Crawl Spaces

What does a crawl space do?

Homes that do not have basements or cement slab foundations usually have a crawl space to provide an access point for electrical, plumbing, ventilation and gas hook-ups within the home.  A crawl space makes it possible to reach these areas when repairs, installation or other services are necessary.  

Residential housing that is located in prominent flooding zones often use the crawl space as a means of providing the home with extra space should these events occur.  The water will fill into the crawl space before invading the home.  Special regulations and codes are required by federal organizations for building crawl spaces in these locations of the United States.

While it is not possible to include a crawl space within the living space figured for the home as you could with a basement, it is still possible to utilize a crawl space for storage of smaller items. 

While you can’t convert a crawl space into a useful living area like you can with a basement, the area can still be used to store smaller outdoor items. However, it’s recommended not to use your home’s crawl space as a storage area if you have mold, moisture or pest problems in the area. It’ s also a good idea to avoid storing any chemicals or other potentially harmful items in a crawl space.

Moisture in crawl spaces

If you live in an area that experiences hot, humid weather, your home’s crawl space might be at high risk for damage caused by excessive moisture accumulation. This problem is especially common in older homes that feature vented crawl spaces rather than sealed crawl spaces.

With these types of set-ups, if there isn’t a moisture barrier or encapsulation system in place, hot, humid area enters the crawl space. When it comes in contact with floorboards or other surfaces that have been made cooler by air conditioning, the humid air condenses to form moisture.

This moisture accumulation can threaten the structure of your home. When exposed to excessive moisture, structural wood elements such as beams or piers can become weakened due to rot.

Homeowners can avoid structural damage by installing a vapor barrier on vertical surfaces and the floor, a dehumidifier and humidity-monitoring system. Excessive moisture in older vented crawl spaces is particularly prevalent in the late spring and summer in moderate climates. Other moisture mitigation techniques include sealing any passive ventilation openings, adding drains to lead pooled water to a sump pump or outdoors and installing force-air ventilation systems.

Crawl space experts say sealing a crawl space usually costs about $5,500 on average, but the costs can easily range from $1,500 to $15,000 depending on the issues and the size of the home.

Other crawl space problems

Mold, mildew and fungus

If a moisture problem within a crawl space isn’t addressed properly, over time, the moisture can produce conditions that are a prime breeding ground for mold, mildew and other microorganisms.  If the air in the crawl space infiltrates the home, mold spores, mildew and other potentially harmful microorganisms such harmful bacteria can do so as well. 

Exposure to mold or fungal spores can irritate home occupants who suffer from asthma, respiratory ailments or allergies, and also cause infections, skin rashes and other medical conditions. 


If not properly sealed against intrusion, rodents, insects and other pests can enter the crawl space. In fact, the warmth and moisture associated with a ventilated, unimproved crawl space can make them particularly attractive to these types of animal invader.

Animal pest in particular can cause air quality problems and health hazards from their droppings. Both animals such as raccoons and insects such as termites may also actively cause damage to structural elements and systems such as HVAC ducts or electrical wiring.

Poor insulation

The energy efficiency of home’s heating and cooling equipment is also cause for concern in older homes with poorly constructed or unimproved crawl spaces. If a vented crawl hasn’t been sealed or insulated, outside air that’s hotter or cooler than the home’s indoor air may come in contact with the underside of floorboards within the area.

Via heat transference through the floorboards, the outside air may increase the indoor air temperature during spring and summer months, reducing the cooling capacity of an air conditioning system, or decrease the indoor air temperature during cooler months, reducing the heating capability of a furnace or other heating system.

Installing insulation along with a vapor barrier, as well as sealing ventilation that allows outside air to enter a crawl space can reduce these energy inefficiencies.

Selecting a contractor

If you’re concerned your crawl space may have problems, contact a contractor that specializes in crawl space encapsulation, moisture prevention or mold remediation. If you believe your crawl space may be infested by pests, rodents or other animals, a pest control or animal exclusion professional should be called in first before any improvement work commences.

Unfortunately, due to the difficulty of accessing a crawl space, some unscrupulous contractors have been known to use scare tactics, such as trying to convince a homeowner repairs need to be made immediately, to trick homeowners into purchasing unnecessary services.

Protect yourself financially by doing your homework before hiring a contractor. Check Angie's List to see what other homeowners in your area are saying about their experiences with crawl space contractors. If possible, get at least three companies to provide estimates or bids on the work. Ask for and check references from previous customers, check a contractor’s licensing status if applicable in your area and always make sure to hire a firm that carries adequate insurance.

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