Crawl space vapor barriers in Hattiesburg
A good ground cover is the cheapest way to cut the moisture coming up from the soil under a Pine Belt house.
Bare dirt under a house is a constant source of water vapor. In a wet climate like Hattiesburg's, where a typical year brings more than 60 inches of rain, the soil under a crawl space can stay damp for weeks at a time. A ground vapor barrier, usually polyethylene sheeting, blocks that moisture from evaporating into the crawl space air.
Why does the old one need replacing?
A lot of older Hattiesburg homes never had a ground cover. Newer ones often got a thin sheet of plastic that's since been torn by plumbers, HVAC techs, cable installers and pest control crews crawling over it. Plastic that's bunched up, shredded or covered in dirt isn't doing much.
What the code says about vented crawl spaces
Under Section R408 of the International Residential Code, a vented crawl space normally needs 1 square foot of vent opening for every 150 square feet of floor area. When the ground is covered with an approved Class I vapor retarder, that can drop to 1 square foot for every 1,500 square feet. In other words, the code treats a ground cover as a major moisture control.
What makes a good installation?
- The ground cleared of debris, sharp rocks and old plastic
- Seams overlapped generously and taped
- Edges carried up the foundation walls and around piers
- A material thick enough to survive the next service call
- Any standing water problem fixed before the plastic goes down
Barrier or full encapsulation?
A ground barrier deals with moisture from below but leaves the vents open to humid summer air. If your ducts sweat or the house still smells musty after the ground is covered, closing the crawl space may be the next step. Read about encapsulation.
Signs your vapor barrier has failed
- Exposed dirt showing through tears or gaps
- Water pooled on top of the plastic
- Plastic pulled loose from the walls or never attached
- A musty odor even though "there's plastic down there"
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
How thick should a crawl space vapor barrier be?
The IRC's unvented crawl space section is built around a continuous Class I vapor retarder, and 6-mil polyethylene is a common minimum. Many companies offer thicker reinforced liners that hold up better to foot traffic.
Will a new vapor barrier fix a musty smell?
Sometimes. If most of the moisture is coming from the ground, yes. If humid air through the vents is the bigger problem, you may also need to close the crawl space.
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.