How to Frame a Basement Wall to Keep Dampness Out

LESLIE: Larry in Schenectady, New York is finishing the basement and needs help with a project. What can we do for you?

LARRY: Hello, I love your show. You guys do a great job.

TOM: Thanks, Larry.

LESLIE: Thanks, Larry.

LARRY: What I’m doing is I’m – I have started framing out my basement with 2x4s and r13 insulation in between the 2x4s.

TOM: (overlapping voices) OK.

LARRY: But I’m wondering if I need to treat the walls with any kind of a vapor barrier. Or is it OK if I just leave the walls a couple inches away from the actual concrete block?

TOM: Yeah, good; that’s the right thing to do. You want to leave some space. You know, I don’t think it’s a bad idea to use a so-called damp-proofing paint because what it’ll do is it’ll stop some of the evaporation of moisture in the wall. Because the concrete block is very hydroscopic, it’s very absorbent and you will get some degree of moisture that wants to sort of draw into that; it can evaporate into the basement. So putting a layer of the damp-proofing paint on the inside of that block wall is not a bad idea. Now that’s not going to stop a flood; if you have bad drainage outside, the water will still get through. But for the most part, it’ll stop some of that sort of surface transfer of humidity into the basement.

Building the wall a few inches away – you know, maybe a hand-width away from the wall so you have some air between the block wall and the frame wall – is a good idea. I hope you’re using pressure-treated studs or metal studs, because you don’t want to use – I mean for the sill plate, at least; pressure-treated sill plate or metal studs for the whole thing.

And then the last thing is that when you get done with the wall, put a couple of fake vents in it – couple up high, couple down low – to let some air sort of circulate behind that wall back and forth.

LESLIE: To keep things dry.

TOM: It can look like a heating duct but it’s not really a heating duct. It’ll circulate some air behind the wall; keep it nice and dry.

LARRY: Oh, OK. Great. Thank you very much.

TOM: You’re welcome, Larry. Thanks so much for calling us at 1-888-MONEY-PIT.