Crawl Space Vapor Barrier Installation
A crawl space vapor barrier costs $1,200–$4,000 installed. Compare 6- to 20-mil liner prices, roll counts, code laps, and quotes from local pros.
- Full encapsulation typically $5,000–$15,000, average $5,500 (Angi)
- Vapor barrier installed $2–$4 per sq ft (HomeGuide)
- Dehumidifier installed $1,000–$3,000 (HomeGuide)
- Free quotes from independent local contractors
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Typical national cost$5,000 – $15,000Cost guide →About Crawl Space Vapor Barrier Installation
A vapor barrier is the plastic sheet laid over a crawl space's dirt floor so ground moisture can't evaporate into the space. On its own it's the cheapest moisture fix: HomeGuide puts installation at $1,200–$4,000 and Angi at $1,000–$3,000. Material alone runs $0.30–$0.70 per square foot depending on thickness.
Thickness matters for durability, not the code minimum. North Carolina accepts 6-mil polyethylene with 12-in laps (R409.2.1). The IRC asks for a Class I vapor retarder with sealed 6-in laps carried 6 in up the wall (R408.3). Thicker 12- to 20-mil liners resist tearing from foot traffic and service work. A floor-only barrier in a vented crawl space is not encapsulation; the encapsulation page explains the difference.
Common Jobs We Route
- Floor-only barrier in a vented crawl space ($2–$4/sq ft installed)
- Full floor-and-wall liner as part of encapsulation
- Replacement of a torn or flattened old barrier
- Reinforced liner with a concrete skim coat (NC R409.2.3 allows a 2-in unreinforced concrete surface over the barrier)
What Affects the Price
Providers quote their own work — these are the factors that consistently move the number.
- Mil and roll count: per 1,200 sq ft roll, 6-mil $360–$420, 12-mil $600–$720, 20-mil $720–$840
- Floor-only vs walls too (wall area = perimeter × height)
- Seam taping and pier wraps; seam tape about $50/roll
- Debris removal and grading first (NC R409.12 requires vegetation and organic material removed)
Cost Guides
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Crawl Space Vapor Barrier Installation FAQs
What thickness should a crawl space vapor barrier be?
NC's minimum is 6-mil polyethylene; the IRC specifies a Class I vapor retarder. Thicker liners cost more ($0.60–$0.70/sq ft for 20-mil vs $0.30–$0.35 for 6-mil) and hold up better.
How much vapor barrier do I need?
Floor area, plus wall area if you're lining walls, plus extra for laps. The calculator does the math in 1,200 sq ft rolls.
Can I install a vapor barrier myself?
Many owners do. The calculator lists materials. Code laps and, in NC, low-spot drains still apply.
Is a vapor barrier the same as encapsulation?
No. Encapsulation also seals vents and adds a drying method; a floor barrier can be one step of it.
Crawl Space Vapor Barrier Installation by Area
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