A crawl space vapor barrier is a sheet of polyethylene laid over the dirt floor so that moisture in the soil does not evaporate into the crawl space. It is the cheapest moisture fix under a house, and it is easy to overpay for, because the same word covers a thin sheet laid loose on the ground and a sealed system that turns the crawl space into a closed one.
What the published ranges say
The headline range further down this page is the one figure the site carries for a whole floor-only job in North Carolina, and it is per home. The detail rows break that down.
- Installed, by liner thickness. CrawlSpaceCosts.com’s 2026 vapor barrier guide puts installed cost at $0.50 to $1.00 per square foot for 6 mil plastic, $1.00 to $1.75 for 12 mil reinforced, and $1.50 to $2.50 for 20 mil. The same guide puts a floor-only 12 mil job on a 1,000 sq ft crawl space at $1,200 to $2,500, in line with the North Carolina headline range.
- A higher national figure. HomeGuide puts installation at about $2 to $4 per square foot, so a quote above the detail rows is not automatically out of line.
- The liner itself. HomeGuide prices a 12 mil reinforced liner at $0.50 to $0.60 per square foot of material and a 20 mil liner at $0.60 to $0.70. On most jobs the material is the smaller part of the bill; labor, sealing and anything that has to come out first make up the rest.
No source publishes a Triangle-specific per-square-foot rate, so the per-foot figures here come from national and statewide guides. How the cost figures are built explains what was and was not done to them.
What moves the price
- Floor area. Most quotes are built on it, and per-foot pricing eases a little on bigger floors.
- Thickness and reinforcement. 6 mil polyethylene is the code minimum where a ground vapor retarder is required; 12 mil and 20 mil reinforced liners cost more and hold up far better under foot traffic.
- Floor only, or a strip up the wall. In a vented crawl space the barrier does not have to go up the wall. Carrying it partway up and fastening it there adds material and labor.
- What has to come out first. An old torn liner, fallen insulation or construction debris is bagged and hauled out before the new one goes down.
- Piers, pipes and obstructions. Every pier the liner is cut around and taped to adds time.
- Clearance. A low crawl space with a small access is slower work for everyone.
- Water. A liner laid over ground that floods after rain hides the water rather than fixing it. If the floor is wet, drainage comes first and is priced separately.
Vapor barrier or encapsulation?
A vapor barrier on the floor of a vented crawl space stops moisture rising out of the soil. Encapsulation also seals the barrier to the walls and piers, closes the vents and dries the air with a dehumidifier, and in North Carolina it needs a building permit. It costs several times as much - see what encapsulation costs in the Triangle.
The cheaper option is sometimes the right one. If summer humidity in the crawl space drops to a safe level once the floor is covered, the barrier was enough. If readings stay high, or ducts keep sweating, the moisture is coming in with the outside air, and only closing the space changes that. Vapor barrier or full encapsulation? walks through the test.
What a quote should list
A vapor barrier quote that can be compared with another one names:
- the square footage it is priced on;
- the liner thickness and whether it is reinforced;
- whether it is floor only or carried up the walls, and how far;
- how seams and piers are sealed;
- removal and disposal of anything already down there, as its own line;
- what happens if they find standing water or damaged wood once they are under the house.
The bid checker lists what any written crawl space quote should specify, and the page on crawl space vapor barrier installation in Raleigh covers the work itself.
About these numbers
Every range on this page names its source and the date it was last checked. None is a quote, a bid, or a price any Triangle homeowner was actually charged. Only someone who has looked under your house can give you the number that applies to it - request a free inspection and we will follow up to schedule one.
Prices on this page are general ranges gathered from published sources, not a quote. What a job actually costs depends on the specifics of the job and who does the work. Only a quote from a qualified contractor who has seen the job is a real price.
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