|  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.
Corrective
Action:
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
occurs.
Sealing
foundation cracks can be performed several ways with the cost
of repairs varying. The approach taken depends on the specific
crack; however, the most 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 Carson Dunlop's The Home Reference Book
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