What's in Your Crawl Space?

·8 min read

You likely know if your home has a crawl space, but what's inside that crawl space may be a mystery. After all, the idea of slithering around a dirt floor and potentially encountering insects, spiders, rodents or even bigger animals may not appeal to you. In fact, it might downright terrify you.

But your crawl space is an important part of your home's structure, and issues that begin in your crawl space can lead to larger issues throughout your house. Follow this guide to crawl spaces to get acquainted with what's under your house and how to spot problems:

[Read: The Guide to Home Renovations.]

What Is a Crawl Space?

A crawl space is a narrow gap between the underside of a house and the ground that provides enough elevation for a person to crawl around.

As the name indicates, a crawl space is not tall enough to stand up in and can be very narrow depending on the property. The minimum crawl space height required by the Federal Housing Administration is 18 inches, but crawl spaces can be taller, often up to 3 feet.

The low clearance combined with potential exposure to mold, pests or standing water makes a crawl space unpleasant. For home inspectors, who examine the crawl space to look for issues with the structure and systems of a house, it's a hazard. "It's probably the most dangerous part of our job, maybe even more so than the roof," says Nick Gromicko, founder of the International Association of Certified Home Inspectors, based in Boulder, Colorado.

Crawl Space vs. Slab

When a house is built on a slab, the concrete foundation is poured directly on the ground, and the house is built right on top. Both slab and crawl space have their pros and cons, and one can be favorable over the other depending on climate and the type of home built.

While a house built on a slab won't have the potential for mold growth and moisture issues under the house, a house with a crawl space has a place to run electrical wiring, plumbing and ducts under the house with relatively easy access. Additionally, a house with a crawl space is elevated and less likely to endure flooding.

Crawl Space vs. Basement

A basement provides a home with underground foundation and enough room in the lower part of the house to stand up. Local codes may vary when it comes to basement height, but many require around 8 feet of clearance.

A basement allows for easier access to ducts, wiring and plumbing than a crawl space and can be finished as livable space. In areas with a high water table, however, a crawl space will be seen as the optimal foundation type because of a basement's higher likelihood of flooding.

What's in a Crawl Space?

Here's what you can expect to find in a crawl space:

-- Floor joists. Serving as the ceiling of your crawl space, the underside of the floor of your home is supported by joists, which are solid pieces of wood or steel that run parallel and support the house's structure.

-- Footings. These are concrete blocks that are either buried or partially buried, serving as the base of the raised foundation of the house.

-- Beams and girder. Compared to joists, beams carry more weight and play a more integral role in supporting the structure. A girder is the main beam, often located in the middle of the underside of the floor.

-- Pier. This is a vertical post, column or block that supports the girder or other beams, connected to footing.

-- Vents. A crawl space should have ventilation to allow air to escape from under the house.

-- Insulation. Either located between floor joists or along the walls of the crawl space, insulation keeps your home more energy efficient.

-- Plumbing. A crawl space is the perfect place for plumbing to run under floors and allows for fairly easy access when a repair is needed.

-- Electrical wiring. Similar to plumbing, electrical wiring running under your floors makes it easy for an electrician to access.

-- Ducts. Your HVAC system can run ducts in the crawl space to avoid placing ducts above the ceiling or having them exposed in the interior of the house.

-- Vapor barrier. A vapor barrier is often white and looks like a plastic sheet covering the entire crawl space, making it appear cleaner and reducing the risk of moisture and mold growth. Many crawl spaces don't initially have vapor barriers; they're often installed only after moisture issues arise.

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Crawl Space Access

Every closed crawl space should have an access door. It's often located outside and at the back of the house. While the door is meant to keep wildlife or pests out of your crawl space, there's a chance they may be down there anyway, so be prepared.

"What we do when we first go down there and open the door is wait, because something could come out," says Deora Pollock, owner of Crawl Space Ninja in the East Raleigh and Durham, North Carolina, area.

For that reason and for the fact that crawl spaces have dirt floors and could have moisture issues, you should cover up before going in. Pollock recommends Tyvek coveralls with a hood, combined with eye protection and a filtered face mask for better breathing in case there's mold growth or sewage in the crawl space.

Common Crawl Space Problems

Here are some of the most common issues involving your crawl space that you may encounter:

-- Moisture. High humidity, flooding from excessive rain or condensation from pipes can lead to elevated moisture in the crawl space. Because moisture leads to mold, it's a problem that will only get worse over time.

-- Plumbing leak. If you have a damaged or improperly sealed pipe, a leak can cause elevated moisture levels in your crawl space. "If there's a leak in your crawl space, you may not know about it for decades," Gromicko says. A consistent water or sewage leak can lead to widespread damage of insulation, flooring and anything else down there. Not to mention the consistent smell of sewage would be unpleasant.

-- Mold. The musty smell in your home may be penetrating from mold growth in your crawl space and can cause ongoing health problems.

-- Structural damage. A house with a raised foundation won't develop the same issues as a slab home when the ground shifts, but a damaged footer or broken beam in the crawl space can lead to sloping floors, cracks in the walls or other structural damage.

-- Insulation. A complete lack of insulation in your crawl space means heat in winter and cool air in summer are escaping through the crawl space, which drives up your utility bills. Wet or moldy insulation is ineffective. Insulation between the floor joists won't help your plumbing or ducts in the event of a cold snap. Instead, Pollock says insulating the walls of the crawl space is a more effective method for protecting a closed crawl space.

-- Termites. The FHA guidelines for home appraisals instruct appraisers to check areas for possible evidence of termite infestation, including in the crawl space. While a termite infestation is likely a bigger issue affecting more than just your crawl space, the exposed joists and subfloor of a crawl space make it easier to spot than in other parts of the home.

-- Rodents or other animals. It's not unheard of to find mice, rats or even the occasional cat or opossum in a crawl space. In the worst-case scenario, unwanted animals not only make the crawl space their home, but gain access to the inside of your house as well.

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Crawl Space Repair

Any of the issues listed above could require crawl space repair. But because of the problems and how pervasive they may be, the work needed can be extensive.

Different companies specialize in moisture issues, structural repair and pest control, among other details. However, it's important to shop around like you would with any contractor -- check references, verified reviews and complaints through the Better Business Bureau.

Mike Pollock, Deora Pollock's husband and vice president of franchise development for Crawl Space Ninja, notes that much of the business the company does across the country includes fixing the poor work of previous contractors.

A homeowner in Knoxville, Tennessee, dealt with persistent musty smells in her home for about six months after having a contractor repair moisture problems in the crawl space before contacting Crawl Space Ninja, Mike Pollock says. "The previous contractor did an absolutely horrible job. It was very clear as to why she has smells in her home," he says. "We had to demolish everything that the previous contractor had done."

Whether you need foundation repair, encapsulation with a vapor barrier, mold remediation, new insulation or all of the above, expect the total cost to climb fast. HomeAdvisor reports the typical range for crawl space repair and cleaning is between $1,500 and $15,000. When it comes to issues of major mold as in the Knoxville homeowner's crawl space, the price can be closer to $22,000, Mike Pollock says.

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