We're planning to carpet the basement in our 100-year-old house, which presently has a painted concrete floor. The floor happens to be quite uneven and seems to have been designed to channel water into a now-plugged drain. No water issues in the basement since we've lived here, so this appears to be an obsolete feature due to likely corrected basement water problems.

Several contractors visited and told us that all we need to do is lay down the carpet and padding on top of a vapor barrier, skipping subfloor construction. They said they'd even out (but not level) the flooring by using a form of leveling compound.

I'm not particularly concerned about the "cold floor" issue, but I am of course concerned about the possibility of moisture buildup leading to mold or musty smells. It's certainly appealing to skip the whole subfloor given that it would save the need to level the floor, save money, and we'd retain important headroom.

However, I'm concerned about the moisture implications. A couple of the contractors seemed confident that the painted floor stops moisture from rising through. If it's as simple as just painting the floor, why do I read about so many people recommending insulation and a full subfloor?

  • Hi Glenviewjeff, could you let us know how long you've lived in this house? Also is a subfloor a comfortable option (do you have the ceiling height to work with?) or is it solely cost that is the concern? – Chris Aug 18 '16 at 15:16
  • We've lived here a year. Subfloor will raise height substantially because we'd have to flatten the floor on top of the added thickness. The ceiling height isn't great as it is, and I would be pretty unhappy losing another six to eight inches as would likely be the case. – glenviewjeff Aug 18 '16 at 15:27
  • Have you tried taping some clear plastic down to the floor for a few days? This will show if moisture is making its way through. On some floors that just "Sweat" a good epoxy paint properly installed can seal quite well. many times with older homes the walls also leak. It is possible exterior foundation drains were added after the house was built. – Ed Beal Aug 18 '16 at 18:41
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    I think it is guaranteed you will have musty smells and condensation unless you put insulation between the concrete and the carpet. I'm not a contractor, but every single basement I have seen where they carpeted over concrete was musty. It is strictly a matter of temperature change, not seepage or vapor. The cool concrete causes condensation of water vapor on the air. You could level, then glue down 1/2" foam insulation sheets, then glue plywood on top of that. It will be plenty strong, and condensation free. Probably not code though. – mkeith Aug 22 '16 at 4:42
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    I would level out the low spots and go carpet shopping. A good quality pad acts as insulation and feels better to me. Just keep an eye open in the winter for leaks and you should be good to go. – Ed Beal Aug 29 '16 at 18:50

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