Crawl space encapsulation cost dataset

What the size of the crawl space does to the figure

National figures, before any regional wage adjustment, for the default scope: full clear-out and strip-out of the old floor insulation, graded floor with an underlayment, standard 12 mil reinforced liner over floor and walls, sealed vents, insulated access door, rigid board on the foundation walls, sealed rim joist, a dehumidifier and a humidity logger.

The cost per square foot falls as the space gets bigger, and then stops falling. The model puts in a second dehumidifier above about 2,200 square feet, which is why the per-square-foot figure at 2,400 is higher than at 2,000 rather than lower. Any quote that prices a large crawl space with a single machine is either using a bigger one than we have modelled or has not thought about how far dry air travels under a floor.

The wall insulation decision

At 2,000 square feet, national wages, everything else held at the default. The walls are the thermal boundary the moment the vents close, so the first row is what a liner-and-air-sealing quote should look like — not a discount on the others.

Insulation and air barrier in one pass, and it follows a stone or irregular wall that board cannot. It is a subcontracted trade with its own rig, so it carries a mobilisation cost that board does not. That mobilisation sits on its own line rather than inside the material band, which is why the gap between board and spray here is wider than the difference in the price per square foot suggests. A quote showing the two options a couple of hundred dollars apart has not priced the rig.

How the sealed space stays dry

Same 2,000 square foot scope, changing only the humidity control. This is the widest price spread of any single choice in the dataset, and it is the one most quotes present as settled.

The cheapest of the three lands at $15,075 against $17,568 for the default, and it is not available in every house: conditioned supply air needs a duct system already running through the crawl space with capacity to give some away. The dehumidifier is the only one of the three that leaves a permanent appliance with a running cost, and that electricity is excluded from every figure on this page.

Geometry, and why the perimeter matters more than the area

Four of the dearest lines — the termination bar, the rim joist, the wall insulation and the vent seals — are priced against the perimeter and not against the floor. The calculator derives the perimeter as 4.08 times the square root of the area, which is the exact perimeter of a 1.5:1 rectangle, and lets you overwrite it. A crawl space in an L or a U runs 15 to 30 per cent longer than that for the same floor area.

• Liner bought is the covered area — floor plus wall up to just below the sill — times 1.20. The extra fifth is seam laps plus the cuts around the interior piers. At 2,000 square feet that is 2,947 sq ft of sheet to cover 2,456 sq ft.
• Insulated wall height is the wall height less 3 inches. Across much of the South a bare termite inspection strip has to stay visible, and many termite bonds are void if the wall is covered without one. It is a quantity deduction, not a line item.
• Vent count is one every 15 feet of perimeter, minimum four — at 2,000 square feet, 12. This is our estimate and carries no code label: the 1-in-150 ratio that put the vents there is expressed in square feet of net free vent area, not in a number of openings, and converting one into the other needs the net free area of the specific grille.
• Interior piers are modelled at one per 120 square feet, minimum two — here, 17. Each one has to be cut around, wrapped and taped, and piers are where liner labour actually goes.

What the liner grade is worth

The honest test is not durability in the abstract. It is whether anyone will ever crawl on the sheet or store anything on it. Both grades stop vapour equally well.

Labour hours modelled

All of this work happens lying down in a space with less headroom than a car boot, with every bag and every board passing through a hatch about two feet across. The hours per square foot are roughly double what the same work takes in a basement, and that is the honest reason encapsulation is not cheap.

• 4 labourer-hours setup, plus 0.010 per square foot to clear and rake, plus 0.017 more per square foot where decades of fibreglass have to come down and be bagged.
• +6 labourer-hours for a sump pit and +6 for a radon suction pit and riser. Somebody digs those, and it is not the electrician.
• 6 insulation-crew hours setup, plus 0.020 per square foot of covered area for the liner, half an hour per vent, 0.3 per interior pier, 0.09 per foot of rim joist and 0.035 per square foot of board on the walls.
• 20 crew-hours flat plus 0.02 per square foot of wall where spray foam is chosen, because a rig is trailered in, warmed up, masked off and hosed out whether the wall is 300 square feet or 900.
• 12 hazmat-worker hours, flat, for a localised patch of fungal growth: containment and negative air take the same time to set up in a small crawl space as in a large one.
• 4 HVAC hours per dehumidifier, or 3 for a supply register or an exhaust fan, plus 4 more for ducted combustion air and a draft test where an atmospheric appliance sits in the crawl space, or 2 for a worst-case depressurisation test where it sits elsewhere in the house.

These are person-hours: a two-man crew halves the calendar time, not the cost. The wages behind them are official BLS figures for your metropolitan area. The hours themselves are our estimate, because no public source publishes productivity figures for residential crawl-space work, and they are the assumption most worth arguing with.

Line items

The two liner grades are alternatives, never both, and so are the three wall treatments and the three humidity controls. Conditional lines appear only when the corresponding answer is yes. Two lines are deliberately lump sums that point elsewhere: the fungal growth line covers a small localised patch and the radon line quotes the fan, riser and monitor without the membrane, because the sheet is already bought in the barrier lines above.

The reasoning behind each figure

Written out so an encapsulation contractor can point at the exact assumption that is wrong. A number with no reasoning behind it cannot be corrected.

Bagging, sheeting and consumables for clearing the crawl spaceestimated, ±47%

• Contractor bags, sheeting, respirators and gloves for taking out the old vapour barrier, the fallen ductwork, the builders’ rubbish and whatever else forty years put down there. Where the old floor insulation is coming out too, it leaves in these same bags.
• Consumables only. The hours are on the labourer line, and the container that takes it off the property is its own line below, so the same dump run is not charged three times.
• Nothing on this job comes out on a machine. Everything leaves through a 24-inch hatch in buckets and bags, which is why a price per square foot down here is not comparable to a price per square foot in a basement.

Roll-off container and tipping feeestimated, ±30%

• One container, delivered, collected and tipped. A crawl space does not fill a 20-yard box even when the old insulation comes out with everything else, so this is a single line and not a per-square-foot charge.
• Tipping fees are among the most locally variable numbers on any job, and the model only adjusts hours by region, not materials or hire. This figure is therefore a flat national band and will be wrong in both directions at the extremes: check what your county charges.
• Listed separately precisely so that the bags, the hours and the dump run cannot be billed as if each of them included the other two.

Grade the soil and lay a protective underlaymentestimated, ±51%

• Rake the floor flat, take out the rocks and the construction spoil, and put down sand or a geotextile so the liner is not resting on something sharp. A liner punctured on the day it goes in fails silently for years.
• The bottom of the band is a geotextile separation layer only — the same fabric our french drain page prices at $0.11 to $0.28 a square foot, plus what it costs to carry it in and lay it out flat across a whole floor rather than into a trench. The top of the band is a sand bed spread over the whole floor.
• Importing fill to level a floor that genuinely slopes is excluded and priced separately: it is yards of material carried in through a hatch in buckets, and it is not a per-square-foot number.

Reinforced polyethylene vapour barrier, 12 milestimated, ±35%

• String-reinforced polyethylene over the floor and up the foundation walls to just below the sill. Quantity is the covered area times 1.20: the extra 20% is the seam laps plus the cuts around the interior piers, which is where crawl-space liner actually goes.
• The band separates a plain reinforced sheet at the bottom from an antimicrobial-treated one at the top. Both stop vapour equally well; the difference is what grows on the face pointing at the room.
• Manufactured goods shipped nationally, so geography barely touches this line. What moves it is how many piers the sheet has to be cut and sealed around.

Reinforced polyethylene vapour barrier, 20 milestimated, ±34%

• Roughly double the cost of the standard grade for roughly double the thickness, on the same 1.20 quantity factor.
• The honest test for whether it is worth the difference is not durability in the abstract: it is whether anyone will ever crawl on it or store anything on it. A 12 mil sheet punctures under a knee or the corner of a toolbox, and that puncture is never found.
• Same national commodity as the standard grade, priced per square foot of installed area including the overlap allowance.

Seam tape and pier-wrap sealingestimated, ±38%

• Butyl or acrylic seam tape at every lap, plus the tape that seals the liner where it wraps each interior pier.
• Priced against covered area and not against perimeter, because floor seams scale with area: a wider crawl space has more of them. Folding this into the wall termination line, as most quotes do, systematically understates it on the large crawl spaces people actually ask about.
• The band is mostly product: a general-purpose sheathing tape at the bottom, a butyl tape that still holds after ten years of soil movement at the top.

Mechanical termination bar, fasteners and wall sealantestimated, ±39%

• The liner only works as one continuous sealed surface, and the place it is most often abandoned is the top edge. This is the bar screwed into the foundation a few inches below the sill, with the fasteners and the sealant behind it.
• Priced per foot of perimeter, which is what it follows.
• The top of the band is a masonry wall that has to be drilled and plugged for every fastener, or a stone foundation where a straight bar will not follow the wall and the termination has to be made in sealant and mastic instead.

Seal the foundation ventsestimated, ±50%

• The band runs from a foam block and masonry sealant at the bottom to an insulated airtight cover with a closed-cell gasket at the top.
• The count is our estimate, not a code derivation: one vent every 15 feet of perimeter wall, minimum four. The 1-in-150 ratio that put the vents there is expressed in square feet of NET FREE VENT AREA, not in a number of openings, and converting one into the other needs the net free area of the specific grille. We are not going to publish a modelled number with a code label on it.
• Cheapest line on the page and the one that changes the character of the space. Once the vents are sealed the crawl space is unvented, and what follows from that — insulation on the walls rather than the floor above, a sealed vapour retarder, and a means of humidity control — is most of the rest of this breakdown.

Air-seal and insulate the rim joistestimated, ±48%

• Cut-and-cobble rigid board sealed with canned foam at the bottom of the band, sprayed closed-cell foam at the top. The rim joist is the single biggest air leak in most crawl spaces and the coldest surface in the assembly.
• Tied to the wall insulation choice because it is the same thermal boundary. Insulating the walls and leaving the rim joist bare puts the condensing surface exactly where the framing meets the masonry, which is the worst place available.
• Priced per foot of perimeter. Where the rim is buried behind ductwork or plumbing the work is far slower, and that is what the top of the band is for.

Rigid foam board on the foundation wallsestimated, ±42%

• Board, adhesive, mechanical fasteners and the tape at the joints. The R-value you need is a climate-zone question, and which edition of the energy code your state has adopted is published by the Department of Energy, so it is checkable before anyone quotes you.
• Quantity is perimeter times wall height less 3 inches. Across much of the South a bare, visible termite inspection strip has to be left at the top of the foundation wall, and many termite bonds are void if the wall is covered without it. If your inspector or your bond company does not require one, add those 3 inches back.
• Ask for what 16 CFR 460.17 already entitles you to: a dated, signed receipt showing the coverage area, the thickness and the R-value actually installed. Almost no encapsulation quote includes it, and it is the only part of this job you can verify on paper afterwards.
• A listed thermal or ignition barrier over exposed foam, where your inspector requires one, is NOT inside this band. It is excluded and priced separately, because pretending a cost is inside a band that cannot pay for it is exactly what this page exists not to do.

Closed-cell spray foam on the foundation wallsestimated, ±33%

• The foam itself, at roughly two inches. Closed-cell foam is the insulation and the air barrier in one pass and it follows a stone or irregular foundation that board cannot; on a flat poured wall the advantage is much smaller and board is usually better value.
• Same termite inspection strip deduction as board, and the same right to a receipt showing coverage area, thickness and R-value under 16 CFR 460.17. With sprayed foam that receipt matters more, not less: thickness is the only thing standing between the quoted R-value and what is actually on the wall, and you cannot measure it once the crew has gone.
• This band is material only. Spraying is a subcontracted trade with its own rig, and nobody mobilises one for a few hundred square feet of crawl-space wall without charging for the day. That cost is on its own line below rather than hidden in here.
• A listed thermal or ignition barrier over exposed foam is excluded here too.

Spray foam subcontractor: mobilisation, masking and application

• Twenty crew-hours flat plus a fifth of an hour per hundred square feet of wall. The flat part is the point: a spray rig is trailered in, warmed up, hosed out and masked off whether the wall is 300 square feet or 900, and every spray subcontractor has a minimum charge that reflects it.
• This is why choosing spray over board on a small crawl space costs meaningfully more than the material difference suggests, and any quote that shows the two options a couple of hundred dollars apart has not priced the mobilisation.
• Metro-adjusted wage from official BLS data for insulation workers; the hours are our estimate.

Sealed and insulated access door and frameestimated, ±47%

• Not optional in a sealed crawl space: an insulated door with a compression gasket and a latch that actually pulls it closed. A vented-crawl hatch is a louvred panel or a sheet of plywood, and either one undoes the vent sealing on its own.
• The bottom of the band is a stock insulated composite door and frame; the top is a custom size in a masonry opening, or an interior floor hatch finished to match the room.
• One per crawl space. Where there is a second entry it is usually cheaper to seal it permanently than to fit a second door. Enlarging an undersized opening is excluded: a 24-inch hatch will not pass a dehumidifier or a 4 by 8 board, and cutting masonry to widen one is priced by the opening.

Crawl-space dehumidifier, ducting and condensate lineestimated, ±36%

• A unit rated for low-temperature crawl-space operation, with a condensate pump or gravity drain and, at the top of the band, ducted supply and return so the whole space turns over rather than the corner it stands in.
• The bottom of the band deliberately does not reach the large-area consumer machines sold for basements. Those ice up at crawl-space temperatures, which is the failure mode this page should be warning about rather than pricing.
• One unit up to about 2,200 square feet. That figure is a manufacturer coverage rating, not a federal one: ENERGY STAR rates dehumidifiers in pints per day against humidity conditions, not in square feet, and we are not putting our number in a federal agency’s mouth.
• This is the largest single line in a default encapsulation and the only one with a running cost. A crawl dehumidifier draws several hundred watts whenever the compressor runs, and in a humid summer it runs a great deal. That electricity is excluded here and is a fair reason to check whether the space is wet enough to need one.

Conditioned supply register, damper and balancingestimated, ±49%

• A branch taken off the existing supply trunk into the crawl space, with a balancing damper and the boot. The cheapest of the three compliant ways to give a sealed crawl space humidity control, by a wide margin.
• It only works where a duct system already runs through the crawl space and has the capacity to give some air away. Where there is no ductwork down there, this option is not available at this price and the honest comparison is against the dehumidifier.
• The band is mostly how far the branch has to run and whether the trunk is accessible. Balancing is part of the mechanic hours below, not of this material.

Continuous-duty exhaust fan, duct and wall terminationestimated, ±46%

• A small continuous-duty fan, insulated duct and an exterior hood with a backdraft damper. Cheap to fit and cheap to run compared with a dehumidifier.
• The trade-off is where the make-up air comes from: the fan pulls it out of the house above, which slightly depressurises the house. In a house with an atmospherically vented appliance that is not a neutral choice, which is why the combustion safety test on this page applies whether or not the appliance is in the crawl space.
• The band separates a basic bathroom-grade continuous fan from an ECM unit rated for damp continuous duty, which is what belongs down here.

Temperature and humidity data loggerestimated, ±56%

• The cheapest line on this page and the only one that turns the whole job into something verifiable. A logger left down there before the work tells you whether the space is actually wet; left there afterwards, it tells you whether what you paid for worked.
• The top of the band is a unit that reports to a phone, which is the difference between finding out in a week and finding out in a year.
• Included by default rather than offered as an upsell, because a page that says “put a hygrometer down there before you spend anything” and then does not price one is not being serious.

Sump pit, basin, pump and dischargeestimated, ±45%

• A lump sum, not a design: a pit dug through the crawl floor, a lined basin, a pump, a check valve, bedding stone and a discharge line out through the wall to somewhere the water will not come straight back from.
• Needed wherever water arrives as liquid rather than as vapour. Laying a liner over standing water does not remove the water, it puts it under the plastic, where it stays; the crawl space then reads dry on a meter while the ground beneath it never is.
• Tying the pit into a new perimeter drain is NOT in this band and is not a detail: our french drain page prices an interior perimeter drain per foot, and over a crawl-space perimeter that is thousands of dollars on its own. If a quote bundles a perimeter drain into a sump line, that is the thing to question.
• Pump specification, dedicated circuit and battery backup are covered properly on our sump pump page. Here it is a lump sum because it is not the object of this job.

Sub-membrane depressurization fan, riser and monitorestimated, ±39%

• Suction pit, 3 or 4 inch solid PVC pipe, the penetration and its sealing back through the liner, an exterior riser above the roofline, an inline fan and a manometer. EPA describes the components of a radon-resistant system in these terms and describes sub-membrane depressurization as the technique for a crawl space with an earth floor.
• THE MEMBRANE IS NOT IN THIS LINE. The liner is already bought and paid for in the barrier lines on this same page, and pricing it twice is the single easiest way to make a radon number meaningless. If you have no encapsulation and only want radon dealt with, the sheet has to be added and our radon page is where that job is priced.
• EPA recommends fixing a home at 4 pCi/L or more, and recommends considering it between 2 and 4. Whether that applies to you is a test question, and the test costs almost nothing next to this line.
• Cheapest by far while the liner is being laid, because the suction pit and the pipe run go in before the sheet is sealed down. Retrofitting it later means cutting the liner open and re-sealing it. The pit-digging and riser hours are on the labourer line.

Clean and treat localised fungal growth on the joistsestimated, ±48%

• A lump sum, on purpose, and it covers a small localised patch only. EPA puts the line for a homeowner at about 10 square feet — roughly a 3 ft by 3 ft patch — and points anything larger at its remediation guide for schools and commercial buildings, which scales containment and protective equipment with the affected area.
• Containment sheeting, HEPA filtration, a borate or antimicrobial treatment, and consumables. The hours are on the hazardous materials line, at that trade’s own wage, because cleaning framing is not the job the liner crew is there to do.
• This line will NEVER be turned into a price per square foot of affected surface. That calculation belongs on our mold remediation page, and anyone with extensive visible growth needs it rather than this lump sum.
• Sealing a crawl space over wood that is growing something puts the growth inside the building envelope. If anyone in the house has health concerns about mould, that is a question for a health professional and not for a cost calculator; EPA says the same.

Ducted outdoor combustion air for an appliance inside the crawl spaceestimated, ±43%

• An atmospherically vented furnace or water heater takes its combustion air from the space it stands in and pushes its exhaust up a flue on buoyancy alone. Sealing the vents takes that air away, and the result can be a flue that spills exhaust back into a space now sealed to the house above it. CPSC’s carbon monoxide material is about exactly this class of failure.
• Two ducts, high and low, from outdoors to the appliance space, with their terminations and screens. That is what this band buys and all it buys.
• Converting the appliance to sealed combustion or moving it out of the crawl space is NOT in here. For a residential atmospheric appliance there is no conversion kit: the answer is a different appliance, and that is excluded and priced as its own job.
• This is the line almost nobody quotes, and it is the one that separates a job that improves a house from a job that creates a carbon monoxide risk. If there is a gas appliance down there, ask the contractor what happens to its combustion air before signing anything.

Carbon monoxide alarm, sealed 10-year batteryestimated, ±55%

• One alarm, on the floor where the fuel-burning appliance is. Forty dollars, on a page that spends four paragraphs arguing that sealing a crawl space can put a flue into backdraft.
• Included whenever there is any atmospherically vented appliance in the house, not only when it is in the crawl space, because sealing the crawl space changes the pressure regime of the whole building.
• A combustion appliance is not the only source of carbon monoxide in a house; CPSC’s information centre covers the rest.

Dedicated GFCI circuit and outletestimated, ±52%

• Cable, box, breaker and a protected receptacle. A dehumidifier and a sump pump together will trip a shared circuit, and a crawl space is a damp location where protection is not a preference.
• The band is mostly distance: a panel on the far side of the house is a long run through joists that somebody has to crawl the length of.
• Materials only. The electrician’s hours are on their own line, at the electrician wage.

Labourer: clear out, grade, dig and haul

• All of this work happens lying down in a space with less headroom than a car boot, moving material out through a small hatch in buckets. The hours per square foot are roughly double what the same work would take in a basement, and that is the honest reason crawl-space encapsulation is not cheap.
• 4 hours of setup, 0.010 hours per square foot to clear and rake, and 0.017 more per square foot where decades of fibreglass have to come down and be bagged. Real crews strip 2,000 square feet of saturated batts in three to five person-days, not two.
• Six hours more for a sump pit, and six for a radon suction pit and riser: somebody has to dig those and run that pipe, and it is not the electrician.
• These are person-hours. A two-man crew halves the calendar time, not the cost. The wage is official BLS data adjusted to your metropolitan area; the hours per square foot are our estimate, because no public source publishes productivity figures for residential crawl-space work.

Insulation crew: liner, piers, vents, rim joist and board

• The occupation is 47-2131, Insulation Workers, Floor, Ceiling and Wall, which is the trade that does this: cutting sheet to fit around piers, taping laps, screwing a termination bar into masonry and fitting board to the walls.
• 0.020 hours per square foot of covered area for the liner, which is about 800 square feet in a two-man day including the cutting, the taping and the wall termination. Crews that claim 1,500 are not counting the termination or the piers.
• Half an hour per vent, because sealing one properly means cleaning the masonry, fitting the block and sealing both faces, not pushing a foam plug into a hole. Around 0.3 hours per interior pier to wrap and tape it. 0.09 hours per foot of rim joist. 0.035 hours per square foot of board on the walls.
• Setup includes fitting the access door. Spray foam on the walls is not in here: it is a subcontracted trade and it has its own line.
• Metro-adjusted wage from official BLS data; the hours are our estimate.

Hazardous materials removal worker: containment and cleaning

• Twelve hours, flat, and flat is the point: containment and a negative-air machine take about the same time to set up and break down in a small crawl space as in a large one, and this line only ever covers a localised patch.
• Priced as its own trade because it is one: containment, HEPA filtration, wire-brushing the framing, applying the treatment and clearing the space. OSHA publishes what protection this work requires; it is not something the liner crew does on the way past.
• Where the growth is extensive enough to need a written remediation protocol and a clearance test, this line is too low by a wide margin and the work should be scoped by a licensed remediator instead. That is a different job, not a bigger version of this one.
• BLS wage for 47-4041, metro-adjusted; the hours are our estimate.

Plumber: set the pump, valve and discharge

• Four hours to set the basin and pump, fit the check valve, pipe the discharge through the wall and test it. The pit itself is dug on the labourer line.
• Zero unless there is standing water. Metro-adjusted wage from official BLS data; the hours are our estimate.

Electrician: dedicated circuit and equipment connections

• Three hours covers running a protected circuit from the panel and terminating a receptacle in a damp location. Two more where a radon fan needs its own supply, because the fan cannot sit inside the living space and the circuit follows it outside or into the attic.
• Metro-adjusted wage from official BLS data; the hours are our estimate.
• Zero where the humidity control is conditioned supply air and there is no sump and no radon fan, which is part of why that version of the job is so much cheaper.

HVAC mechanic: humidity control, combustion air and draft testing

• Four hours per dehumidifier to hang it, run the condensate, duct the supply and return and commission it. Three hours to take a branch off the existing trunk, fit and balance a supply register, or to fit and terminate a continuous exhaust fan.
• Four hours more where an atmospherically vented appliance sits inside the crawl space: run the dedicated combustion air, re-check the flue and carry out a draft test after the space is sealed. The test is the point of the line, because it is how you find out whether sealing the crawl space has broken the appliance’s venting.
• Two hours where the appliance is elsewhere in the house. Sealing the crawl space and bringing it inside the envelope changes the pressure regime of the whole building, so a worst-case depressurisation test is warranted even when the appliance is in a ground-floor closet.
• A different occupation and a different burden group from the construction trades, so the hourly rate is built separately rather than borrowed from the liner crew. Metro-adjusted BLS wage; the hours are our estimate.

Not included in this dataset

Vermiculite insulation and any suspected asbestos-containing material

Not estimated here at any price. Loose vermiculite in a crawl space or attic, and old pipe or duct lagging, may contain asbestos, and that is settled by testing, not by looking. Handling it is licensed, specialised work under its own rules. Putting a low number against it would be worse than putting none: get it sampled first, and price the answer separately.

Replacing a combustion appliance, or moving it out of the crawl space

Where the draft test fails and the answer is a sealed-combustion furnace or a direct-vent water heater, that is a separate job. There is no conversion kit for a residential atmospheric appliance. This page prices giving the existing appliance the air it needs, not buying a new one.

Structural repairs found once the old insulation comes down

Sagging girders, rotted band joists, failed piers and cracked foundation walls are usually discovered on the day the batts are stripped, because that is the first time anyone has seen the framing in decades. They are priced by the piece and cannot be estimated from floor area.

A listed thermal or ignition barrier over exposed foam

Where your inspector requires foam plastic left exposed in a crawl space to be covered, that coating or board is real money and it is not inside the wall insulation bands on this page. Which editions of the codes your state has adopted is published by the Department of Energy, and the inspector decides the rest.

Enlarging or creating the crawl space access

A dehumidifier and a 4 by 8 board do not pass through a 24-inch hatch. Widening a masonry opening means a lintel, cutting block and a new frame, priced by the opening and usually by a mason. Common enough to warn about, and not estimable from floor area.

Imported fill to level a sloping crawl floor

Yards of sand or soil, carried in through a hatch in buckets. The ground preparation line on this page pays for grading and an underlayment over the floor you already have, not for building a new one.

Fixing why the water is there

A liner manages vapour. It does not stop bulk water arriving. Where the cause is ground falling towards the house, downspouts discharging at the foundation or a failed footing drain, those are far cheaper to fix than anything above and have to be fixed first, or the encapsulation is sealing a wet floor.

An interior perimeter drain tied into the sump

Priced per foot on our french drain page, because it is cut through a slab or trenched around the footing and the excavation dominates it. Over a crawl-space perimeter it runs into thousands of dollars, and it should never appear folded into a sump line.

Permit fees and inspection

Some jurisdictions treat converting a vented crawl space to an unvented one as a permitted alteration, particularly where insulation and mechanical humidity control are involved, and some do not. Fees vary with no national source and are excluded rather than averaged into a figure that would be wrong everywhere.

The dehumidifier’s running cost

Several hundred watts whenever it runs, plus filters and a service life. These figures are an installation cost, not a cost of ownership, and the electricity is a real ongoing number that belongs in the decision.

Pest control, termite treatment and rodent exclusion

Frequently needed before anything is sealed, since a liner over an active infestation makes the problem harder to see and harder to reach. It is licensed work with its own pricing. Related: many termite bonds are void if the foundation wall is covered without an inspection strip, so ask your bond company before the insulation goes on, not after.

Duct sealing, duct insulation and plumbing insulation

Ductwork and pipes inside the crawl space are commonly worked on at the same time because the access is already open, and doing it then is much cheaper than going back. It is still separate scope, priced by duct run and not by floor area.

Mobilisation, travel and minimum job charges

The contractor markup in this model is meant to absorb them, and that is a modelling assumption rather than a measurement. In practice very few encapsulation firms open a file below a few thousand dollars, so the smallest liner-only scenarios on this page are arithmetically correct and may still not be buyable as a standalone job.

Warranty and transferable guarantees

Almost every encapsulation company sells a ten to twenty-five year transferable warranty, and it is either a line on the invoice or built into the price without being named. There is no national source for what it costs, so averaging one in would be inventing a number. Ask what yours costs and what voids it.

Federal tax credits

The IRS states that the Energy Efficient Home Improvement Credit can be claimed for improvements made through December 31, 2025. Work carried out after that date is not covered by it. We state the published fact and nothing else: what your own return should say is a question for a tax professional.