How to Reduce Moisture in a Crawl Space

Moisture buildup can cause a lot of problems. Excess moisture can rot materials like wood, and will rust metal. Moisture buildup combined with poor ventilation is an ideal breeding ground for mold. There are a few options for keeping a crawl space dry, depending on the severity of the problem and how much you can spend. Light moisture problems can be fixed by circulating the air in the crawl space and running a dehumidifier. If the problem is a persistent one, you may need to add a moisture barrier to your crawl space to prevent moisture from building up in it.

Pulling Moisture out of the Air

Moisture and poor ventilation cause Mildew infestations!

Step 1

Ventilate the crawl space, and check for standing water.  If your crawl space doesn't have vents, you can ventilate it by opening it up to the rest of the house and setting up a fan in it to circulate the air.

Step 2

Dry any pools of water with a towel. 

Step 3

Run a dehumidifier in the crawl space.  Commercial grade, crawl space dehumidifiers are a bit pricier than the standard home dehumidifiers, but will be less likely to be damaged by exposure to a great deal of moisture.

Installing a Vapor Barrier

Step 1

Roll strips of plastic moisture barrier from one end of the crawl space to the other, with 6 inches of the barrier going up along each wall.  The strips of moisture barrier should be placed side-by-side so that they overlap; the overlapping portion should be sealed with seam tape.

Step 2

Fasten the barrier to the wall either by nailing it or with construction staples. 

Step 3

Stake down the moisture barrier with landscape fabric stakes.  This will secure the barrier to the ground and allow water to drain when it does get in to your crawl space.

Things You Will Need

  • Fan
  • Dehumidifier
  • Moisture barrier
  • Hammer or construction stapler
  • Nails or construction staples
  • Seam tape
  • Landscape fabric stakes

Photo Credits

  • antique paper - colour series image by pdtnc from Fotolia.com