpet installed. When demo'ing the carpet and poly, the tiles underneath had turned into a sticky goo from the high moisture for so many years, so there is definitely moisture moving up through the slab.

At this point I've removed the loose asbestos tiles and scraped up as much of the vinyl and tar tiles as possible. Where the asbestos tiles came up there's really not much adhesive left at all, mostly just bare concrete. The vinyl tiles have left a nice coating of tar on the concrete however.

My plan is to put down a layer of 1/2" XPS and 6mil VB on top of the remaining asbestos tiles and tar. Then lay 5/8" T&G ply on that and continue on with my flooring. I looked at both DryCor and Barricade, but I figure that my material cost for XPS and ply will be about 1/2 that of DryCor or Barricade. So the question is, am I ok to simply lay XPS on top of the remaining tiles and tar, or do I need to get back down to bare concrete before laying my foam? My goal is to get a decent VB on the floor along with some minimal insulation value just so that the floor isn't so cold on the feet.

I'm in Winnipeg Manitoba (~6,000 HDD) where we deal with quite a bit of cold weather. Having a nice warm basement floor will be great!

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Old 09-08-2012, 09:34 AM   #2
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If you put a thicker layer of XPS, the necessity for a vapor retarder goes away.

If the grading and moisture issues were there before, it is entirely likely that moisture may have gotten in a while ago and just been trapped there. Obviously it can't dry through plastic.

I would just go with the thicker XPS as it is more moisture friendly than EPS and be done with it.
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barricade , basement , drycor , insulation , xps

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