How much does crawl space encapsulation cost?
Crawl space encapsulation costs $1,500 to $15,000, with most homeowners paying around $5,500 for a complete project. Basic jobs run $3 to $7 per square foot, according to This Old House. Jobs that also need drainage, a sump pump, mold treatment or wood repair cost more.
What is crawl space encapsulation?
Encapsulation seals a crawl space off from outside air and ground moisture. A contractor covers the floor and usually the walls with a thick plastic vapor barrier, seals the seams, closes or seals the foundation vents, and in most cases installs a dehumidifier to keep the air dry. If water gets in, a drain and sump pump may be added.
What is included in the price?
Quotes usually cover some or all of these. Ask for each one to be listed separately:
- Cleaning out debris and old insulation
- Vapor barrier on the floor, and often the walls and piers
- Sealing vents, rim joists and other openings
- A crawl space dehumidifier
- Drainage and a sump pump, if there is standing water
- Mold treatment or replacing damaged wood, if needed
What makes crawl space encapsulation cost more or less?
- Size. Most pricing scales with square footage.
- Barrier thickness. Thicker barriers cost more and hold up better to foot traffic and storage.
- Water. A crawl space that floods needs drainage and a sump pump before it is sealed.
- Mold and wood damage. These have to be fixed first and are often priced separately.
- Access and height. Low, tight crawl spaces take longer to work in.
- Dehumidifier. A dedicated crawl space unit is a large part of many quotes.
How much does each part cost?
| Item | Typical cost | Source |
|---|---|---|
| Vapor barrier material only | $0.05–$0.20 per sq ft (4 mil) to $0.40–$0.60 per sq ft (20 mil) | This Old House |
| Full encapsulation | $3–$7 per sq ft; up to $10 per sq ft with extensive moisture problems | This Old House |
| Crawl space dehumidifier, installed | $800–$2,000, including wiring | This Old House |
| Sump pump, installed | $600–$2,500 | Fixr.com |
| Mold removal | $500–$4,000 | This Old House |
Is a vapor barrier the same as encapsulation?
No. A vapor barrier on the floor is one part of encapsulation. Full encapsulation also covers the walls, seals the vents and openings, and controls humidity. A floor barrier alone costs less but leaves outside air and humidity coming in through the vents.
When is encapsulation worth it, and when is a cheaper fix enough?
Encapsulation is aimed at damp crawl spaces: musty smells, condensation, mold on joists, sagging insulation, or high humidity. If the real cause is outside water from gutters, downspouts or ground sloping toward the house, fixing that first can be much cheaper and may be enough. Ask any contractor what is causing the moisture before you buy a full system.
What are the red flags in a crawl space sales pitch?
- A "today only" price or pressure to sign at the first visit
- Mold scare tactics with no moisture readings or photos of the actual problem
- A quote that is one total number with nothing itemized
- A warranty that is spoken but not written down
Common questions
How much does crawl space encapsulation cost per square foot?
Basic jobs cost $3 to $7 per square foot, and up to $10 per square foot for crawl spaces with extensive moisture problems, according to This Old House. Drainage, a sump pump or mold work adds to that.
How long does crawl space encapsulation last?
About 15 to 20 years for a quality job, according to Bob Vila (page last updated July 2022). Barrier life depends on its thickness and on whether people crawl or store things on it. Dehumidifiers need regular filter changes and eventually replacement.
Does crawl space encapsulation need a dehumidifier?
Most encapsulation systems include one, because once the space is sealed, moisture has to be removed some other way. Ask what model is included, what it costs to run, and who services it.
Can I encapsulate a crawl space myself?
Homeowners can buy vapor barrier and seal tape and do part of the work. Drainage, sump pumps, mold treatment and wood repair are usually jobs for a contractor.
Sources
- This Old House, Crawl Space Encapsulation Cost (page updated Mar 13, 2026) — thisoldhouse.com, checked Nov 3, 2026
- Fixr.com, Basement Waterproofing Cost, sump pump line (page updated Feb 6, 2026) — fixr.com, checked Nov 3, 2026
- Bob Vila, Crawl Space Encapsulation Cost, lifespan answer (page updated Jul 20, 2022) — bobvila.com, checked Nov 3, 2026
8 questions to ask any basement or foundation contractor
Ask these before you sign, whoever you hire.