We bought a house a little over a year ago. The old carport had been converted into a den. It had musty, dirty carpet, so we ripped it out. A big problem we ran into is that we live in west Tennessee with high humidity. The room became unbearable to go into, and mildew began forming on the walls.

We've tried cleaning the walls with bleach, but the only thing that has worked is a dehumidifier. So progress on the room has been at a standstill, and we have no clue as to how to proceed. How can I seal this concrete so we can put flooring down and actually use this huge room?

  • Is the moisture rising through the floor, seeping through walls, or just from condensation? If it's a converted car port, I would check whether sufficient damp proofing was done as part of the conversion work. – Rowland Shaw Jan 31 '15 at 15:29

Other than taking a jackhammer to it and doing it right from the bottom up, (or turning it back into a carport):

Lay 6 mil plastic in a continuous sheet, place 1 or 2 inches of XPS rigid insulation sheets, pour 2" of gypsum cement (might as well place radiant floor heat tubing while you are at it, even if you don't have immediate plans to use that.)

A cement slab for a carport almost certainly has no waterproofing below it nor insulation of any kind.

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Try a tanking slurry product like KA tanking slurry , uselly used in basements, brushed onto the concrete floor. The correct method as previous poster mentioned would be to remove the concrete floor and install a proper dpm.

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