Leaky basement was masked by fresh paint

Q. We bought our home about a year ago, and no one disclosed the water seepage in the basement. The concrete walls were freshly painted when we were in escrow, but now the paint has bubbled, and there appears to be some kind of white, powdery mold. We hired a contractor who specializes in waterproofing, and he said the waterproof membrane on the outside of the foundation walls had failed. The sellers never said a word about this in their disclosure statement. What do you think about the lack of disclosure, and how can we fix this problem?

A. Leaky basement walls are common, usually due to faulty ground drainage and inadequate waterproofing of the foundation walls. Unfortunately, correction can be costly and intrusive because the excavation of the exterior is necessary to waterproof the foundation walls. The white, powdery substance, however, is probably not mold. What you describe is probably efflorescence, mineral salts that form on concrete and masonry walls where there is slow groundwater seepage.

Sellers in most states are required to disclose all known property defects to buyers. Masking a moisture problem with fresh paint is therefore a violation of that requirement. You should notify them of your discovery immediately and request that they pay the cost of remediation. Hopefully they will be willing to cooperate. If you had a home inspection when you were in escrow, your inspector may have been unable to identify the problem because of the fresh paint.

Hopefully, the costs for drainage remediation will not be excessive. To evaluate the ground drainage conditions around your home and determine what is needed to correct the problem, a licensed geotechnical engineer should be consulted.

Ground drainage improvement might include installation of a French drain around the building. This is a trench that is lined with drainage cloth, in which a perforated drainpipe and rocks are installed. However, it may also be necessary to excavate the walls to enable installation of an adequate waterproof membrane, depending on the severity of the water intrusion. Ground surfaces should be sloped away from the foundation, downspouts from the roof gutters should drain away from the building, and landscape irrigation near the building should be minimized. Finally, it is advisable to apply a waterproof coating on the interior surfaces on the basement walls. The most commonly used product for this purpose is Drylok, but a more effective coating material is Xypex. These are usually available at hardware and paint stores.

Q. We have a gas-log fireplace in our living room. The mantel is made of painted wood. Whenever we light the fireplace, the underside of the mantel becomes very hot. Is this a design flaw and if so, is it a fire hazard? What can we do to remedy this situation?

A. If the mantle is becoming hot, the fixture may be malfunctioning, or it may be improperly installed with regard to clearances from combustible materials. You should hire a qualified gas fireplace specialist to evaluate these conditions. And do not use the fireplace until you have had it inspected.

• To write to Barry Stone, visit him on the web at www.housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

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