Crawl Space Encapsulation Cost 2026: $5,000–$15,000 Typical

Encapsulating a common crawl on a US single-family house — about 1,000 square feet of crawl floor, a reinforced liner on the ground and up the walls and piers, the foundation vents sealed, the ground cleaned enough to lay the liner, and a permit where the city requires one — often clusters around $5,000–$15,000. That is the typical crawl space encapsulation cost for that scope. Crawl space encapsulation cost per square foot, once the crawl is about that size, is typically $5–$15. A crawl space vapor barrier only, plastic on the ground with the vents left as they are, is typically $2–$4 per square foot, or $2,000–$4,000 on about 1,000 square feet. The wider national spread, about $1,500–$30,000, covers a small ground cover in a lower-cost area at the low end and a 2,000 square foot encapsulation at the high end. A foundation repair, a new sump pit on the sump pump guide, or a dehumidifier and mold remediation on a large crawl can clear that spread. These are typical planning ranges, not a survey and not a quote.

This page is the liner that closes a crawl: the ground, the walls, and the piers, with the vents sealed. A bid may call the same job a crawl space sealing or an encapsulation system. A sheet on the ground alone is the vapor-barrier row. It is not this page’s typical band. It is not a pier or a brace under a floor that has moved, which is the foundation guide. It is not the pump in the pit, which is the sump pump guide. It is not the attic, which is the attic insulation guide. It is not a coating or a drain on a basement wall, which is the basement waterproofing guide. A house with a basement and a crawl is two rooms. They are not one price.

The roll on a pallet is not the job. A 6-mil sheet can look cheap by the square foot. The bid is the crawl someone has to work in, the thickness, whether the liner goes up the walls and around the piers, the vents, the cleaning, the dehumidifier, and the permit. Price the crawl you can measure, not a per-square-foot rate from a forum. Crawl floor area is not the living area upstairs. A two-story house can have a smaller crawl than a ranch with the same bedrooms.

The rows below are ways to read one job. They are not added together. The full-encapsulation per-square-foot row is an installed square foot of crawl floor on a crawl large enough to carry the crew, about 1,000 square feet and up: a 12-mil or 20-mil liner on the ground and up the walls and piers, vents sealed, ordinary cleaning, no dehumidifier, no sump, and no wall insulation. The size rows for full encapsulation are that job at that size. The 1,000 square foot full row and the typical band are the same reading. The vapor-barrier rows are a ground cover only. The 6-mil row and the vapor-barrier per-square-foot row are the same reading. The 12-mil and 20-mil rows are the full job at that liner, not a second sheet on top of the $5–$15 row. Use an add-on row only when the bid left that line out.

Scope	Typical planning range
Full encapsulation, per sq ft	$5–$15
Vapor barrier only, per sq ft	$2–$4
6-mil ground cover, per sq ft	$2–$4
12-mil liner, per sq ft	$5–$10
20-mil liner, per sq ft	$8–$15
About 500 sq ft, vapor barrier only	$1,500–$2,500
About 500 sq ft, full encapsulation	$4,000–$9,000
About 1,000 sq ft, vapor barrier only	$2,000–$4,000
About 1,000 sq ft, full encapsulation	$5,000–$15,000
About 1,500 sq ft, vapor barrier only	$3,000–$6,000
About 1,500 sq ft, full encapsulation	$7,500–$22,500
About 2,000 sq ft, vapor barrier only	$4,000–$8,000
About 2,000 sq ft, full encapsulation	$10,000–$30,000
Dehumidifier, when the bid leaves it out	$1,200–$2,800
Sump pump, existing pit	$500–$1,500
Sump pump, new pit	$1,500–$4,500
Vent sealing, when the bid leaves it out	$400–$1,200
Insulation, crawl walls, when the bid leaves it out	$1,000–$3,000
Mold remediation, when the bid leaves it out	$1,000–$4,000
Wall and pier wrap, when the bid leaves it out	$1,500–$4,500
Permit, when the bid leaves the city fee out	$100–$500

Full encapsulation is typically $5–$15 per square foot of crawl floor once the crawl is about 1,000 square feet or larger. That rate is a typical planning rate. It includes a reinforced liner on the ground and up the walls and piers, the vents sealed, and ordinary cleaning so the liner can go down. It does not include a dehumidifier, a sump, wall insulation, or mold remediation. The low end is an open crawl in a lower-cost area and a 12-mil liner. The high end is a 20-mil liner, a tight hatch, or a crawl full of ducts. One thousand square feet is where this rate multiplies cleanly. A smaller crawl costs more per square foot than $5.

A vapor barrier only is typically $2–$4 per square foot. That is plastic on the ground. The walls and the piers stay bare, and the vents stay as they are. It is not the full-encapsulation rate with a discount. The two meet nowhere: $4 is the top of the ground cover, and $5 is the floor of the sealed system, on a crawl large enough for the rate. A ground cover and a full encapsulation are two proposals. Adding them prices two liners.

A 6-mil ground cover is typically $2–$4 per square foot. That is the vapor-barrier rate, not a second charge on top of it. Six-mil is a thin sheet. It tears where someone kneels, and it is the wrong liner to run up a wall and call a sealed crawl. One thousand square feet at $2–$4 is $2,000–$4,000, the 1,000 square foot vapor-barrier row. Use one of those rows. Do not add them.

A 12-mil liner, installed as the encapsulation — ground, walls, and piers, vents sealed — is typically $5–$10 per square foot. That is the lower and middle part of the full-encapsulation rate. It is not added to $5–$15. One thousand square feet at $5–$10 is $5,000–$10,000, inside the typical band. One thousand times $10 is $10,000. The typical top, $15,000, is a 20-mil liner on that crawl: 1,000 times $15. A 12-mil bid at $15,000 on this 1,000 square foot crawl is a different scope. Ask what the extra dollars are.

A 20-mil liner, installed the same way, is typically $8–$15 per square foot. It overlaps the 12-mil rate from $8–$10. A thick liner and a thinner one can land in the same dollars. Ask which sheet the bid names. Do not add the two rates. One thousand square feet at $8–$15 is $8,000–$15,000, inside the typical band. The $15,000 top of that band is this row: 1,000 times $15. Two thousand square feet at $8 is $16,000, which has left the typical band and sits inside the 2,000 square foot row.

About 500 square feet of vapor barrier only is typically $1,500–$2,500. Five hundred times $2 is $1,000, under the row. Five hundred times $3 is $1,500, the floor of the row and the floor of the wider spread. Five hundred times $4 is $2,000. The top, $2,500, is $5 a square foot. The crew does not get cheaper than the trip. That $1,500 is a short, open ground cover in a lower-cost area. It is not an encapsulation someone discounted. The whole row sits under the typical band.

About 500 square feet of full encapsulation is typically $4,000–$9,000. Five hundred times $5 is $2,500, under the floor, because the cleaning, the vents, and the crew do not shrink to half of a 1,000 square foot job. Five hundred times $8 is $4,000, the floor. Five hundred times $15 is $7,500. The top, $9,000, is $18 a square foot: a tight hatch, or a crawl the crew has to work through on their stomach. The row overlaps the typical band from $5,000–$9,000. The rest, $4,000–$5,000, sits under it. This is one small sealed crawl. Adding the per-square-foot row on top of it double-counts the liner.

About 1,000 square feet of vapor barrier only is typically $2,000–$4,000. One thousand times $2 is the floor. One thousand times $4 is the top. The whole row sits under the typical band. It meets a 500 square foot encapsulation at $4,000. A large ground cover and a small sealed crawl can land on that same number. Ask which one the bid is. A basement vapor barrier on the basement waterproofing guide is $500–$2,000, plastic on a basement wall or floor. The two meet at $2,000. A limited basement wall and a 1,000 square foot crawl cover are different jobs.

About 1,000 square feet of full encapsulation is typically $5,000–$15,000. That is the typical band. One thousand times $5 is the floor. One thousand times $15 is the top. This is the clean reading of the full per-square-foot row. Adding that row on top of this one double-counts the crawl. A dehumidifier, a sump, and wall insulation are not inside it.

About 1,500 square feet of vapor barrier only is typically $3,000–$6,000. One thousand five hundred times $2 is the floor. One thousand five hundred times $4 is the top. The row overlaps the typical band from $5,000–$6,000. A large ground cover and a straightforward encapsulation can land in the same dollars. They are not added. The rest of the row, $3,000–$5,000, sits under the typical band.

About 1,500 square feet of full encapsulation is typically $7,500–$22,500. One thousand five hundred times $5 is the floor. One thousand five hundred times $10 is $15,000, the top of the typical band. One thousand five hundred times $15 is $22,500, the top of the row. The row overlaps the typical band from $7,500–$15,000 and leaves it above that. It stays inside the wider spread. Do not add it to the 1,000 square foot row. A 1,500 square foot bid is one crawl.

About 2,000 square feet of vapor barrier only is typically $4,000–$8,000. Two thousand times $2 is the floor. Two thousand times $4 is the top. The row overlaps the typical band from $5,000–$8,000, and it overlaps a 500 square foot encapsulation from $4,000–$8,000. A big sheet on the ground and a small sealed system can cost the same. Ask which one the bid is. Do not price a 2,000 square foot ground cover on the $5,000 encapsulation floor.

About 2,000 square feet of full encapsulation is typically $10,000–$30,000. Two thousand times $5 is the floor. Two thousand times $7.50 is $15,000, so a mid-rate crawl of this size is where the job leaves the typical band. Two thousand times $15 is $30,000, the top of the row and the top of the wider spread. The row meets the typical band only from $10,000–$15,000. Most of it sits above $15,000. A dehumidifier, a new sump pit, or mold remediation on top of this row can clear $30,000.

Crawl space dehumidifier installation cost, when the bid leaves the unit out, is typically $1,200–$2,800. That is a crawl unit hung out of the standing water, set to drain, unit included. The floor is a straightforward unit in a crawl the crew can move through, drained to a sump or to daylight that is already there. The top is a larger unit, a condensate pump, or a drain the crawl did not have. The size rows do not include it. A portable the owner sets on the plastic can sit under $1,200. That purchase is not this row. A basement unit on the basement waterproofing guide is $800–$2,200. The two overlap from $1,200–$2,200. One dehumidifier is one invoice. A crawl that is hard to hang the unit in sits toward $2,800. A new circuit, if the bid left it out, is electrical work. It is not inside this row.

A sump pump in an existing pit, when the bid leaves it out, is typically $500–$1,500. A new pit, with a pump, is typically $1,500–$4,500. Those are the same rows as the sump pump guide. The two meet at $1,500. An expensive replacement and a straightforward new pit can land on the same number. Ask which one the bid is. Do not add the replacement on top of the new pit. That double-counts the pump. The encapsulation rows do not include either one. $5,000 plus a new pit at $1,500 is $6,500, inside the typical band. $15,000 plus a new pit at $4,500 is $19,500, which leaves the typical band and stays inside the wider spread. $30,000 plus $4,500 is $34,500, which clears the spread. A crawl with no standing water does not need the row.

Vent sealing, when the bid leaves it out, is typically $400–$1,200. It is the foundation vents closed from inside, and covered so they stay closed. The full-encapsulation rows already include it. Adding this line on top of them double-counts the vents. Add it on a vapor-barrier bid that left the vents open, or on a visit that is only the vents. The floor is a few vents foamed and covered. The top is more vents, or a brick vent finished on the outside. A single easy vent can sit under $400, because the trip does not shrink to one opening. The vapor-barrier rows do not include vent sealing.

Insulation on the crawl walls, when the bid leaves it out, is typically $1,000–$3,000. That is rigid foam or a similar board on the walls of a common crawl, after the liner is up. The floor is a short wall in an open crawl. The top is a taller wall or a longer perimeter. The full-encapsulation rows do not include it. Insulating between the floor joists, the usual choice when the crawl stays vented, is typically $2–$4 per square foot of floor. One thousand square feet at that rate is $2,000–$4,000. It overlaps the wall row from $2,000–$3,000. They are alternatives. A sealed crawl is insulated at the walls. A vented crawl is insulated at the floor. Adding both prices two assemblies. Neither rate is the attic insulation guide. That page’s typical band is $1,800–$4,000 for the attic floor. Spray foam on the crawl walls is a different product. Price it on the spray foam insulation guide. It is not this rigid-board row. A cold attic and a cold crawl are different surfaces.

Mold remediation, when the bid leaves it out, is typically $1,000–$4,000. Ordinary sweeping so the liner can lie flat is inside the encapsulation rows. This row is visible growth the liner should not cover: a limited area cleaned before the plastic goes down. The floor is a small patch the crew can reach. The top is a larger area still handled on the crawl visit. A clearance test, or a project that has left the crawl and moved through the house, can leave $4,000. This page does not price that test. $30,000 plus $4,000 is $34,000, which clears the wider spread. Do not lay a new liner over growth and call the cleaning included.

Wall and pier wrap, when a ground-cover bid left the walls and piers bare, is typically $1,500–$4,500 on about a 1,000 square foot crawl. The floor is a short wall and a few piers. The top is a taller crawl and more piers. A 2,000 square foot crawl’s walls can leave $4,500. The full-encapsulation rows already wrap the walls and the piers. Adding this line on top of them double-counts the liner. $2,000 of ground cover plus $1,500 of wrap plus vent sealing at $400 is $3,900, still under the $5,000 encapsulation floor, because the full row is one crew, a thicker liner, and sealed seams. $4,000 plus $4,500 plus $1,200 is $9,700, inside the typical band, and it is still not the $15,000 top. Three add-ons are not how to price a 20-mil system. Use the full row when the bid is the system.

A permit, when the bid leaves the city fee out, is often $100–$500. The scope rows include it when the bid says so. Add it once. A liner that does not cut a slab, open a footing, or tie to a drain the city has to approve is often the case with no fee. Do not add the row then. A new pit, or a discharge the city has to see, can sit at the top of the row. The pit itself is the sump guide.

What the range includes

The typical band assumes an existing single-family crawl of about 1,000 square feet and a full encapsulation the crew can reach through a hatch or a door. It includes a reinforced liner on the ground and up the walls and piers, the foundation vents sealed, the ground cleaned enough to lay the liner, and a permit where the city requires one and the bid includes that fee. An open crawl and a 12-mil liner in a lower-cost area sit toward $5,000. A 20-mil liner, a tight hatch, or a high-labor city sits toward $15,000. A ground cover can land under that floor and is not this scope.

A 500 square foot ground cover is the floor of the wider spread, near $1,500. A 500 square foot encapsulation can sit under the typical band and can overlap it. A 1,000 square foot ground cover sits under the typical band. A 1,500 or 2,000 square foot encapsulation leaves it once the crawl is past the mid rate. A dehumidifier, wall insulation, mold remediation, and a sump are the add-on rows.

How long the work takes depends on the square feet and what else is in the crawl, and the bid’s schedule is the one that counts. A 1,000 square foot encapsulation is often one to three days. A 500 square foot crawl can still take a day, because the setup does not shrink in half. A 2,000 square foot crawl, a mold cleaning, or a new sump pit is often several days. These are typical planning spans.

Living at home during the work is the usual plan. The crawl is the work zone. The crew needs the hatch, or an exterior door, and a place to stage the liner. The rooms above stay in use. That stay is not in the encapsulation bid.

Warranties are part of the contract, and this page is not a reading of one company’s form. An encapsulation warranty commonly covers the liner that was installed, and the term on labor is often shorter than any term on the material. Some forms are written to transfer to a buyer. Whether this one does is a sentence in the form, not a feature you can assume. The warranty does not promise a different crawl will stay dry, it does not cover a gutter that still dumps on the foundation, and it often expects the vents to stay closed and the dehumidifier, if one was sold, to be maintained. Read the form. The warranty is not a dollar line in the planning range.

Homeowners insurance and a home warranty are contracts too. A standard homeowners policy is built around sudden and accidental damage. Groundwater, a damp crawl, and a liner installed because the crawl was never dry are the kind of loss those policies commonly exclude or treat as maintenance. Flood coverage, when a policy has it, is a separate contract. A home warranty may name moisture work and still exclude a pre-existing condition, or any amount over a low dollar limit. Read the form before you treat either one as the budget. Neither one is inside the planning range.

The floor of the national spread, near $1,500, is a small ground cover. The top, toward $30,000, is 2,000 square feet of full encapsulation at $15 a square foot. A new pit at $4,500, mold remediation at $4,000, or a dehumidifier at $2,800, on top of that large crawl, can clear the top. A foundation repair that piers a settled crawl can clear it too. Treat a number above it as a different scope and ask which driver caused it.

None of the bands include new gutters, a yard trench on the French drain guide, piers on the foundation guide, a pump beyond the add-on row on the sump pump guide, blown insulation on the attic guide, or a basement system on the basement waterproofing guide. Downspouts that still dump at the foundation are the gutter job. A floor that has moved is the foundation job. Standing water is the sump job. A bare attic is the attic job. A whole-house chemical termite treatment in that damp crawl is the termite treatment guide, often $500–$2,000. Five thousand, this typical floor, is $3,000 past that termite top. A one-time ant or spider treatment is the pest control guide, often $100–$500. Five thousand is $4,500 past that pest top. Fifteen hundred, this wider floor, is $1,000 past that pest top. Do not fold a pier into the liner, do not fold the attic into the crawl, and do not fold the treatment or the insect visit into the liner price.

As a cross-check, not a bid: 1,000 square feet at $5–$15 is $5,000–$15,000. Five hundred square feet at $5 is $2,500, under the 500 square foot floor of $4,000. Two thousand square feet at $5 is $10,000, the floor of that row. If a bid and that reading are far apart, the bid is a vapor barrier only, a 20-mil liner on a large crawl, a dehumidifier, mold, a sump, or access the reading left out.

What moves the price

Driver	How it changes the bid
Full or vapor barrier	Full encapsulation is $5–$15 a square foot, and about 1,000 square feet is $5,000–$15,000. A vapor barrier only is $2–$4 a square foot, and about 1,000 square feet is $2,000–$4,000. They are not added.
Crawl size	Five hundred square feet, full, is $4,000–$9,000. One thousand is the typical band. One thousand five hundred, full, is $7,500–$22,500. Two thousand, full, is $10,000–$30,000. A short crawl does not get the $5 rate.
Liner	Six-mil is the $2–$4 vapor-barrier rate. Twelve-mil encapsulation is $5–$10. Twenty-mil is $8–$15. The 12-mil and 20-mil rows overlap from $8–$10. They are not added to the full rate.
Dehumidifier and sump	A dehumidifier left out is $1,200–$2,800. A pump in an existing pit is $500–$1,500. A new pit is $1,500–$4,500. The new-pit row includes the pump.
Vents, wrap, insulation	Vent sealing left out is $400–$1,200. Wall and pier wrap left off a ground cover is $1,500–$4,500. Crawl-wall insulation left out is $1,000–$3,000. Full encapsulation already includes the vents and the wrap.
Mold and permit	Mold remediation left out is $1,000–$4,000. A permit left out is often $100–$500. Ordinary cleaning is inside the encapsulation row.
Other work	Piers, a sump the crawl still needs, attic insulation, a French drain, and gutters are separate invoices. A liner does not lift a footing or dry an attic.
Access and region	An open crawl in a lower-cost area sits toward the floor of the row. A belly crawl, a hatch, or a high-labor city sits toward the top and can leave it.

A vented crawl leaves the foundation vents open. Outdoor air is the air under the floor. Insulation, when there is any, usually sits between the joists, and the soil is bare or covered with a loose sheet. In a humid season that outdoor air can wet the joists, the ducts, and the insulation. A sealed crawl closes those vents, runs a liner up the walls and the piers, and treats the space as part of the house. Insulation then belongs on the walls. The two are different assemblies. Adding joist-bay insulation at $2–$4 a square foot on top of a sealed, wall-insulated crawl prices both. Closing the vents without a liner, and without a plan for the water that is already in the crawl, is not the encapsulation row. It is a way to trap damp air.

In general, a sealed crawl can make the floor less cold, because the vents are no longer an opening to the weather, and it can keep humid outdoor air off the ducts. Musty air from a damp crawl can move into the rooms through gaps at the floor. Closing the vents and covering the soil can interrupt that path. This page does not price a share of a heating bill, and it does not promise a dollar of savings. It does not name a health result. A liner is not a filter, and a liner laid over visible growth is not a cleanup.

The signs of a damp crawl are ordinary. The house smells musty, especially at the hatch or after a wet week. Insulation between the joists is damp, stained, or lying on the ground. Ducts, pipes, or a furnace in the crawl sweat or show rust. Water stands, or the soil is mud. A white deposit shows on the foundation wall. Wood at the sill or a pier is darker than the rest. Mold is visible on the joists or the subfloor. A vent well holds leaves and water. One puddle under a pipe that is leaking is the pipe. It is not, by itself, an encapsulation.

Foundation repair is the pier, the shim, or the brace when the floor has moved. Encapsulation does not lift a settled footing, and a pier does not keep the soil dry. A crawl or pier-and-beam repair of one low area is typically $2,500–$9,500 on that page. It overlaps this page’s typical band from $5,000–$9,500. Ask which one the bid is. If the floor has dropped and the crawl is damp, price both. Leaving the water on a footing that was just piered is how that corner moves again. The liner is still its own line.

The pump is the sump pump guide. Standing water gets a pit and a discharge before a liner is asked to float. A replacement in a pit that is already there is $500–$1,500. A new pit is $1,500–$4,500, pump included. A battery backup on that guide is $800–$2,000 beside a primary that stays. None of those are inside the encapsulation rows. A dry crawl does not collect a pump on the way to a liner.

Attic insulation is the ceiling, typically $1,800–$4,000 to blow a common unfinished attic. A house can be cold from a bare attic and from a vented crawl in the same winter. The two projects can share a season. They do not share a bid. Encapsulation is not a reason to skip a thin attic, and a thicker attic does not dry a crawl. $5,000 plus $1,800 is $6,800 at the floors of those two bands. That is two invoices.

A French drain is the buried pipe when the yard holds water against the wall. An exterior run of about 50 to 100 feet is typically $2,000–$7,000 on that page. A liner does not move the grade, and a drain does not cover the soil. Gutters and downspouts that still empty at the foundation keep both of those jobs wet. Extending the leaders is the gutter job. A basement that takes water on the other side of the house is the basement waterproofing guide, typically $3,000–$10,000 for an interior drain and a sump on the wet walls. Do not use the basement band as the crawl price.

DIY or hire

A careful owner can roll a 6-mil ground cover across a crawl that is open, dry, and tall enough to move in, and can extend a downspout so it discharges away from the wall. The sheet has to lap, it has to stay put, and it has to reach the walls without blocking a path the water still needs. That is the vapor-barrier reading, and the labor is the owner’s. The risks are a sheet that tears, a seam that opens, and a cover laid over a problem that should have stopped the job.

Hire the encapsulation. Fastening a liner up the walls and around the piers, sealing the vents, and taping the seams are the job, and in many cities they are a permit. Hire the dehumidifier. Hanging it, draining it, and giving it power are not a weekend sheet. The circuit is electrical work. Hire any crawl with standing water, visible mold, a tight hatch, or a floor that has moved. Call 811 before anyone digs a pit. Gas, electric, and the sewer can share that ground. The pump is the sump pump guide. The piers are the foundation guide.

Hire even more clearly when the crawl holds a furnace and a duct run the crew has to wrap, when the only way in is a small hatch, or when the growth is more than a spot. Those are the jobs where the wrong liner shows up after the hatch is closed. An owner can still keep stored boxes off the plastic and keep a downspout extended. That is maintenance. It is not a sealed crawl.

Repair or replace

Is crawl space encapsulation worth it? Price the $5,000–$15,000 band when the crawl is damp, the joists or the ducts are sweating, or the house smells musty from below, and a gutter extension or a regrade cannot send the water away. Start with the downspout and the slope when those are the whole problem. A vapor barrier, $2,000–$4,000 on about 1,000 square feet, is worth it on a dry crawl with bare soil. It is the wrong purchase when the vents stay open and humid air still washes the wood. Encapsulation is not worth it as a substitute for piers on a floor that has moved, for a sump pump when water stands, for attic insulation when the attic is bare, or for a French drain the yard still needs. Price those on their own pages.

How long does crawl space encapsulation last? A reinforced liner is often planned around 20 years when the seams stay sealed, the vents stay closed, and the plastic is not a storage floor. That is a planning life, not a warranty. Replace a liner that has pulled off the walls, that has gone brittle, or that was a 6-mil sheet asked to do a sealed crawl’s job, on the size row for the square feet that still need to work. A tear at one pier, or a seam that has opened, can sit under the $1,500 floor of a new ground cover. That is a repair of that spot. A repair that means relining most of the crawl is the replacement. The dehumidifier is the shorter piece, often planned around 8 to 12 years. Replacing the unit is the $1,200–$2,800 row if the liner is sound. It is not a new encapsulation.

Keep the vents closed and the discharge of the dehumidifier clear. A sealed crawl that someone reopens to let a little air in, or a drain line that has clogged, puts the damp air back. Gutters that still dump on the wall will wet a sound liner from the outside. A sump that does not start will leave standing water under the plastic. Test the pump on the sump guide. A pier that has settled after the liner went in is the foundation guide. The liner did not lift it.

How to use this number

Ask for a written price that names the square feet of crawl floor, vapor barrier or full encapsulation, the liner thickness, whether the walls and piers are wrapped, whether the vents are sealed, and whether a dehumidifier, a sump, wall insulation, mold remediation, and a permit are included. Compare about 1,000 square feet of full encapsulation with $5,000–$15,000. Compare the full rate with $5–$15 a square foot and the vapor-barrier rate with $2–$4. Compare 500 square feet of full encapsulation with $4,000–$9,000, 1,500 with $7,500–$22,500, and 2,000 with $10,000–$30,000. Compare a 12-mil liner with $5–$10 and a 20-mil liner with $8–$15. Keep a sump pump, a foundation repair, attic insulation, basement waterproofing, and a French drain as their own lines.

A very low bid on a sealed crawl is a reason to ask whether the walls, the vents, the thickness, and the permit are included, not a reason to celebrate. A quote near $2,000 should say a ground cover, and it should say the vents are staying open. A high bid should point at square feet, a 20-mil liner, access, a dehumidifier, mold, or a sump. Two or three local bids on the same crawl, the same liner, and the same vents are the number that matters. How this site sets the band is explained on the methodology page.