Drywall, insulation, framing and basement.

Timothyv

Im not new to a saw. I have drywalled with family. Roofed. I can hit a nail with the first swing. Ok on to my post.

Basement - Going to frame the outer walls with 2x4's. Will frame out about 1 inch from the walls as most basements are not straight or square. As such I will have to put some insulation behind the 2x4's. Was thinking because I'm going to out on average, one inch, I would use R-20 as you would use this with 2x6 construction. Would this be a correct way of doing it?

On to drywall. Will keep the drywall off the floor about 3/4". As for vapor barrier.. I'm not sure what to do here. I've looked through all kinds of posts and some links posted here and I found that putting up poly will stop the concrete from breathing. Trapping moisture behind the drywall in the wood and insulation. I guess this would be moisture from the outside that might seep through the wall. I can see the poly being needed to keep the moisture from the air inside from getting to the cold concrete and producing frost in the winter then melting in spring and creating mold. Should I make sure that say at the bottom the drywall isnt super air tight to allow some "breathing" room. Or when I poly up the wall to leave the top unsealed to allow it to breath up there. And yes it gets cold here in the winter. (Northern Saskatchewan)

Thanks for any suggestions guys. Oh and I love this site.. learned alot here. Tim.

oh'mike

I don't put up a plastic vapor barrier over the foundation---I believe that the plastic would hold moisture and bread mold.

If you wish to add a bit of air behind the wall---cut in a couple of return air registers (on opposite ends of the wall)----cover with a magnetic sheet in the winter.----Mike---

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jklingel

A couple of thoughts. Fiberglass batts are poor insulation. Rock wool will work better. If you have an air gap behind a wall, you get convective loops which kills your insulating ability. Were it mine, I'd sheath the wall w/ rigid foam first, sealing/taping joints. No vapor barrier over concrete.

wwsteel7

the building code in Alberta for frost wall installation in basements requires 6 mil poly to be installed on wall, after the wall has been insulated, and joist ends insulated with the joist end poly being long enough to be draped over the top of the wall and be tied into the wall poly and sealed with tuck tape or caulking. If your joist end measures 12 inches by 19 inches, cut your piece of poly 24x24 so as to ensure that you can staple it easily and possibly tuck tape or caulk it to from a good seal.

Also, the "gap" at the top of the wall, (the 1 inch air space between the rim board/concrete and the wood/steel frost wall), must be insulated with either the joist end insulation piece, or a seperate strip.

To frame your walls 1 inch from the concrete correctly, you must measure 1 inch at the TOP of the wall. Taking your 1 inch measurement from the rim board at the top, installing your top track/plate first and then plumbing down your wall will ensure that your walls are square because it is the rim board that was squared-up by the framer/cribber. The concrete walls may differ here and there, but not the rim board.

jklingel

Wow. Does the code say "6 mil poly", or is that what people say it says? An inspector here told me several months ago that "We only accept 6 mil poly", till I asked him to read me the code. It really says "A vapor retarder of 1 perm or less." But, if the code says poly, then poly it is. That is contrary to current building science (generally), but wth?

Gary in WA

I know your Codes are different in Canada, wwsteel7. Wouldn't you have the option for interior foam board without the exterior below grade insulation? Here, at Fig.2:4, ; http://www.nrc-cnrc.gc.ca/eng/ibp/ir...199/part2.html

Figure 2:11 gives the option of strapping on concrete with foam board and drywall as the air barrier and fire-stopping.

Gary

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Timothyv

Well I see that I can go a few different ways here. Vapor retarder sounds like the right way to go with rigid foam. Wish I lived in a warmer climate.

Thanks for the ideas all. Tim.

Gary in WA

Be sure to check with your local B.D. for the final route, glad we could help...

Gary

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