I asked a few crawlspace waterproofing company came to look at my wet
crawlspace and they all suggested a system similar to a french drain around
the inside perimeter of the foundation wall. It would terminate in a sump
basin (bucket) that contains a sump pump with the output connected to a
Since the foundation is resting on soil, wouldn't digging a trench in the
soil near the footing weaken the soil's lateral support and lead to
settlement (sinking)? They would fill the trench with wash rocks but still
it would not be as densely packed as undisturbed soil.
That's standard. The trench that they dig is only 4-6" deep, and it
won't affect the foundation. Basically, they are building a little
gutter just inside of your foundation walls. I had this done on a
house I renovated once, and it worked great in conjunction with some
1)Be sure your gutters are clean and that water isn't rolling off of
your roof and sinking into the ground near the foundation walls.
2)Be sure you have a proper drainage slope for the grade near the
exterior of the foundation walls.
3)Use retaining walls if necessary to keep water from rolling downhill
towards your foundation.
4)Use a dehumidifier in the crawl/basement, and feed the accumulated
water into the trench that the foundation company is digging.
You can get more info at my website.
Hope this helps,
Builder/Instructor at Emory University
Author of www.renovation101.com
Do you need a drain system, is it just humid or is it flooding, did you
do everything else, grading, have down spouts not drain nearby, you
might need 10 ft extensions. Or is it just humid , something vents and
plastic on the ground might cure.
It pays to cover all other bases before resorting to doing a french drain.
We moved into a house in August that had real problems with water in the
basement. The previous owner(s) had taken some real half-arsed measures to
correct, which probably cost them $10,000 all told.
I graded around the foundation which took care of 95% of the problem. I put
a drain box in a low spot in the backyard and piped it to the street which
took care of the rest. Gutter covers kept the gutter free of leaves. Total
outlay $500. It took a little tweaking with the grading but the basement has
stayed bone dry through 3 multiday rains.
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