The words are 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.
Identifying the Problem:
The presence of efflorescence, a whitish mineral deposit on the interior of
foundation walls, indicates moisture penetration. It should be noted that the
severity of the problem, or whether the problem is active, is not indicated
by the amount of efflorescence. Other clues are rusty nails in baseboards,
rotted wood near floor level, rusted metal feet on appliances, mould and mildew,
lifted floor tiles, storage on skids, peeling paint and the presence of dehumidifiers.
Poor surface drainage is one of the main causes of basement leaks. The ground
should slope away from the house a rate of one inch per foot for at least
the first six feet. As a preventative measure, seal where the driveway and
sidewalk meet the foundation walls. The eavestroughing and downspout systems
must also perform properly. If downspouts are ever suspected of being disconnected,
broken or clogged below ground level, they should be redirected to discharge
above grade at least six feet away from the house. Also, eavestroughs should
be kept clear of debris.
Localized low areas including basement stairwells, window wells, et cetera,
may allow water to collect. 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.
More Extreme Measures:
In the vast majority of cases, basement leakage is not significant from a
structural point of view and can be controlled relatively inexpensively, as
discussed above. 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
Sealing foundation cracks can be performed several ways with the cost of
repairs varying. The approach taken depends on the specific crack; however,
successful approach is sealing from the outside (Cost $500 - $900). Urethane
or epoxy injection repairs can be done from the interior on poured concrete
walls only (cost $400 - $600).
Excavating, dampproofing and installing drainage tiles should be used as a
last resort. Dampproofing 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.
Because excavating on the exterior is expensive ($8,000 - $15,000 typically),
an alternative is an interior drainage system. The cost of this approach is
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.
Line drawings are from the Carson Dunlop Home Inspection Training Program and
Home Inspection Software Tool - Horizon