Crawl space encapsulation in Little Rock

Encapsulation turns a vented crawl space into a closed one. Instead of letting outdoor air wash through the foundation vents, the space is lined, sealed and given its own way to get rid of moisture. In Little Rock, where summer air under a house can sit near its dew point for weeks, that is often the difference between a dry subfloor and moldy joists. It is also a real construction project with code requirements, so it helps to know what you are buying.

What an encapsulation job includes

• A sealed ground liner. Plastic sheeting covers every bit of exposed dirt, with seams overlapped and taped, run up the foundation walls and piers and fastened there. The Department of Energy's Building America guide calls the ground cover a capillary break and vapor barrier that keeps ground moisture and soil gases out, and says it belongs in vented and unvented crawl spaces alike. Many encapsulation liners are heavier than the 6-mil minimum in that guide; ask for the thickness in writing.
• Vents and openings closed. Foundation vents, gaps around pipes and wires, and the access door are sealed so humid outdoor air stops coming in.
• Insulation moved or replaced. Sagging, wet batts between the floor joists usually come out. In a closed crawl space the foundation walls are often insulated instead of the floor.
• A way to manage the air. Once it is sealed, the space still has to be kept dry. That is the part Arkansas's code speaks to directly.

What Arkansas code says about unvented crawl spaces

Arkansas builds to the Arkansas Fire Prevention Code, whose residential volume is the 2021 International Residential Code with state amendments. Section R408.3 covers unvented crawl spaces, and the Arkansas version differs from the national model code:

• Exposed earth is covered with a continuous Class I vapor retarder, joints overlapped 6 inches and sealed or taped, edges run at least 6 inches up the stem wall and sealed to it.
• The space gets a mechanical exhaust and supply air system. Exhaust has to be at least 0.02 cfm per square foot of floor area (about 30 cfm for a 1,500 sq ft crawl space) and controlled automatically, running when humidity in the space tops 60 percent, or when the outdoor air is drier than the crawl space air but not below 32°F.
• Using the crawl space as a supply air plenum is prohibited.

The national model code also lists a dehumidifier as a stand-alone option; the Arkansas text doesn't. Plenty of sealed crawl spaces around Little Rock still run a dehumidifier for humidity control, but ask the contractor how their design meets the state's exhaust and supply air requirement, and whether your city wants a permit. More on equipment in crawl space dehumidifiers.

When a vapor barrier is enough

Not every damp crawl space needs to be sealed. A plain ground cover with the vents left open can do the job when:

• Water isn't getting in. Gutters, downspout extensions and grading are fixed, and the dirt is dry a day after a hard rain.
• A hygrometer left under the house in July stays under about 60 percent.
• Ducts and pipes in the crawl space aren't sweating, or sealing and insulating them stops it.

If readings stay in the 70s and 80s all summer even with a good ground cover, that is the case for encapsulation. The Little Rock humidity calendar shows why: July dew points average about 71°F, warmer than the joists and ducts under most houses.

What drives crawl space encapsulation cost

We don't set prices, and quotes vary a lot from house to house. These are the things that move the number:

• Floor area and wall height. Liner is priced by the square foot, and taller foundation walls mean more liner and more wall insulation.
• Access and clearance. A 16-inch crawl space with ductwork in the way takes far more labor than one you can kneel in.
• Water management. Grading or drainage work outside, an interior drain, or a sump pump where water collects after storms.
• Mold cleanup first. Joists and subfloor with existing growth have to be cleaned before they are sealed in. See crawl space mold and what drives mold removal cost.
• Tear-out. Old insulation, torn plastic, debris and anything organic left from construction have to come out.
• The air system. Exhaust fan, supply air, a dehumidifier, the electrical circuit and a condensate drain for it.
• Ductwork. Sealing or replacing leaky ducts in the space, which may be a separate HVAC job.

Before you sign

• Ask for moisture readings on the joists and humidity readings in the space, before and after.
• Get the liner thickness, how far it runs up the walls, and how seams and piers are sealed, in writing.
• Ask which Arkansas R408.3 air method they use, who services it, and what the upkeep costs.
• Make sure existing mold is cleaned, not just covered.

Call and we'll connect you with a local professional who does crawl space work around Little Rock, North Little Rock, Conway and Benton.