MIKE HOLMES: How to keep your basement dry
Keeping water out of
basement starts on the ground
The simplest thing you can do to keep water out of your
basement is to control it at the surface. Surface water, like rain or
melting snow, or water from irrigation, is pretty easy to control, compared to
water below grade. There's not much you can do about underground
streams, or water table in your area and the resulting hydrostatic pressure on
your foundation. But there's a lot you can do on the surface. Most of the problems homeowners have with wet
basements can be prevented if people correct the grade around their home.
Make sure that surface water doesn't become groundwater and add to the pressure
that's already down there.
The first step is to make sure that surface water drains
away from your house. Ideally, you want the soil level right next to
your foundation to slope away. Since water flows downhill, surface water,
like rain and snowmelt, will flow away from your basement walls. If the
soil around your home has either a flat or a negative grade, surface water will
naturally flow towards your home or pool around the foundation. This
will lead to trouble.
I'm going to
hope your home is built right, and that the top of the foundation is at least six
inches above the soil. That's minimum. But the higher the
better. Also, the soil level needs to fall away -- on all sides -- in a
slope away from your house. Bad grading can result in water pooling next
to the foundation, which can lead to wet basements. You might live in an area where the general
drainage comes towards your house -- maybe you live at the bottom of a hill,
below other houses. In this case, the grade needs to be altered to direct
surface water away. Usually a swale is used to intercept and collect the
water that's running downhill towards your house and take it around and release
it lower down the slope. (If that sounds like your situation, you will
definitely need to have a professional assess your lot's drainage).
When a house
is built, there's always an excavation for the basement and foundation.
That is eventually backfilled, of course, but the soil right around the
basement's exterior walls is never as firmly compacted as undisturbed
soil. It's more porous and will always contain more air -- which will
allow water from rain or melted snow or irrigation from plantings -- to collect
and seep down to your foundation level. That's
one reason I don't like plants around a house's foundation. It's not
beacuse I don't like plants, but the irrigation into disturbed soil brings and
retains too much moisture near basement walls.
When that backfill soil does eventually settle, after many
years, there's a depression right around your home that will fill up like a
bathrub with surface water. And most homeowners by then will have
landscaped the area and won't even notice that the soil several feet out from
their house is lower than further out into the yard. If you don't re-grade that soil, the water
will continue to pool and gather in the lower spots and eventually make its way
down to your footings.
An easy fix is
to make sure the downspout from your eavestroughs comes down, and expels water
as far away from house as possible -- at least two metres (six or eight
feet). If you don't make sure the downspouts expel water far enough away
from your foundation -- beyond the area of backfilled, uncompacted soil -- you
are pouring water down to your footings.
In older houses, the downspouts were often connected to the main stack
and the sanitary line. Now they are tied into a storm line in the
street. In older homes it's a good idea to disconnect the downspouts and
have them empty above the surface.
After a number
of years, it's likely the weeping tile has shifted or broken or is full of tree
roots, and every time rain comes down those downspouts it has nowhere to go but
up against your foundation, putting lateral hydrostatic pressure against those
walls, which could one day crack the foundation. Or it could cause a
sewage backup into your home, which you definitely do not want.
You may find you need to direct water away beyond the end of the
downspout, or from a low-lying area next to your house. The best fix is
to put in a French drain, which is basically a shall trench filled with gravel
that will carry excess groundwater away from your house.
A French drain
relies on gravity and on the grade to divert surface water. It needs to
be as deep as the lowest point of the pooling water at its start, and it slopes
downs to where you need it to empty. Simple. Line the trench
with landscape fabric, fill it with gravel and put more fabric on the
top. Then you can sod over it to camouflage it as part of your
lawn. You can also use a length of plastic weeding tile with a sock buried
in the gravel if you like. Before you
dig a French drain, make sure you aren't letting the water out onot a
neighbour's property. And make sure your downspouts don't empty on or
over the property line. Ideally they'll empty onto your lot, or into a
drainage swale between two adjoining lots.
supposed to happen, but over time homeowners do landscaping projects and
renovations, and little by little they can significantly alter natural surface
drainage patterns until they create big problems for people next door. Be
aware of how your plans might affect surface water drainage.
News article supplied by Winnipeg
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