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Crawl space water after heavy thunderstorms/rain

matt6962 | Posted in General Questions on

Hi, I have been working on insulating and sealing my crawl space in Zone 4 central VA in a 1950s brick rancher. I noticed signs of water entry days after heavy rain with small puddles on the existing vapor barrier. The existing vapor barrier is standard black 6 mil poly which has been laid on top of old tar paper/shingle like vapor barrier. The seams of the vapor barrier are not taped or sealed.

I’m certain this water is not from condensation or plumbing leaks. My guess is that due to the crawl space being a step down one where it is 8-10 inches below grade and the area having a high water table that during and after heavy rain the water table rises higher than the level of the crawl in certain areas. The only other reason I can think of for the water entry is a hole/holes in the foundation below the grade in the crawl space where water enters and pools in the crawl space. I went under there recently after a thunderstorm and saw a pretty large puddle about 15 feet by 2 feet on top of the vapor barrier right by the front left wall. When I crawled closer to it I noticed that the liner nearby was floating on a bit of water. The crawl space is generally level, no big slopes or trenches really and the outside grade slopes away from the house with gutter extensions to carry the water away from the foundation. I’m wondering what the best course of action is to address this water issue? Does drain tile need to be put in on the front wall which goes to a sump? I have had a few companies come and look at insulating and sealing the crawl space and told them I noticed small puddles in the crawl space days after rain. Only one of the companies recommended drain tile on the front wall but none of them have seen it right after heavy rain. I appreciate any advice you can offer.

Thank you.

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  1. Jon_R | | #1

    There are various classical solutions (eg, gravel to drain crawlspace water to a sump). But for something different and speculative, consider Styrofoam packing "peanuts" under the plastic sheet. They should float up whenever there is water under the plastic, keeping the plastic above water and avoiding water ponding above it. Or use the similar floating pool cover plastic sheets.

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