Water,
Water Everywhere; Mostly In The Basement:
Wet basements the words are all too familiar to
many beleaguered homeowners. In fact the most
common single home maintenance problem in areas
with poorly draining soils is probably the
recurring wet basement.
The principal reason for the huge incidence of
the problem lies in the type of soil found
surrounding the houses. The soil that causes
problems tends to be a clay soil, with extremely
small particle size. Rainfall and roof runoff
water penetrate slowly through such soil. In
time, such soil becomes saturated and is often
unable to absorb more water when there is
additional rainfall.
Homeowners should be able to distinguish between
surface water, rising ground water and spring
water. Surface water comes from rain directly on
the ground around the house or from hillside or
roof runoff. Rising ground water refers to the
swelling of an aquifer an underground layer of
water beneath the house. Spring water originates
at an aquifer and travels through the earth's
crevices, before exiting on the surface at some
distance and at a lower elevation than its
origin.
Fortunately, obvious symptoms exist to help
track down the source of the water in a wet
basement. Wall stains, peeling paint,
efflorescence (soft white crystals), or moisture
on walls are all signs of surface water. So are
seepage around windows, silt within the water
and seepage that begins and ends approximately
with the start and stop of the rain. This kind
of seepage may often be localized in the corners
or along one wall.
If the source of the problem is ground water,
the water is almost always clear. Usually it can
be found coming in around all wall floor
intersections and where plumbing pipes go
through the basement floor. When ground water is
the culprit, the homeowner is not likely to
notice it until long after the rain usually
days.
The key to curing a majority of basement seepage
problems lies in preventing soil saturation in
the soil close to the house and the resulting
pressure it creates against the foundation of
the house. The grade immediately next to the
foundation should always slope away from the
house to shed surface water.
A proper diagnosis of a wet basement should
start by determining where the water came from.
There are three primary sources:
If the source of the problem is spring water, it
can be visible either continuously or
seasonally. A continuous spring will cause year
round seepage, while a seasonal spring, which is
usually more forceful, can be very destructive.
Seasonal springs tend to cause flooding
continuously for days and even weeks after the
rains have stopped. Occasionally the water
intrusion can burst a floor slab upward.
In poorly drained soils almost all wet basements
are caused by surface water. In such areas it is
sometimes estimated that only one house in 300
is built in an area where there is rising ground
water. If your house is significantly lower than
others in the area, then you might be that
one-third of a percent case.
Before you do anything about a wet basement, it
is important to get a good, unbiased diagnosis.
Waterproofing contractors cannot always be
considered unbiased and may recommend expensive
and unnecessary work. A home inspector or soil
scientist can often provide a professional
diagnosis, as well as written specifications to
solve the problem.
Since almost all wet basements are caused by
surface water, the cure involves implementing
surface-water controls. Because pressure builds
up when the soil is saturated, all efforts
should be directed at relieving soil saturation
near the foundation. (No pressure means no
seepage.)
These efforts involve making certain that the
gutters and downspouts deliver their waters well
away from foundations. Downspouts should be
extended with corrugated solid plastic piping to
empty at a continuous down-slope or into a
drywell.
Voids (or empty spaces) under slabs should
always be filled. Probe for them under porches
and stoops, patios, sidewalks and even under
basement entrance steps. All voids should be
tightly packed with clay soil. The grade or
slope of soil against the foundation should be
angled down and away from the wall. (If need be,
basement windows can be protected with
corrugated window well material.) The grading
soil should have a heavy clay content, be
tightly packed, and drop off at a one inch fall
rate per foot as the pipe runs out and away from
the building. The grade should extend six feet
from the house.
Yards that slope toward the house should be
intercepted on the surface by "swales" (or
earthen troughs) to catch runoff water, which
should then lead the water around or away from
the house. These measures are often inexpensive
and relatively easy for the homeowner to do;
however, landscape contractors will often do
such work on an hourly basis.
A professional water proofer is likely to
suggest one of several methods to cure wet
basements. Most of them involve containing the
water or channeling it to pumps inside the
house, of digging up the outside yard and "parging"
(a trowel-applied coating of Portland cement)
over the foundation walls. Another method is the
"French drain" interior system, which utilizes a
trough with a perforated drain pipe that is
installed under the floor and around the
perimeter of the basement. The trough leads to a
deeper hole containing a sump pump. This
approach, which can be both disruptive and
costly, involves smashing through the slab to do
the installation.
The "cove" system involves cementing a plastic
or metal plate to the floor and wall to dam up
any incoming water. It is then channeled to the
hole containing the sump pump. This system,
which often involves drilling through the
foundation wall first to promote rapid drainage,
is cheaper and easier to install and is less
destructive. Remember, the inside pickup systems
do not address the source of the problem only
the unpleasant symptoms.
For further information, consider the booklet:
"Wet Basement Diagnostics"
Training, Learning, Certification, Inc.
2841 Hartland Rd., SU 201
Falls Church, VA 22043
$15 plus $5 shipping and handling