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Crawl Space Encapsulation

Crawl space encapsulation averages $5,500 ($5,000–$15,000). See what's included, local code rules, permits, and get quotes from independent 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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About Crawl Space Encapsulation

Encapsulation turns a vented, damp crawl space into a sealed one. A pro lines the floor, and usually the walls, with a heavy vapor barrier, seals the foundation vents and gaps, and adds a way to dry the air, most often a dehumidifier. Angi puts the national average at $5,500, within a typical $5,000–$15,000 range. HomeGuide prices it at $3–$10 per square foot of crawl space floor.

Building codes call the result an unvented or closed crawl space, and they spell out what it needs. Under IRC R408.3 the requirements are a continuous Class I vapor retarder with sealed 6-in laps, run at least 6 in up the wall, plus one drying method. North Carolina's own section, R409, asks for 12-in laps, a 3-in termite inspection gap and a drain or sump at each low spot. North Carolina also requires a permit to convert a vented crawl space. Our calculator prices your space and shows which rules apply where you live.

Cross-section of an encapsulated crawl space. A heavy vapor barrier covers the dirt floor with overlapped, taped seams, runs up the inside of the foundation wall to a fastened top edge, and wraps the masonry pier. The foundation vent is sealed shut and the rim joist is sealed with foam. A dehumidifier sits on the liner and drains its condensate into a sump pit at the low spot of the floor.
A sealed crawl space needs a continuous liner with sealed laps run up the walls, sealed vents and rim joists, and at least one drying method (IRC R408.3).

Common Jobs We Route

  • Full encapsulation: floor and wall liner, vents sealed, dehumidifier ($3–$10/sq ft)
  • Basic encapsulation: liner and sealing with no major repairs ($2–$4/sq ft, Angi)
  • Re-encapsulation or liner replacement over an old, torn barrier
  • Closed crawl space conversion with a permit (NC R409) or unvented conversion (IRC R408.3)
  • Encapsulation plus insulation: wall insulation $420–$1,900 for 1,000 sq ft with 3-ft walls
Two crawl space cross-sections compared. Top: a vapor barrier only, a plastic sheet on the dirt floor, with the foundation vent left open so outside air still moves in and out and nothing controls humidity. Bottom: full encapsulation, with the vent sealed, a liner covering the floor, running up the foundation wall and wrapping the pier, and a dehumidifier drying the air.
A vapor barrier only covers the dirt floor. Encapsulation also lines the walls, seals the vents and adds a drying method such as a dehumidifier.

What Affects the Price

Providers quote their own work — these are the factors that consistently move the number.

  • Floor area and wall height (HomeGuide: 1,000 sq ft $3,000–$10,000; 2,000 sq ft $6,000–$20,000)
  • Liner thickness (20-mil material $0.60–$0.70/sq ft vs 6-mil $0.30–$0.35)
  • Prep and repairs found first: cleaning and repairs $500–$8,000
  • Drying method: dehumidifier installed $1,000–$3,500 vs supply-air ducting $450–$2,000
  • Drainage or sump where water stands: drainage $800–$3,000, sump $600–$2,500
  • Labor is 50–70% of the job, per Angi

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Crawl Space Encapsulation FAQs

How much does crawl space encapsulation cost?

Angi's national average is $5,500, with most jobs between $5,000 and $15,000. HomeGuide's range is $3,000–$15,000, or $3–$10 per square foot.

Is a dehumidifier required?

Code requires at least one drying method in a sealed crawl space. A dehumidifier is one option; ducted supply air and an exhaust fan are others (IRC R408.3; NC R409.5).

Do I need a permit?

In North Carolina, yes, to close a vented crawl space, regardless of cost (NC OSFM). Henrico County, VA lists encapsulation as permit work. Elsewhere, ask your building department.

Will encapsulation get rid of mold?

EPA says 'the key to mold control is moisture control' and that existing mold should be cleaned up and the water problem fixed. Encapsulation addresses moisture; mold cleanup is quoted separately. Treat existing mold before sealing, otherwise you trap it in.

What should I ask an encapsulation contractor before I sign?

Ask about liner thickness and whether it runs up the walls and piers, taped seams, how vents and the rim joist are handled, dehumidifier size and drainage, whether mold treatment and old-insulation removal are separate lines, who pulls the permit, what the warranty covers, and for a written, itemized quote and proof of insurance. Our cost guide lists all twelve questions and the red flags.

Crawl Space Encapsulation by Area

Crawl Space Encapsulation in Wake County, NCCrawl Space Encapsulation in Johnston County, NCCrawl Space Encapsulation in Franklin County, NCCrawl Space Encapsulation in Henrico County, VACrawl Space Encapsulation in Chesterfield County, VACrawl Space Encapsulation in Jefferson County, AL

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