Crawl space vapor barrier replacement
The plastic on the ground under your house does more work than it looks like. When it fails, moisture from the soil moves straight up into the framing.
Bare dirt gives off water vapor constantly, more so on the poorly drained clay soils found on some lots around Rocky Mount. A vapor barrier, or ground cover, slows that down. In many older houses the original plastic was thin, never fully covered the ground, or has been ripped apart over the years by plumbers, HVAC techs, pest control crews and the occasional animal.
Vapor barrier or full encapsulation?
A new ground cover in a crawl space that stays vented is a smaller job than encapsulation. It cuts down on moisture coming from below but does nothing about humid summer air coming in through the vents. If the ducts sweat and the insulation sags every summer, the ground cover alone probably won't fix it. In that case, ask about closing the crawl space. If the musty smell is mild and the main issue is exposed or torn plastic, a replacement may be enough.
What makes a ground cover last?
- Coverage of the whole floor, not just the middle
- Seams overlapped and taped rather than just laid next to each other
- Edges brought up the foundation wall and piers and fastened
- Material tough enough for people to crawl across without tearing it
For closed crawl spaces, the North Carolina Residential Code sets the minimum at 6-mil polyethylene or an equivalent. Thicker, reinforced liners are widely used because they hold up better to foot traffic.
Signs the old one has failed
- Large areas of bare soil showing
- Plastic that's brittle, shredded or bunched against one wall
- Water sitting on top of the plastic after rain
- Droppings, nesting or burrows under the edges
Is a permit needed?
Laying a new ground cover in a crawl space that stays vented generally isn't the kind of change the state's closed-crawl-space interpretation covers. Sealing the vents is. If the plan touches insulation, the City of Rocky Mount's permit list includes insulation as permitted work. Ask the company to confirm with the local inspections office.
What affects the price?
- Crawl space size and clearance
- Liner thickness and how far it runs up walls and piers
- Removal of the old plastic and any debris
Pricing comes from the crawl space company after someone has been under the house, measured it and seen what's there. We don't give prices, and a figure offered over the phone before that visit is a guess, not a quote.
Where we connect you with help
Common questions
How thick should a crawl space vapor barrier be?
The NC Residential Code minimum for a closed crawl space is 6-mil polyethylene or equivalent. Heavier reinforced liners are common because they resist tearing.
Will a new vapor barrier stop my ducts from sweating?
Probably not by itself. Sweating ducts usually come from humid outdoor air through the vents. Closing the crawl space and controlling humidity addresses that.
Related services
- Crawl space encapsulation
- Dehumidifiers and moisture control
- Crawl space repair and cleanup
- Sagging floor support
More background: Rocky Mount crawl space guide.
Damp smell, sweating ducts or a floor that's started to dip?
Call and we'll put you in touch with a crawl space company that works in your part of Nash or Edgecombe County.