Q: As we were renovating our 1920 Craftsman bungalow, the tarp covering on our roof blew off on an extremely windy day, and water poured in and collapsed some of the ceilings. Now we're wondering if the walls have been damaged as well, though they appear to be in good shape. Is there some way to check?

— Julie, Decatur, GA

A: Norm Abram replies: First things first: Is the roof back on? No sense in doing anything with the walls until everything's snug overhead. Assuming that's taken care of, you're right to be suspicious of the walls' appearance. Plaster can be dry on the surface and wet inside the wall cavities. To find out, drill some 1-inch-diameter holes through the plaster and lath and reach in with a finger, or maybe with a stiff wire to determine if the insulation or the back side of the wall is damp. If the inner surfaces feel dry, you should be okay. Just fill the holes with a patching plaster.

But if you do detect moisture, call in a firm that specializes in drying out water-damaged houses. They have giant fans and dehumidifiers to quickly lower the moisture content of wet interiors, as well as the instruments to measure progress, even inside walls. With any luck, they'll have everything down to a 10 percent moisture content in a few days. At that level, you eliminate any chance of mold taking hold on the plaster.

To find a company in your area that takes care of soggy houses, log onto www.iicrc.org, the Website for the Institute of Inspection, Cleaning and Restoration Certification.
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