Waterproofing Woes? Here’s What to Do About Water on Top of Your Vapor Barrier

Mariel Loveland
Written by Mariel Loveland
Updated January 11, 2022
A basement in luxury home
Photo: pics721 / Adobe Stock


  • Vapor barriers are plastic or foil sheets used to damp-proof a space.

  • Poor placement, improper installation, or incorrect permeability can cause water on a vapor barrier.

  • Use a wet/dry vacuum or water pump to remove standing water.

  • Use a dehumidifier to remove excess moisture.

  • A professional waterproofing contractor can diagnose and fix the cause of water.

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So, you thought the vapor barrier in your wall, attic, crawl space, or basement would keep your home dry—and it didn’t. Now what? Don’t panic. Vapor barriers on their own often aren’t enough to stave off all moisture. If there’s a little (or a lot) of water on top of your home’s vapor barrier, there’s a reason. Here’s what you can do.

What Is a Vapor Barrier?

A vapor barrier, or vapor retarder, is any material used to damp-proof a space. It’s no secret that water can rot building materials or foster mold growth in your home. Vapor barriers stave off water damage by preventing water vapor from seeping into areas of your home (in a process known as vapor diffusion) where it can condense and cause damage. 

Most builders install vapor barriers in areas of high humidity like:

  • Crawl spaces

  • Basements

  • Bathrooms

  • Greenhouses

  • Spa rooms

Usually, vapor barriers are made from some kind of plastic (like polyethylene vapor barriers) or foil (like non-perforated radiant heat barriers, which are popular in attic insulation). They have a perms rating, which rates their permeability. Believe it or not, fully impermeable isn’t always the best choice.

What Causes Water on Top of Your Vapor Barrier?

A frame construction of wooden house
Photo: Sukhorukova / Adobe Stock

If there’s water on your vapor barrier, removing the water and fixing the water damage is just a short-term solution. To fix the issue for good, try understanding why there’s water in your crawl space, basement, attic, or wall. 

A pipe leak is self-explanatory, but condensation could be the result of:

  • A poorly sealed space

  • Improper ventilation

  • Improper vapor barrier installation 

  • Improper vapor barrier placement

  • An impermeable vapor barrier where you should’ve used a semi-permeable barrier

For example, vapor barriers usually work best when they’re installed on the side of the wall that experiences the most moisture and highest temperature. So, in a hot climate, you’d want the barrier on the exterior of a wall. Permeability is also an issue. A fully impermeable barrier may work for crawl space encapsulation, but it can prevent condensation from drying out in an air-conditioned space. 

Since waterproofing is complicated, it’s best to hire a top-rated waterproofing contractor to find the source of excess moisture.

How Do You Get Rid of Water on Top of Your Vapor Barrier? 

If you have water on top of your vapor barrier, don’t worry. There are multiple ways to handle this so you keep your crawl space, basement, or attic nice and dry. 

Here are a few solutions for getting rid of water on your vapor barrier. 

Use a Wet/Dry Vacuum to Suck Up Excess Water

Whether a pipe burst, your siding cracked, or a particularly rough storm flooded your basement, you’ll need to remove any standing water on top of the vapor barrier before you can do anything else. 

Use a wet/dry vacuum to remove as much water as possible. Depending on the area, be careful not to accidentally suck up any loose insulation or soil.

Use a Submersible Pump

Sometimes, there’s too much standing water on your vapor barrier for a wet/dry vacuum. If your wet crawl space or basement has completely flooded, you’ll need to pump out the water. You can purchase a water pump at your local home improvement store.

Crawl space water removal is sometimes complicated. After severe flooding, you may need to remove and replace the vapor barrier so the whole space can properly dry. A waterproofing contractor can make sure it’s done right.

Dehumidify Your Space

A wet crawl space or basement can lead to a big mold problem. If you see water on the vapor barrier, there’s a good chance it’s also soaked into porous areas of your home (like your wall’s insulation or concrete foundation). You’ll need to dehumidify the space. 

Enter: the trusty dehumidifier. This can be a temporary or permanent solution, depending on the reason for excess moisture.

Make sure to choose a basement or crawl space dehumidifier that works with your space’s square footage. If your home is particularly humid, you may want to splurge on a model that hooks into your HVAC system and dehumidifies your whole house.

When Should You Hire a Pro to Make Crawl Space Repairs?

A vapor barrier may work well in a bathroom or home spa, but isn’t typically enough for basement or crawl space waterproofing alone. In cases of repeated basement or crawl space water issues, make sure your crawl space is up to code

Hire a professional to inspect your space and make crawl space repairs. This could include:

  • Fixing cracks and holes with sealant

  • Repairing your vapor membrane

  • Installing water-resistant insulation

  • Adding crawl space vents and fans to stave off moisture 

  • Installing a waterproofing system, like a sump pump and french drain 

FAQ About Water on Top of Vapor Barriers

How can I get rid of moisture between the vapor barrier and the insulation in a basement?

A dehumidifier can help remove moisture, but you’ll need to diagnose the source of the problem to get rid of the moisture for good. In this case, it’s best to hire a professional. 

What if my insulation is wet?

If your insulation has water damage, you’ll probably need to replace it. The cost to insulate a basement is typically between $1.50 to $2.50 per square foot. Consider installing water-resistant crawl space insulation, like closed-cell foam insulation, with the help of a local insulation contractor. Spray foam can insulate around pipes, but a waterproof rigid foam board works well in walls. 

What’s the best way to seal a crawl space and insulate?

Soil is a magnet for moisture, and it can seep into crawl space walls and concrete foundations. If you have exposed ground, you should probably encapsulate your entire crawl space. 

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