Crawlspace odors can spread to the rest of the home. Many houses are built with a crawlspace between the ground and the first floor. The builders do this so that they can have easy access to ductwork, electrical wiring, and other home utilities.
You will not find this type of crawlspace in a home that has a basement. Unfortunately, these crawlspaces typically have a dirt floor that often gets wet. This moisture can cause mold and mildew to appear, subsequently creating an odor.
Step 1 - Assess the Problem
There are possible several causes of crawlspace odor. Investigate the crawlspace directly. A metal or wood door should be present, and you should be able to close it tightly. If it is not secure, crawlspace odors can escape into the home.
If it is a dirt floor, assess the moisture level. If too much water vapor is entering the crawlspace, it can create conditions which are suitable for mold and mildew. The same applies to concrete floor crawlspaces.
Step 2 - Dirt Floor Crawlspaces
Dirt floor crawlspaces are the most common. In order to prevent a crawlspace odor from developing, cover the dirt floor with a tarp. Weigh them down with cinder blocks to create a tight seal over the dirt. The tarp prevents water vapor from entering the crawlspace. Mix up a solution of 3 parts water to 1 part bleach. Take the solution inside the crawlspace and scrub the walls. Doing so kills the mold. Make sure you wear a mask and gloves. To further protect against odor, install insulation between the joists of the floor over the crawlspace and add plastic sheeting to the door.
Step 3 - Concrete Floor Crawlspaces
Many homeowners with concrete floor crawlspaces use them as storage areas, which can be both good and bad. Cardboard and other celluloid materials become moldy and give off a mildew odor when left in moist environments.
Remove such materials and scrub the walls and floors with diluted bleach. Use a wet and dry shop vacuum to remove any standing water and a push broom to get to the back areas. Insulate the floor overhead and place a dehumidifier in the crawlspace. Doing so helps dry the water inside the crawlspace and will keep water vapor out of the air.