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Question DetailsAsked on 6/10/2011

Water in the crawlspace - what would you do?

The previous owner put down a vapor barrier on top of gravel in our 5 foot tall crawlspace. So far, so good. Twice in the last 2 years, however, the crawlspace has flooded. Now there's water on top of the vapor barrier. My intuition is telling to remove the plastic vapor barrier, since it does no good when there's water on *top* of the vapor barrier. If I replaced it, the next time it floods, it would become useless, because the plastic shifts around and leaves half the crawlspace uncovered.

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7 Answers



The water issue is probably due to a grading issue outside your foundation. Some of the more common caused in getting water in a crawlspace are:

1. Yard slopes towards the foundation and usually ponds adjacent to foundation in low areas.

2. No gutters and/or gutters dump water next to foundation.

Answered 8 years ago by rmayo


Oooh. I just noticed I didn't post the reason water gets in the crawlspace. My bad.

We have water seep in from below (gravel floor) during periods of heavy (3-4"+ in 24 hours) rain. In fact, we live in a flood plain, so when it rained 8.5" in 24 hours, water overtopped the foundation and got into the crawlspace that way.

However, the foundation and crawlspace walls were sealed 5 years ago. For whatever that's worth, when you consider water was entering the crawlspace over the top of the foundation!

Answered 8 years ago by LpAngelRob


If water is likely to enter the crawspace again, you would be better suited to seal the vapor barrier to the underside of the floor and provide proper ventilation for that are to allow it to dry out.

Insulated the underside of the floor, air seal it, and apply a vapor retarder.

Answered 8 years ago by Windows on Washington


Hi Rob,

We went to highly rated service companies on Angie's List to get their take on your problem and potential solutions.

First, you’re right. Water on top of the vapor barrier (which helps keep ground moisture from entering the home) is a problem. Neither replacing it each time the crawlspace floods – nor leaving it alone – will solve your problem, though. You need to find the source of the water penetration. Correcting the flooding issue will resolve everything else, and it might prevent some issues you don’t have yet, but are certain to come if you don’t plug your leak.

Standing water in your crawlspace can lead to serious health issues as a result of mold growth, plus it could cause significant damage to the structure of your home. The source of the water could be from the ground sloping toward your home, rather than away; downspouts discharging water too close to the foundation; the absence of a sump pump and perimeter footing drain system, or a malfunction of those; cracks in the foundation; or plumbing leaks.

A qualified home inspector or structural engineer can help determine your problem and offer recommendations on how to correct it. Once you have eliminated the source of the water, you should ensure the area is dry, have any mold growth remediated or other damage repaired, and then replace the vapor barrier. Adding gravel on top of a new barrier can help hold it in place. Be sure to get estimates from at least three different contractors for any repairs and always check references.

I hope that helps some. Good luck~!

Paul from Angie's List

Answered 8 years ago by Paul from Angie's List


We had a high moisture problem in our crawlspace. We had gutters, proper sloping, perimeter drain, sump pump. We installed a thermostat controlled ventilation system and that did nothing to control the high humidity levels in the summer here in central Indiana. We only had the sump pump working in heavy rains every few years. We hired the Crawlspace Doctor and they sealed the crawlspace vents, moved the sump pump to the lowest level, insulated the block walls, installed a heating and cooling vent from our heat pump system to the crawlspace to create positive airflow, and put down vapor barrier on the floor. It works very well. It has been in for a few years. There was a study done in the southern states by Habitat. You can find it online by doing a search on sealed crawlspaces. We are paranoid so we also went for a backup sump pump just in case. Our sump hasn't had to work for years since the groundwater is not a problem now.

Answered 8 years ago by Pooka49


I was looking at your question as a possible reference for another person with similar issues. Don't know if you solved your issue entirely or not, but I had one thought - if you have occasional high water and cannot solve it by redirecting outside flow and roof runoff, but you can live with a few days of dampness every few years, your vapor barrier issue could probably be solved by pulling it back and regrading your gravel bed, to provide a slope on the vapor barrier when replaced so it will drain to your sump. Could probably do this creatively, after padding or rounding board ends so you don't puncture the VB, by nailing treated timbers together (copper ground-contact rated wood, the green type) long enough to reach all the way back in, and using them to create troughs in the VB so it drains when water gets on top of it. IF water gets deep enough to float wood, you would have to fasten them down, or maybe use pavers or such instead - or levate the edges of the VB at the foundation walls to provide a natural slope to the middle and downhill from back to front, if you use maybe 10 mil visqueen rather than the thinner norml 3-6 mil construction grade.

As for the VB shifting around, the VB has to be fastened to the foundation to really work right - usually caulk at the interface with the wall, then boards fastened through the caulk seam into the concrete with concrete nails or insert-type drywall fasteners. Could be done when you regrade or add to the gravel to slope right.

Answered 6 years ago by LCD


1. What mil vapor barrier do you have? Anything less than a 10-mil vapor barrier rips extremely easily.

Do you have a crawl space dehumidifier? Are your crawl space walls sealed? By chance, do you have any soft or bouncy spots on your first floor? Water in your crawl space can be from water vapors, an ineffective vapor barrier, drainage and grading problems, a crack in your home's foundation, a broken sump pump, and a multitude of other factors. A fully encapsulated crawl space, which includes sealing off vents, walls, a specialized dehumidifier, and sump pump system will tackle the crawl space moisture problems you're experiencing. You may also want to consider SmartVent flood vents (which are FEMA approved); if you live in a flood zone, give you a way to prevent extensive property while also reducing flood insurance rates.


Answered 4 years ago by JESDani

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