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What Is A Crawl Space & Why Do You Have One?

The crawl space is a small hollow area of a house that offers access to household components such as HVAC equipment, plumbing, insulation, and wiring. Explore the pros and cons of crawl spaces and learn how to solve the problems that may accompany them.

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Most homeowners give little to no thought about the crawl space in their home until they actually need to access it, but there are several things anyone who owns a home should know about these small spaces. Here’s what you should understand about crawl spaces, their uses, and how to solve the problems that may accompany them.

Whether you’re thinking about adding a crawl space to a new build or you need to address issues in your current home, ImproveNet can put you in touch with the right professionals. Speak with a local contractor today.

What Is A Crawl Space?

A crawl space is a narrow, unfinished area of a house that’s designed to be accessed by crawling. Standing about 1 to 3 feet high, crawl spaces often sit between the ground and the first floor of a home. They can sometimes be found in areas of an attic that aren’t tall enough to be used as living space.

What Are Crawl Spaces Used For?

Depending on where they’re located in your home, crawl spaces serve several practical functions.

Adding Elevation

A crawl space can add elevation to a house, which is often helpful for structures located in flood zones. This additional height may prevent water from reaching the ground floor during storms and unusually high tides.

Providing Access For Repairs

Crawl spaces provide easy access to household components such as HVAC systems, ductwork, plumbing, electrical wiring, and insulation. Because crawl spaces typically offer unrestricted access to these essentials, they simplify repairs and installation, often eliminating the need for costly excavations, which can occur when a house sits directly on top of a foundation.

Creating Ventilation

In regions that experience significant rainfall, foundation crawl spaces can provide the ventilation necessary to keep your home dry and free of mold. They can also prevent moisture damage to insulation.

Providing Storage

Whether your crawl space sits beneath the house, under the stairs, or in the attic, it can provide home storage space for seasonal decorations and other items.

What Are Common Crawl Space Problems?

Unfortunately, crawl space foundations are prone to dampness and moisture, which can lead to several common household problems. In fact, buckling floors, bad smells, high energy bills, and even chronic health problems can point to crawl space issues such as these.


Unaddressed moisture issues can lead to wood rot, causing structural issues that threaten the integrity of your home.

Poor Energy Efficiency

During winter months, heat can escape through a poorly insulated crawl space. The result can be cold floors and high utility bills.


Because crawlspaces are dark and undisturbed and often have exterior access, they’re inviting to pests such as:

  • Rodents and other small animals
  • Wasps and hornets
  • Carpenter ants
  • Beetles
  • Termites
  • Crickets

Mold And Mildew

Moisture can create a breeding ground for microorganisms, which can infiltrate your house, leaving you with poor indoor air quality. That can aggravate respiratory conditions such as allergies and asthma.

How Can You Solve Common Crawl Space Problems?

Fortunately, most of the problems associated with crawl spaces are simple to prevent with proper insulation and venting.

Vented Vs Sealed Crawl Spaces

Crawl spaces may be either vented or sealed. Although many modern contractors advocate for sealed or encapsulated crawl spaces, in drier climates it may be possible to successfully vent the area. Vented crawl spaces are also necessary if the space has a bulk water issue or contains atmospheric combustion appliances.

How To Properly Vent A Crawl Space

According to the International Residential Code, at least 1 square foot of screened vent space created from approved materials must penetrate the house’s perimeter foundation for every 150 square feet of the crawl space. This frequency may be reduced by installing an approved vapor barrier over the bare ground of the floor. Ventilation must also be installed near each corner to promote cross-flow of air.

Vented crawl spaces should also include a means of preventing water from coming in from outside.

How To Encapsulate A Crawl Space

If you opt for an encapsulated crawl space, it must be sealed properly to avoid additional problems. Once nearby drainage issues have been solved, your crawl space can be encapsulated in several steps.

  1. Installing an approved vapor barrier on the ground and foundation walls
  2. Insulating the walls
  3. Sealing and insulating the crawl space access door to create an airtight seal
  4. Conditioning the air to eliminate condensation using your HVAC system or by installing a dehumidifier or exhausting air to the outside

How To Insulate A Crawl Space

Insulating the crawl space walls is an important part of encapsulation, and it can significantly improve energy efficiency. Prior to beginning the insulation process, it’s important to eliminate any sources of water. That can be accomplished by regrading the nearby landscape, waterproofing your basement, extending downspouts, or installing a sump pump.

Once your crawl space is dry, insulation can be installed. Be sure to use water-resistant materials such as certain types of spray foam.

How To Build A Crawl Space Foundation

Building a crawl space is similar to building a basement and involves several steps.

  1. Excavating to the proper depth: This includes digging out the main foundation hole and trenches for the footings.
  2. Pouring concrete footings: Before they dry, footings must be reinforced with rebar to meet local building codes.
  3. Shaping walls: Crawl space walls must be formed and reinforced with steel rebar.
  4. Inspection: Newly formed foundation walls must be inspected to ensure they meet building codes.
  5. Pouring concrete for the walls: This should be done all at once.
  6. Removing air bubbles: This is typically accomplished using a concrete vibrator.
  7. Inserting anchor bolts: Bolts are placed along the top of the wall to secure the sill plate.

Getting Started

Whether you're looking to include a crawl space foundation in the home you're building or you need to solve problems with a preexisting structure, it's important to do your research. ImproveNet's crawl space cost guides can help you get started today.

Article Topics

  • Concrete, Brick, & Masonry

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