Prevent Water From Entering Your Crawlspace

Underground, pressurized water can turn any basement or crawlspace into a “relief” valve, particularly when the underground water is moving below the level of the foundation beams. Even lining the crawlspace with thick plastic and installing a gravel layer for weight cannot always prevent this pressurized below-ground water from making its way into your crawlspace.

One very effective solution to this problem, albeit an expensive one, is to install a concrete slab, with a thick underlayment of waterproofing plastic below. This will prevent pressurized below-ground water from making its way into the structure.

However, not everyone can afford to spend nor wants to spend the money for a concrete slab in their crawlspace. In these situations, many home builders will install a submersible sump pump for pumping out water that inevitably finds its way in.

This solution is workable, but it’s messy and requires routine maintenance. It also resigns you to an occasionally wet, dank crawlspace. Ick!

There is another way! Water always finds the easiest pathway to relief. Therefore, if you cut a drainage trench outside the foundation that is below the crawlspace, you can prevent water from reaching your crawlspace in the first place.

Many times, you can use the trench you dig for sewer and water yard lines for this purpose, or if your sewer tap depth disallows this, you may need to dig an additional trench. In either case, dig your trench up to the side of your foundation that fronts the collecting water. Locate the bottom of your trench at least 8” to 12” below the crawl space grade and water will preferentially fill your trench and leave your crawlspace alone!

I recommend installing a French drain, surrounded in filter fabric and gravel, so that you can take that water to daylight or a collection reservoir. Typically, you can use dirt for the final 6” to 8” of fill so that your landscaping will hide your trench. No more sump pump!


  • Drew

    A sump pump is definitely the best way to get water out of your crawl space. Great advice to use a French drain. That will for sure make a huge difference. Thanks for posting.

  • Ethel Stowne

    I didn’t know that a crawlspace could be a release area for water! Installing a concrete slab is a great idea for preventing water from getting into your crawlspace! These tips will help keep my home mold and moisture free, thanks!

  • Kit Yturralde

    We have created an article on how to prepare your crawl space for encapsulation and a dehumidifier. It is definitely worth looking at I think:

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