By: Doug Herbert
Few things in a home are more frustrating than a leaky
basement. Nail pops in the drywall…no
problem. HVAC unit stop working? It’ll cost you, but you can get a new
unit. Roof leaks? It may take a few thunderstorms to isolate
the leak, but you can get it stopped.
However, water coming into the basement can be a
completely different animal. Finding and
fixing the problem can sometimes mean digging up the flowerbeds and bushes, or
tearing out a decorative patio
to get down to the problem. That can be very expensive and
time-consuming. Nobody wins in these
difficult situations.
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Our foundation has been waterproofed and is ready for backfill.
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Those complicated scenarios, though, do not represent 90%
of the water problems that are associated with basement foundations. Waterproofing products used today are very
effective at stopping water from entering the basement. Often, water issues have little to do with
the actual waterproofing that was applied to the concrete wall. The majority of
waterproofing problems occur above the waterproofing that was applied to the
wall.
For waterproofing to be effective, it needs to work as a
complete system. That system is
comprised of three areas:
1. Water drainage at footing and slab elevation (French
drain). A drain tile, strip drain
or integrated footing form with drain is needed next to the footing. This collects the surrounding water and
directs it to an interior sump pit or to open drainage at a daylighted area.
2. Membrane applied to concrete wall. The most common product is spray-applied
elastomeric waterproofing. An additional
drainage board or material can be installed over the waterproofing to improve
drainage down to the drain tile and protect the waterproofing material during
backfilling of the basement.
3. Water management at finish grade and above. This is where most problems occur, and the
area that we will focus on.
The four areas that follow should serve as your primary
troubleshooting guide to basement water issues, and will likely cover 90% of
the water issues you have with your basement foundation. If you have water coming into your basement
foundation, evaluate your situation against each of the following items.
Slope
Finished Grade
The Concrete Foundations Association of North America
publishes the CFA Standard for foundation construction. They specify that the grade has to slope away
from the foundation; specifically it has to have a slope of 6” within the first
10’-0” out from the foundation. Without
proper slope, rain water can pool on the surface. It will then work its way down through the
backfill and accumulate next to the concrete wall and footing. If it isn’t efficiently removed by the drain
tile, it will find its way into the basement.
To prevent this, ensure that the grade slopes away from the basement
foundation on all sides of the home.
Finished
Grade Below Waterproofing
It is important to keep the finished grade below the
waterproofing that is applied to the wall.
If the grading contractor backfills the soil above the line of
waterproofing, then water can enter the basement through a shrinkage crack that
isn’t covered by the waterproofing.
Water entering through the outside will often reveal itself on the
inside a few feet below the entry point.
You may think that it is coming through the outside of the wall at the
same point you see it inside the basement, but this is often untrue due to
gravity. The finish grading isn’t the
only area to watch out for. At times,
another couple of inches of topsoil are added over the grading. Also, during landscaping, mulch will often be
added. This all adds up to a foot or
more of soil above the line of waterproofing, which increases the risk of water
problems in the untreated area of the concrete wall. Be sure that you can see a small amount of
waterproofing on the basement wall after the final landscaping is finished.
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Waterproofing is sprayed onto the face of the concrete wall.
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Address
Backfill Settlement
When the basement foundation is backfilled without
compaction of the soil, the soil adjacent to the basement wall will settle over
time. This will leave a depression in
the soil, causing water to collect next to the wall. When water is allowed to accumulate next to
the wall, it will find a way into the basement.
Evaluate the soil for settlement during the construction of the home. Before the landscaping is finished, be sure
to fill in any depressions in the soil.
Homeowners should watch for further settling of the soil and to fill in
the depression before it creates a problem.
Weep
Holes In Brick
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Drainage board has been installed on this Texas
foundation that we
constructed.
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Most people assume that a brick or stone façade is
water-tight. The fact is that in a heavy
thunderstorm rainwater penetrates through the façade and gets into the airspace
between the brick and framing. The water
travels down to the basement wall’s brick ledge and is intended to escape
through weep holes in the brick.
Oftentimes those weep holes have not been installed. Or, they have been installed too low and the
backfilled soil covers them up. This
will cause water to build up within the airspace between brick and framing. Proper flashing in this area is
critical. The water doesn’t always
reveal itself at the same location that it is coming in. It may travel along the top of the concrete
wall until it finds a shrinkage crack and then come into the basement a few
feet down from the top of the wall. If
your house has brick on it, be sure that weeps have been installed and they are
above the finished grade. This will
prevent many water problems.
These four items are some of most common problem areas
that allow water to come into the basement.
Basement waterproofing needs to be viewed as a whole-house system that
includes weep holes in the brick, proper flashing, downspout orientation and
other issues that are above the line of waterproofing. When you address each of these areas, you
will be well on your way towards preventing a lot of headaches, frustration,
and angry homeowners.
The
unabridged version of this article was originally published in the July 2013
edition of Concrete Homes + Low Rise
Construction Magazine.