Crawl space vapor barrier installation
Bare dirt under a house releases a steady stream of water vapor. A ground cover is the simplest place to start.
A vapor barrier, also called a vapor retarder or ground cover, is a plastic sheet laid over the soil in a crawl space. It slows the moisture that would otherwise rise from the ground into the framing and insulation. In many older Valdosta houses the original plastic is thin, torn, pushed into piles by years of plumbers and cable installers, or missing altogether.
Vapor barrier or full encapsulation?
They aren't the same job. A vapor barrier on its own covers the ground in a crawl space that stays vented. Encapsulation goes further: the vents are closed, the liner runs up the walls and is sealed, and the air is dried. Southface's guide to the Georgia code notes that the IRC requires a vapor retarder in both vented and unvented crawl spaces unless the space is "highly vented," while the energy code focuses on unvented ones. Which approach suits your house depends on how wet it gets, the condition of the framing and your budget.
What makes a good installation?
- Debris and sharp objects cleared before the liner goes down
- Generous seam overlaps, taped or sealed
- Sheets lapped up the foundation walls and around piers
- A liner tough enough to survive people crawling on it
- Any water problem handled first, so the plastic isn't holding a puddle
When a liner alone won't solve it
If water collects on top of the plastic after storms, ducts are dripping with condensation, or wood is already soft, a ground cover is only part of the fix. Ask the company to check moisture levels in the framing and look at gutters and grading before deciding on the scope.
Pricing comes from the crawl space company, after someone has been under the house and measured it. We don't quote prices, and a number offered before anyone has looked at the space is only a guess.
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Common questions
How thick should a crawl space vapor barrier be?
The Georgia energy code field guide gives 6-mil polyethylene as an example of a Class I vapor retarder. Many installers use heavier, reinforced material because it holds up better to foot traffic and crawling.
Can I put down new plastic myself?
Many homeowners do for a simple vented crawl space. Clear debris, overlap and tape the seams, and run the plastic up the walls. If there's standing water or damaged wood, have a company look first.
Related services
More background: Lowndes County crawl space guide.
Musty smell, droopy insulation or a floor that gives underfoot?
Call and a crawl space company that works in Lowndes County will take a look under the house.