If you have moisture in the crawl space, you’ve likely been doing your research and learned you’ll need crawl space vapor barriers. We call this crawl space encapsulation, referring to the sealing up the crawl space to eliminate the moisture problem.

If you’re choosing to encapsulate your crawl space, one of the important decisions you’ll have is choosing between a wide range of different crawl space vapor barrier types. There’s several different vapor barrier sizes you’ll need to consider. Also known as crawl space liners, vapor barriers can come in sizes such as a 20 mil, 16 mil, 12 mil, 10 mil, 8 mil and 6 mil. For a homeowner that doesn’t know much about crawl space vapor barriers, it could become a hassle trying to choose the right one on your own.

The most common crawl space vapor barrier types used is the 20 mil liner and the 12 mil liner. The 20 mil vapor barrier is commonly used on crawl space floors while the 12 mil liner is used on both floors and foundation walls. The size you use ultimately depends on your crawl space.

20 Mil Vapor Barrier

Most 20 mil vapor barriers are used for crawl spaces that will have heavy storage in the encapsulated area. This sized vapor barrier is also used for crawl space floors that have jagged rocks or concrete that can’t come up. If you have a crawl space floor with sharp points, you’ll likely want to go with a 20 mil liner on the floors.

12 Mil Vapor Barrier

The 12 mil vapor barrier is used both on crawl space floors and foundation walls. Let’s discuss the floors first. The 12 mil liner is enough to hold medium foot traffic in the crawl space and medium storage on the vapor barrier. Again, the size you need to use on the floor will have to be determined. If your crawl space floor doesn’t have sharp points, you should be fine with a 12 mil. Most contractors will recommend the 12 mil size for your foundation walls.

Smaller Vapor Barrier Sizes

Can you use a smaller size for your floors and foundation walls? It all depends really, for the crawl space floor, I wouldn’t recommend anything less than a 12 mil liner. The foundation walls are different. You may be able to get away with a 10 mil, 8 mil or 6 mil.

Quality Matters And Here’s Why

Look, there’s a lot of crawl space vapor barrier types out there and choosing the right one can be confusing. On top of all the vapor barrier sizes, there’s also different brands that you have to consider.

The one thing I will highly suggest, do make sure you’re ordering or buying a quality crawl space vapor barrier. While there’s several vapor barriers for the crawl space you can choose from, there’s far less liners that are high quality. The last thing you want is to be back under the crawl space in a year doing an encapsulation project again. It will cost far less to go ahead and get a high quality vapor barrier. You’ll save time and effort ensuring the job is right.