Crawl space vapor barriers in Dothan
Covering bare dirt is the simplest way to cut down the moisture rising into a Wiregrass crawl space.
Soil holds water, and a bare dirt floor under a house releases that water into the crawl space air day after day. A vapor barrier, a sheet of polyethylene or a reinforced liner laid across the ground, stops most of it. It's often the first and least expensive crawl space fix.
What the code says
For a vented crawl space, Section R408 of the International Residential Code, which Dothan enforces in its 2021 edition, generally requires 1 square foot of vent opening for every 150 square feet of crawl space. When the ground is covered with a Class I vapor retarder, the minimum drops to 1 square foot per 1,500 square feet. The code treats a ground cover as doing much of the work that vents once did.
Why replace what's already there?
Plenty of Dothan homes never had a ground cover. Others have thin plastic that's been shredded over the years by pest control, plumbing and HVAC visits, or that only covers part of the floor. Plastic with gaps, rips and dirt on top is barely helping.
What a good install looks like
- Old plastic and debris removed, sharp objects raked out
- Seams overlapped and taped, not just laid side by side
- Edges carried up the foundation wall and fastened
- Piers wrapped or sealed around
- A material tough enough for future service calls
Is a vapor barrier enough?
It handles moisture from the ground. It doesn't stop humid summer air coming through open vents. If your ducts still sweat or the smell lingers after a new ground cover goes in, consider closing the crawl space. Read about encapsulation.
Signs your vapor barrier isn't working
- Bare soil visible through holes or gaps
- Water collecting on top of the plastic
- Plastic that stops short of the walls
- Persistent musty smell despite a ground cover
The crawl space company sets the price after it has inspected and measured the space under your house. We don't quote prices, and any figure you hear before someone has looked underneath is a rough guess.
Where we connect you with help
Common questions
Can I install a crawl space vapor barrier myself?
Alabama law doesn't stop homeowners from working on their own residence. It's dirty, cramped work, though, and seams and edges need to be sealed properly to be effective.
Do I still need vents with a vapor barrier?
In a vented crawl space, yes, though the IRC allows much less vent area when the ground has a Class I vapor retarder. A fully sealed crawl space needs other moisture control instead.
Related services
More background: Dothan crawl space guide.
Musty air, wet insulation or a floor that's lost its footing?
Call and get connected with a crawl space company that works in Dothan and the Wiregrass.