DIY 101: How to Choose Crawl Space Vapor Barrier

DIY 101: How to Choose Crawl Space Vapor Barrier

Encapsulating your home’s crawl space is a pretty big job. It’s not for beginners, but for DIYers with solid experience under their tool belts. Encapsulation uses several different components to achieve constant low humidity, prevent moisture from reaching vulnerable surfaces such as floor joists and subfloor, and to let any water or moisture that gets in back out again.

What Is It?

Vapor barrier is a low-permeability high-density polyethylene plastic film. You may have seen houses being wrapped or roofs getting a vapor barrier before the shingles go on. It is also very important when keeping a crawlspace high and dry. Not many construction companies doing new homes do anything to the crawlspace, but it’s essential to keep moisture away from the foundation of the house and out of areas.

Your DIY crawl space vapor barrier should be at least Six mils thick though 20 mil is the most commonly recommended. For reference, one mil is the thickness of a sheet of printer paper, and the most commonly used plastic grocery bag is .5 mil thick – so it would be 12 grocery bags to equal six mils thick vapor barrier and 40 grocery bags to equal 20 mils.

Is It Safe?

Federal standards govern the amount of outgassing that is acceptable in exterior building materials. For this reason, it is important to use only materials that are intended for the job at hand. When you’re shopping for a DIY crawlspace vapor barrier, don’t go cheap or use a different type of barrier than the one intended for the job.

Working with Professionals

Even an experienced DIYer needs pro tips from time to time. Before starting your job contact a company that specializes in crawl space encapsulation and have your job site professionally assessed. You don’t want to miss any big issues like drainage or foundation damage that can make all that work and all that effort go for nothing.