A reinforced 12–20 mil crawl space vapor barrier costs $1,500–$4,000 installed in the Wilmington area on a crawl space of about 1,200 sq ft, or roughly $1.25–$3.33 per square foot. Size, clearance and how much old plastic has to come out move it most. Vent sealing and a dehumidifier are separate lines.
What the $1,500–$4,000 buys
That range is for the liner as a finished component, installed to the specification set out in our vapor barrier guide. A quote in this range should include all of the following, and a quote that leaves any of them unstated is not comparable with one that lists them.
- Reinforced polyethylene, 12–20 mil, meeting ASTM E1745 Class I — the scrim is what stops a puncture becoming a tear.
- Seams overlapped and taped with a tape rated for the liner, not lapped loose.
- Every pier wrapped, because the gaps around piers are where an untidy install leaks.
- The perimeter detail stated: floor-only in a vented crawl space, or run up the wall and mechanically fastened in a sealed one.
- What happens to the old material. Torn 6 mil sheet comes out as part of the job; a space full of debris or collapsed insulation is a separate cleaning line at $400–$1,500.
How the size of the crawl space changes it
The $1,500–$4,000 band is set on a 1,200 sq ft crawl space. It does not scale in a straight line with area, because getting a crew and material under the house, and finishing the perimeter and piers, cost much the same whatever the floor size. These are the base figures our cost calculator starts from for the liner line, before clearance is applied:
- 800 sq ft — about $1,200–$3,300 ($1.53–$4.08 per sq ft)
- 1,200 sq ft — $1,500–$4,000 ($1.25–$3.33 per sq ft)
- 1,600 sq ft — about $1,800–$4,700 ($1.11–$2.96 per sq ft)
- 2,000 sq ft — about $2,100–$5,500 ($1.02–$2.73 per sq ft)
Clearance moves it more than area
The calculator adds 8% where the crawl space is 2–3 feet high and 30% where it is under 2 feet, because below that height every seam, pier wrap and fastener is done lying on your back. A long, narrow footprint costs more than a square one of the same area for the same reason: the labour is at the edges.
That is why a per-square-foot figure is a check on a quote rather than a way to build one. If two quotes for the same house are far apart, compare what each says about clearance, perimeter detail and removal before comparing totals.
Liner alone, or the whole sealed system
A vapor barrier deals with the soil. On this coast the air coming in through open foundation vents is the other half of the moisture load, which is why the liner is usually priced as the first line of an encapsulation: vent sealing at $300–$1,000 and a dehumidifier at $1,200–$2,500 on top, for a full system in the $4,200–$14,000 range set out in the encapsulation cost guide.
A liner alone is the right purchase when the space stays vented and the problem is damp soil, or as the first stage of a job done in two halves. The encapsulation vs vapor barrier guide covers which one a given crawl space needs. In an AE or VE flood zone, nothing that seals the space may block its required flood openings.
Doing it yourself
Bought yourself, reinforced liner runs about $0.50–$0.90 per square foot, so the material for a 1,200 sq ft crawl space is roughly $600–$1,100 before tape and fasteners. The rest of a contractor's price is labour in a confined space, and that is where the saving comes from.
Quotes really do vary that much. A buyer on r/FirstTimeHomeBuyer in September 2026 described an estimate from a locally well-known crawl space company padded with alarming language; a reply in the same thread said a handyman had put down a vapor barrier for $1,100. The useful lesson is to get the scope in writing, not to assume the cheaper one is equivalent. The DIY guide covers where homeowner installs tend to fail.
Pricing a vapor barrier in the middle of a home purchase
If you are pricing a liner because an inspection flagged the crawl space on a house you are buying, the clock that matters is the Due Diligence Period in North Carolina's standard Offer to Purchase and Contract (Form 2-T). Until it ends, the buyer can terminate for any reason or none by written notice; after it ends, that right is gone. The due diligence fee paid to the seller is generally non-refundable outside the specific cases the contract sets out.
Repairs the seller agrees to make are recorded on a Due Diligence Request and Agreement (Form 310-T); a price reduction or closing credit belongs on a different form, Form 4-T, not on the 310-T. The NC Real Estate Commission has warned brokers about vaguely written repair requests, and "install vapor barrier" is exactly that. A written quote that states the mil, the reinforcement, the ASTM E1745 class, whether the walls are covered and how seams and piers are finished is what turns it into something both sides can hold the other to. Your agent or attorney handles the contract itself; this is not legal advice.
Read the inspection report for what it does and does not establish. North Carolina's standards require the inspector to enter the crawl space unless access is obstructed or unsafe, to say how it was inspected, and to report signs of abnormal water penetration or condensation (11 NCAC 08 .1106). They do not require a moisture-meter reading, so a report may or may not give one. Where it does, wood at 20% moisture content or more is the line the state's termite form treats as a conducive condition — more on that in the inspection cost guide.
The bottom line
Budget $1,500–$4,000 for a reinforced liner on a crawl space of about 1,200 sq ft, expect clearance and old-material removal to move it more than size, and get the specification in writing — especially if the quote is going into a repair request.
For a number against your own crawl space, use the cost estimator, or call (910) 444-2738 and we will come and measure it.