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123pugsy 01-31-2013 06:40 PM

Basement Washoom
I'm renovating my basement washroom and found some loose fitting 1/2" styrafoam which I've already tossed out. There was no vapour barrier.

Should there be a vapour barrier used when it's against concrete block? I see no signs of mold in the wall at all and its been like that for about 25-30 years I'd guess.

Should I use some styrafoam pink agianst the blocks?

The wall on the right is a cold cellar. If I insulate the wall, should I use a vapour barrier there?


profcolli 02-02-2013 03:36 AM

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Based on what I've read if you use styrofoam you don't need a vapour barrier as it provides a thermal break. Loosely fitted is apparently useless - my structural engineer said that if it wasn't securely fastened (glued and mechanically attached with screws or studs to the concrete block) the styrofoam might as well be stacked in the middle of the room. Putting it in between studs would not be good on an exterior wall, not sure if that is a problem on an interior wall - but I am gutting everything anyway and redoing from scratch.

I put up 1" XPS on my internal basement bathroom wall but I see you have plumbing and furring strips in the way (hopefully that is not an exterior wall!). One advantage is that I can glue drywall right on it (with PL 300 foamboard glue) and secure with tapcon screws right into the cinder block. No need for further insulation nor vapour barrier (but I don't have plumbing on this wall - you would still need to use studs to accommodate yours).

123pugsy 02-02-2013 05:24 AM

Thanks profcolli.

No vapour barrier then.

I will use the PL to glue up foam between the furring strips and then use spray foam in all the gaps.

I will have to insulate/spray foam all the drain/vent lines to keep them from sweating.

The drain and vents are staying. I will re-route the supply lines to the other walls.

profcolli 02-02-2013 02:44 PM

Better to remove the furring strips and put them back after the foamboard is up (especially if you are moving the supply lines). Hard to tell from the pic but you may have room to slip them behind.

PL 300 foamboard glue - regular PL will burn the foam. 1/4 inch expansion gap for the perimeter, filled with low expansion foam, tuck tape (tyvek tape in US) for the foamboard seams - that is how I am doing it (straight out of the Mike Holmes book).

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