| Wet
Basements
By
Gil Strachan
Technological advances in recent
years now allow most modern basements to be made into comfortable
living space. However, all basements
are vulnerable to some water penetration during their lifespan.
Drainage tile, damp-proofing and moisture barriers all assist in
preventing moisture from entering the structure through the foundation walls. Even with
all these in place, if the area experiences an unusually high level of precipitation and
the ground becomes saturated with water, the tile system may not be able to handle the
volume and the hydrostatic pressure that builds up along the foundation wall may force
some of the water through hairline cracks and/or pores in the foundation walls. Older
homes that may not have the advantages of modern technology and those that have more
porous types of foundations (block, brick, stone) may be even more vulnerable.
Much of this can be prevented by ensuring proper evestroughing and
downspouting systems and by ensuring the slope or grade of the lot is directed downwards
away from the structure. In most cases you will be able to spot previous moisture or water
penetration, however it is possible that a basement which has not leaked in the past may
in the future if the conditions for leakage occur...
Another potential source for water in a basement is from a drain
backing up. This type of situation is generally unpredictable unless there is evidence of
a previous occurance. Indications of potential problems are homes in older areas of a town
or city, where the municipal system is smaller and where the home owners' drains may be
somewhat restricted by soil, tree roots, or accumulation of debris. Large deciduous type
trees located in the path of a drain system should be considered as a potential problem.
Although a backed-up drain may appear to be a serious problem, the
inconvenience of water coming into the basement can typically be prevented by the simple
installation of a device called a backflow preventer or check valve. This device allows
water to flow down the drain, but will not allow it to back up. Drains that have
completely collapsed or are seriously blocked or deteriorated may need to be excavated and
replaced.
If you do have water in your basement, I suggest that you research the
circumstances thoroughly and have an unbiased professional diagnose the situation before
taking any remedial action or beginning any work.
DID YOU KNOW?
Did you know that basement leaks are the
number-one major complaint from new home
owners? According to Ontario New Home Warranty Program (Tarion)
statistics, the average basement develops two leaks in the first two years after
completion. The notable areas are cracks, form tie holes, and honeycombing.
In this day and age, we regard a dry basement as a
reasonable expectation, but unfortunately, practice doesn't always follow design. Building
a dry basement requires an effective drainage system and wall assemblies that are more or
less water resistant. Now, what's under and around your house, barring any great
re-constructive projects, is likely there to stay. So, the only realistic and
cost-effective means of control that we have as homeowners (especially in older homes,
without drainage systems) is to control run-off from on and around the house.
 What's surprising, is that something as innocuous-looking as a
low-lying flower bed can often be the major contributor to a wet-basement problem. Take a
long, hard look around the house. Are the eves all fitted with evestroughing, and do the
troughs drain freely into downspouts and discharge at least two meters away from the
house? Has the backfill around the foundation settled? Any other low-lying areas? Watch
where the water goes during a rain storm, or spring melt. If water drains from the street
or other areas, towards your house, consider landscaping features which can guide the
water away.
Different types of water ingress:
PERSISTENT: Occuring frequently throughout the
year. Persistant leakage will almost always leave noticeable signs and clues,
whether the basement is finished or not.
What to look for: Staining on the first 6-12 inches up from the
slab, bubbling or peeling paint, effluorescence (white salts), damp musty smells.
SEASONAL: Generally occuring only at time of
peak rainfall or other surface run-off, usually in the spring or fall. Seasonal
leakage is more difficult to identify unless the leak is actively occuring.
What to look for: Stains on finished surfaces or stored items, rust
on the bottom of appliances, raised storage.
ONE-TIME ONLY: Occuring only when very specific
conditions exist. This type of leak may occur once in the life of the basement, or
may occur every few years when the appropriate conditions exist. One-time leaks
(somewhat of a misnomer as they can, and frequently do, occur more than once) are the
hardest to identify, again unless an active leak is occuring at the time of observation.
Gil Strachan represents Electrospec Home Inspection Services, specializing in pre-purchase
inspection of resale residential properties. For free information, or a copy of this or
any other article in the series, please call toll free 1-888-394-6954 or send
email.
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