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I have built a 32-by-56-foot basement and covered 46 feet of it with a roof with a slope that rises 4 inches for every foot. The last 10 feet of the basement are covered with a 10-by-32-foot, 5-inch-thick concrete ceiling or slab, which will be used as a patio floor after we build our house on top of the basement.During the winter we have a condensation problem on the inside ceiling or the bottom of the slab. I have tried insulation on the inside, but it didn't help.

I left the insulation up for two weeks. When I removed it to check for water, there was a large amount of condensation on the bottom of the concrete. - S.M., Lenoir City, Tenn.

Answer - Cover the concrete with a 4- or 6-millimeter plastic vapor barrier. The barrier should be in one piece with no holes or seams. Fasten the vapor barrier at the perimeter with wood furring strips bolted or screwed to the concrete slab. If holes or tears should appear, cover the openings with duct tape.

Another solution would be to install a dehumidifier in the room under the slab.