How to Cover a Crawl Space

  • 48-96 hours
  • Intermediate
  • 500-800
What You'll Need
4 millimeter (or thicker) vapor barrier or plastic sheet
Duct tape
1 1/2-inch thick insulation (moisture safe)
Wet and dry vacuum
Respirator mask
Gravel or sand

The crawlspace in your home is designed to allow workers to access utility equipment in your home, such as electrical wires, plumbing, and duct work. Many builders do not seal the crawlspace against moisture. When moisture enters the crawl space, vapors which can cause mold and mildew to form are released.

With the crawlspace unsealed, you will also find that air will circulate from within the crawlspace all over the home. It can also allow hot and cool air to escape the home so that your heating and cooling expenses escalate. Follow these steps to properly cover your crawlspace.

Step 1 - Clear the Crawl Space

Everything that is inside the crawlspace should be removed from it, especially pieces of wood or cardboard. The dampness of the crawlspace will cause these materials to grow mold and mildew. Also want to remove any water that may have collected in the space.

WARNING: Standing water can breed insects and other potentially harmful bacteria. Always wear a protective mask when doing this. If there are visible signs of mold or mildew make your mold killer by mixing 1/3-cup of detergent with 1/2-gallon of bleach and 2-gallons of warm water. Pour the mixture into a spray bottle and apply it to all areas of the crawlspace.

Step 2 - Placing the Vapor Barrier

Lay the plastic sheet or vapor barrier twice. Take the sheets into the crawlspace and lay them over the dirt floor. Cover the entire area. As you spread the sheet, press it to remove any trapped air. With this first layer placed, you can now cut it to lay a second layer.

As you place it, also place bricks to keep it in place. Use the duct tape to seal the seams of the plastic sheeting. There should be overlap throughout the sheet, which makes it easier to seal. Once it is sealed, place a layer of gravel or sand over the plastic to absorb escaping moisture as well as to stop drips from above.

Step 3 - Insulate the Foundation Walls

In order to keep moisture out, you should cover the walls of the foundation with insulation. Doing so will stop the concrete from sweating and creating moisture. It is not necessary, but you can add a layer of vapor barrier over the insulation for added protection.