No insulation behind drywall?

bert76September 4, 2009

Sorry in advance of this lengthy message, but I know you guys will have some thoughts on our situation.

We have been planning to repaint our basement walls after we stripped the awful plaid wallpaper down from the drywall. In doing some drywall exploration, it seems like there's no insulation between the studs on the exterior walls. While I know this isn't ideal from an energy standpoint, is it bad from a moisture standpoint? Or would it be OK since there's plenty of room for air to circulate between the studs? I have no idea if the concrete walls were sealed or not.

The husband is reluctant to let me cut out a hole in the drywall and do a moisture test by sealing some plastic over the walls. He justs wants to paint and be done with it without causing extra drywall repairs.

Last winter (our first in the 35-year-old house), the basement was quite warm, but I am concerned about what might be growing on the back of the drywall. We live in the Midwest, so we have extreme temperature and moisture changes throughout the year.

The basement does have a rather musty smell spring to fall (we do run a dehumidifier), but we also have old carpeting with thick padding on the floor that eventually will come out after painting. I'm hoping that removing the carpet and pad will help with the smell.

Once we figure out the drywall, we'll need to figure out flooring. I did put some sealed plastic down this morning so see if the floor is seeping moisture, but the concrete has old black adhesive that I have no idea how to handle.

Could we just lay down a moisture barrier sheet before putting commercial carpet down? Or would the moisture cause mold between the concrete and the vapor barrier?

While we would love the kind of budget that would allow us to rip everything out and do it again properly, that's not our reality. We have four young kids and really just need a nice, safe, inexpensive place for them to play in basement.



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If you're not using stone or ceramic, here are three sound choices for the subflooring. 1) Delta FL or equivalent followed by plywood or OSB. 2) Dricore or equivalent; 3) XPS (or EPS) followed by ply or OSB. The finished floor goes on top. Spring to fall, run a dehumidifier and check relative humidity levels if you're not sure of how dry "dry" is. Keep the windows closed.

When your budget permits, remove the drywall and start over with EPS, XPS or foam on the walls. No fibrous insulation or vapour barriers in the basement walls!

    Bookmark   September 4, 2009 at 5:42PM
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Thanks for the input.

I failed to mention that we have ceiling height issues, so I dread the idea of adding a lot of flooring materials even though I know it's the 'right' way to do it. Plus, I suspect that all of those flooring options are way beyond our puny DIY budget, which is basically enough for oops paint and closeout carpet tiles or something similar. I really need to know a cheap way to make the floor comfortable enough for kids to play on and not have the space smell musty.

So for now, we're OK with uninsulated walls?

    Bookmark   September 4, 2009 at 7:56PM
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I've used commercial low-pile carpets with no rubber backing on homes I've built myself, which have basement slabs of six inches of gravel followed by four inches of concrete. I'd be leery of using carpet on anything less than that. Why not just paint the concrete and use non-rubber backed throw rugs that you move often?

OK with uninsulated walls? Not much choice, you say. Be sure though to keep the dehumidifier going.

    Bookmark   September 4, 2009 at 9:14PM
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could she have that fiberous stuff blown into the walls...I think the only make 1" holes and sometimes can do it behind horizontal running baseboard molding so no repair is needed....or is that stuff not good against concrete..?

    Bookmark   September 5, 2009 at 9:42AM
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Worthy: Why no rubber backing on the commercial carpet? Does rubber hold moisture? (please excuse my ignorance :) One of the big box stores had the lowgrade carpet with white padding for 66 cents. I like the idea of a little bit of cushion for the kids, but only if it doesn't hold moisture.

I would paint the concrete, but we have that old black adhesive from a long-ago-removed tile to worry about. The lady at the big box store said it probably contains asbestos. I'm guessing that I can't just paint over that. Or maybe I can?? The surface would be very mottled with the adhesive and then the pits from removing the carpet tack strips along the edges. But maybe that would look cool? Would the paint seal the concrete or would the moisture cause it to flake off?

    Bookmark   September 5, 2009 at 11:58AM
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Pressure differentials, capillary action and (depending on the construction) drying pushes water vapour upward into the basement. When you put an impermeable finish on the floor, it traps the vapour, which becomes water, which nourishes the mould.

Yes, mastic before the late '70s contained asbestos. It can be removed safely by following the guidelines (follow link at Question 2) suggested by the Resilient Flooring Institute. Don't just scrape or sand it. The adhesive can also be safely encapsulated.

Here is a link that might be useful: Asbestos Abatement

    Bookmark   September 5, 2009 at 8:47PM
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Small update: I did a 48-hour test of two sealed plastic squares over different parts of the basement concrete floor. We even had a good rain storm on the first day. No condensation on either side of the plastic!

My theory that the musty smell is mostly trapped in the old pad and carpet seems more reasonable since we've never seen/felt any water in the finished area (and the unfinished area is where the sump is, which doesn't go off but in very torrential rains). The previous owners did have several dogs, which I suspect contributes to the smell. And we had a bathroom sink overflow last winter. I thought we ripped out all of the wet carpet, but it may have seeped further into the pad than what we ripped out.

I'm hoping all of this bodes well for putting down carpet (without pad) after we paint the walls and then rip out the rest of the carpet and pad. I've read that olefin is the best fiber for basements and to make sure the backing is also olefin and not jute. Does that sound reasonable?

Worthy: Thanks for the link. I printed it out and looked it over, but I can't seem to find anything about encapsulating it. I'm wondering if I even need to worry about the adhesive if we do carpet because the residue is rather thin at this point (maybe somebody scraped it in the past?). The lady at Home Depot said she just carpeted over her old adhesive.

    Bookmark   September 6, 2009 at 12:59PM
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It sounds like your basement is a good candidate for carpeting without pads. For the best prices, check out the small carpet stores specialising in odds and ends.

Encapsulating is mentioned in the Asbestos Abatement link.

The Fortress Institute says you can encapsulate with a concrete water sealer or latex based paint. Sprayed is preferable, as it doesn't disturb the mastic.

(I hate to think of all the asbestos fibers my friends and I breathed over the years either doing the demolition or working in the gutted homes later. I remember one woman renovator who had an entire first floor of mastic sanded off hardwood. In some places it was an inch thick. I guess the floor guy got the worst of that.)

    Bookmark   September 6, 2009 at 10:24PM
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I just helped my sister finish part of her basement. We put in Delta FL + OSB. It ran about $1/sq ft for materials and raised the floor about an inch. HTH in your decision.

    Bookmark   September 13, 2009 at 10:49PM
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