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What Is A Vapor Barrier?

A vapor barrier is a thin layer of impermeable polyethylene sheeting that prevents moisture from seeping through your basement or crawl space walls (and floors). This barrier is around 10 to 20 millimeters thick and catches water and moisture seeping through your concrete, channeling it downwards to a connected drain tile system. If you have drywall or paneling on your basement walls, this will protect them from being ruined by mold, moisture, or rot. Note: In order to apply a vapor barrier to a finished basement, we will need to remove any finishes.

A vapor barrier will lower the temperature in your basement or crawl space, reduce humidity, and prevent moisture from damaging stored items, including structural supports such as joists.

When To Use A Vapor Barrier With Insulation

Insulation will prevent air from entering or escaping your basement, but it will not stop moisture diffusion. A vapor barrier will stop moisture diffusion and should be applied directly to your concrete walls (plus crawl space floors). If you decide to add insulation in your basement, it should be applied after you install a vapor barrier.

How Do We Install Vapor Barriers?

The vapor barrier installation process is straightforward. First, we make sure your crawl space is clear of any debris. If you have a basement, we’ll need to remove any finishes on your walls, such as drywall or paneling. The next step involves wrapping the sheet along your walls (and crawl space floors) and sealing the edges using waterproof seam tape.

Our Basement And Crawl Space Waterproofing Services

Contact The Real Seal For Basement and Crawl Space Vapor Barrier Services In Chicagoland

If you live in Chicagoland, call The Real Seal today. We’ll inspect your foundation and find out why water is seeping into your basement or crawl space. Vapor barriers are just one part of our complete foundation waterproofing system, which also includes a drain tile system and sump pump. Schedule your free foundation inspection today and receive your personalized estimate.

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Vapor Barrier FAQs


What material can be used as a vapor barrier?

The Real Seal uses 10 to 20-mil thick impermeable polyethylene sheeting.

Can I install a vapor barrier myself?

Yes, you can install a vapor barrier yourself. But if you want the job done correctly without stressing and crawling in a confined space, call The Real Seal.

How long does a vapor barrier last?

Our vapor barriers will last for life and can even outlast the foundation.

What is the difference between a vapor barrier and a moisture barrier?

The terms vapor barriers and moisture barriers are used interchangeably.

What happens if you don't install a vapor barrier?

Without a vapor barrier, your foundation is at risk of increased humidity, condensation, water damage, and more.

Does mold grow under a crawl space vapor barrier?

Mold does have the ability to grow under a vapor barrier if there is organic matter. A professional company should clear that material before installation so there is nothing for mold to grow on. Additionally, Real Seal’s vapor barrier has an anti-microbial additive to help prevent the growth of mold.

Will a vapor barrier reduce humidity?


When should I replace my vapor barrier?

If you notice your vapor barrier is ripping or falling apart, call The Real Seal for an inspection. Our vapor barriers come with a lifetime warranty.