What Is a Crawl Space Vapor Barrier? 

A crawl space vapor barrier is a durable, waterproof liner that seals off crawl space areas from outside elements. It covers the ground floor, walls, and support beams and prevents moisture intrusion.

With other encapsulation measures, such as drainage systems, sump pumps, dehumidifiers, drainage matting, and insulation, vapor barriers are an effective crawl space moisture barrier. 

How Do Vapor Barriers Work?

Think of vapor barriers as a protective shield for your crawl space. These thick plastic sheets are laid across the ground, creating a continuous layer that stops moisture migration. But keep in mind—they only block ground moisture. If there’s runoff or a plumbing leak, you’ll need additional waterproofing measures to keep the space dry.

Do You Really Need a Vapor Barrier?

If you’re building in a dry climate, you might think a vapor barrier isn’t necessary. But don’t be so sure. Even in areas like Arizona, the ground holds surprising amounts of moisture. In fact, a study by Advanced Energy found a 15% annual energy savings in buildings with sealed crawl spaces, proving that controlling moisture also improves efficiency.

If there’s a crawl space, a vapor barrier is worth considering—no matter where you’re building.

How Thick Should the Barrier Be?

The Crawldryer vapor barrier comes in 10 and 15-mil thickness options. The choice depends on the level of protection required. Since crawl spaces don’t have the added protection of a concrete slab, durability is key. The standard for plastic vapor retarders is ASTM E1745, and PERMINATOR exceeds those requirements, ensuring you get the best protection possible.