top of page



IDENTIFYING THE PROBLEM: The problem of wet basements is all too familiar to many homeowners. It is said that more than ninety-eight percent of all houses have had, or will have, basement leakage at some point. If you already own the home, no one has to tell you if you have a wet basement. However, if you are looking to purchase a home, you need to take the word of the owner if the basement has problems with wetness or not. So be a good detective and look for clues. One big clue is the presence of efflorescence, a whitish mineral deposit on the interior of foundation walls. This indicates moisture penetration. However, it should be noted that the severity of the problem is not indicated by the amount of efflorescence. Other clues are rusty nails in baseboards, rotted wood near floor level, rusted metal feet on the washer, dryer, or other appliances, mold and mildew, lifted floor tiles, storage on skids, peeling paint, and the presence of dehumidifiers.

CORRECTIVE ACTION: Poor surface drainage is one of the main causes of basement leaks. The ground should slope away from the house at a rate of one inch per foot for at least the first six feet. Seal where the driveway and sidewalk meet the foundation walls. The gutters and downspout systems must also perform properly. Downspouts that are disconnected, broken or clogged below ground level should be redirected to discharge above grade at least six feet away from the house. Gutters should be kept clear of debris. Interior low areas including basement stairwells, window wells, etc. may allow water to collect, so drains should be provided in the bottom of these. Where there are no drains, plastic dome covers over the window wells allow light into the basement while minimizing water and snow accumulation. In the vast majority of cases, basement leakage is not significant from a structural point of view. However, the presence of foundation cracks, damaged perimeter drainage tiles, a high water table or underground streams may call for more extreme corrective measures. These measures are used when chronic flooding occurs. Sealing foundation cracks can be performed several ways with the cost of repairs varying. The approach taken depends on the specific crack, with the most successful approach being sealing from the outside. Epoxy injection repairs can be done from the interior on poured concrete walls only. Excavating, damp-proofing, and installing drainage tiles should be used as a last resort. Damp-proofing on the exterior typically involves parging a masonry foundation wall with a one-quarter inch layer of mortar covered with a bituminous or plastic membrane which extends down to the footings. The drainage tile laid beside the footing is covered with gravel and filter paper. These tiles can often be damaged or clogged by roots, and some localized repairs may be required. Excavating on the exterior can be effective, but it is very expensive. An alternative is an interior drainage system which cost about one-third to one-quarter the cost of exterior work. There are many cases where this proves satisfactory, although this must be judged on a case by case basis. Where underground streams and/or a high water table are present, sump pumps are usually required.

Richard D. Malin & Associates: Technical Library

bottom of page