The short answer
HomeGuide’s national cost guide puts crawl space encapsulation at $3,000–$15,000, or $3–$10 per sq ft. This Old House gives a wider range, $1,500–$15,000, with an average of about $5,500. Neither publishes a Raleigh or North Carolina figure, and we couldn’t find one that names its source, so treat these as national yardsticks.
The number that counts is the one on a written, itemized quote. The rest of this page is a way to read it.
What each line on a quote typically costs
| Line item | Typical cost | Source |
|---|---|---|
| Crawl space inspection | $100–$250 | HomeGuide |
| Vapor barrier, installed | $1,200–$4,000 | HomeGuide |
| Vapor barrier, per square foot installed | $2–$4 per sq ft installed | HomeGuide |
| Dehumidifier, installed | $1,000–$3,000 | HomeGuide |
| Interior drain (French or perimeter) | $800–$3,000 | HomeGuide |
| Mold remediation | $1,500–$4,000 | HomeGuide |
| Crawl space repair, general | $500–$8,000 | HomeGuide |
| Permit | $100–$250 | This Old House |
| Labor, as a share of the total | 50–70% | This Old House |
Not every job has every line. A crawl space that’s dry underfoot may need only the liner, sealing and a dehumidifier. One with standing water adds drainage; one with mold adds remediation; one with soft joists adds framing repair, which is priced on the sagging floor and joist page.
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Cost by crawl space size
Per-square-foot ranges make a rough estimate easy: multiply the crawl space’s floor area by the low and high rates, then add any separate lines such as drainage or mold work.
Example: at HomeGuide’s $3 to $10 a square foot, a 1,000 sq ft crawl space works out to about $3,000 to $10,000 before extras, and a 1,600 sq ft one to about $4,800 to $16,000.
Two cautions. Per-square-foot math overstates very large, simple crawl spaces, where setup costs spread thin, and understates small, cramped ones. And the floor area of a crawl space is often less than the house’s living area, since porches, garages and additions may sit on slabs.
What pushes a Raleigh job up or down
- Water. This Old House says rates climb toward the top of its range for crawl spaces with extensive moisture problems. North Carolina’s code also wants the floor graded to low spots, with a drain to daylight or a sump pump at each low spot, so a wet site adds real work.
- Height and access. Low crawl spaces, a small access door and lots of ductwork slow every step.
- Clean-out. Old fiberglass batts, debris and an old torn plastic cover have to come out first.
- The drying method. A dehumidifier is a line item with its own drain and outlet. Supply air from the home’s system needs an H-3 heating license under North Carolina’s rules, so it brings in an HVAC contractor.
- Walls. Covering the walls with liner is allowed, but not required by North Carolina code, so a quote with full wall coverage and one without are different scopes.
- Insulation. Some plans add wall insulation; others leave the floor insulation in place.
- Framing repair. Rot or termite damage found during the job is usually priced separately.
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Why two quotes for the same crawl space differ
Scope. The biggest gap is usually what’s included. One quote may cover liner, sealing, dehumidifier, drain and permit; another may cover the liner and leave the rest as “options”.
Liner choice. The code minimum is 6-mil polyethylene or equivalent. Thicker, reinforced liners cost more and stand up better to foot traffic. Ask for the product name and thickness in writing.
Dehumidifier. Advanced Energy notes there is no standard protocol for sizing a crawl space dehumidifier; manufacturers give general guidelines. So two contractors can propose different units for the same space. Ask why that size.
Warranty and service. Some prices include a yearly monitoring visit; others charge for it separately or require it to keep the warranty valid.
Who’s doing the electrical and drainage. A dehumidifier needs a dedicated outlet in Advanced Energy’s sample design, and a sump needs power too. Check whether that work is in the price.
Costs that catch people out
- Running the dehumidifier. HomeGuide estimates $10–$30 per month in electricity.
- Upkeep. Filters, condensate pumps and humidity sensors need attention, and some warranties require a paid annual visit.
- Mold found mid-job. Remediation is a separate line, at $1,500–$4,000 in HomeGuide’s guide.
- Skipping the permit. It’s required for the conversion regardless of cost, and Raleigh warns that insurance may not cover problems caused by unpermitted work.
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How these numbers were gathered
Every figure on this page comes from a national cost guide, HomeGuide (updated January 2026) or This Old House (updated March 2026), each linked under Sources. Both are publishers, not contractors, and both describe national averages. We found no Raleigh-specific study that names its data source. Once a local contractor shares real job prices, they’ll be added and labeled as theirs.
Want a written, itemized price for your crawl space? Call to schedule a crawl space inspection.