Crawl space encapsulation in Hattiesburg
Encapsulation closes off a damp, vented crawl space from the humid outdoor air and the wet ground. Here's what it involves in the Pine Belt.
An encapsulated crawl space, which the building code calls an unvented crawl space, is sealed instead of open to the outdoors. The foundation vents are closed, the ground is covered with a continuous vapor retarder that's sealed to the walls, and something is added to manage humidity, because a sealed space with no moisture control can simply trap the dampness.
What does the code ask for?
Hattiesburg lists the International Residential Code (IRC) as its residential building code. Section R408.3 of the IRC allows a crawl space without vents when the exposed earth is covered with a continuous vapor retarder, the joints overlap by 6 inches and are sealed or taped, and the edges run at least 6 inches up the stem wall and are sealed to it. It also requires a way to handle moisture, such as continuous exhaust ventilation or a conditioned air supply at 1 cubic foot per minute for every 50 square feet of crawl space floor. Newer editions also list a dehumidifier sized to remove 70 pints a day for every 1,000 square feet. Thicker, reinforced liners than the minimum are common.
How does a typical job go?
- Inspection. Looking for standing water, wet or damaged wood, plumbing leaks, pest activity and the state of the insulation.
- Water first. Gutters, downspout extensions, grading or an interior drain and sump if water gets in. Sealing a space that floods just holds the water in.
- Cleanout. Hauling out old plastic, fallen insulation and debris.
- Air sealing. Closing vents, the access opening and gaps around pipes, wires and ducts.
- Liner. Laid over the ground with overlapped, taped seams and run up the walls and around the piers.
- Moisture control. A dehumidifier, exhaust fan or a small supply of conditioned air, depending on the house and the HVAC system.
Does it need a permit?
Inside Hattiesburg, the city says a permit is generally needed to repair or alter an existing home, and electrical work for a dehumidifier or fan may need its own inspection. Petal's building department handles building, electrical, plumbing and HVAC inspections there. Unincorporated Lamar County doesn't inspect single-family work. Ask the company which office covers your address and who will pull the permit.
What drives the price?
- Square footage and how much clearance there is to crawl around
- Liner thickness, and whether walls and piers get covered
- How much old insulation and debris has to come out
- Drainage work needed before sealing
- The moisture-control equipment and any electrical work
Pricing comes from the crawl space company after someone has been under the house with a flashlight and a tape measure. We don't quote prices, and a phone estimate before an inspection is only a ballpark.
Where we connect you with help
Common questions
Is encapsulation the same thing as a vapor barrier?
No. A vapor barrier is the plastic on the ground. Encapsulation also seals the vents and walls and adds humidity control, as IRC Section R408.3 describes for unvented crawl spaces.
Can I encapsulate if water gets under my house?
Yes, but the water has to be dealt with first or as part of the same job, with gutters, grading or an interior drain and sump.
Related services
More background: Hattiesburg crawl space guide.
Damp smell, sweating ducts or a floor that gives underfoot?
Call and get connected with a crawl space company that works in Hattiesburg and the Pine Belt.