Cottage Q&A: Wet crawl space solution

A concrete crawl space, surrounded by soil By Rick's Photography/Shutterstock

We have a wet crawl space. It’s poured concrete, and at the level of the water table. How can we keep water from getting in?—Helene Yaremko-Jarvis, Lac Sergent, Que.

Ordinarily, when water is getting into basements or crawl spaces, “it’s directly related to landscaping or downspouts,” says Roger Frost of Napoleon Home Inspections in Barrie, Ont. If your downspouts aren’t sending water far enough away from the cottage, you can extend them; if the land around the cottage doesn’t slope away from the building, you can landscape to steepen the grade.

But if your water table is consistently high, say, because your cottage is in a swampy area, such go-to fixes won’t work. “You’re fighting against nature,” says Don Fugler, a building scientist formerly with the Canada Mortgage and Housing Corporation. “The cottage is a boat floating in a pool of water.”

Is your cottage at high risk of flooding? Consider “wetproofing.”

Assuming you have electricity, installing an interior sump pump is an option—though it’s a “quick and dirty” solution, says Frost. More effective: trap the water before it can reach the crawl space. Fugler suggests that you dig a trench around the perimeter of the cottage, slightly deeper than the base of the foundation, and backfill it with gravel. This moat could then drain towards the lake. (If the ground is flat, you’ll still need power: an exterior sump and pump.)

Unfortunately, “if the cottage was built so the crawl space floor is actually below the level of the adjacent lake, none of these solutions is going to work well,” says Fugler. You’re left with mitigating the effects of regular dampness. Use an exhaust fan or a dehumidifier in the crawl space, and watch for signs of rot in the floor joists and headers. It’s probably not the fate you’d want for a heritage building, says Fugler, “but it is a cheap fix for a simple cottage.”

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This article was originally published in the Summer 2018 issue of Cottage Life.


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