Walls and ceilings
Mold removal cost
Forty square feet of mold on a finished basement wall is about $1,540 to remediate — the area sealed off, the moldy drywall cut out and bagged, the framing cleaned, and new drywall put back. Under 10 sq ft it is a cleaning job you can do for $79 of supplies; past 100 sq ft it takes a sealed work room, and 150 sq ft is $5,350. The price steps with the containment, follows the place — bathroom, basement, crawl space, attic, inside a wall — and is worth nothing if the water that grew it is still there. This prices the removal, the containment, the rebuild, the testing and the fix.
Written and edited by Pablo Ruiz Quintero
Last reviewed 2026-09-24 · Nothing you type leaves your browser
Mold removal cost calculator
How much, where, and what made it grow
Under 10 sq ft it is cleaning; over it, remediation with containment. And the moisture that grew it is what decides whether it comes back.
10 to 100: limited containment.
Damp foundation walls, finished walls with the drywall touching the concrete, stored boxes. Humidity and seepage.
Drywall, insulation, carpet: removed and replaced.
The source is known and gone.
For mold you cannot see.
Proof the job is done.
Over 10 sq ft: a contractor.
Used only to pick a regional labour rate. It stays in your browser.
40 sq ft of mold, basement walls or floor
$1,540
limited containment · $39 per sq ft before testing and the fix
Past 10 sq ft, the plastic goes up
$700 of the price is containment: plastic sealing the area and a HEPA negative-air machine, so the spores knocked loose stay in it. The removal itself is $600, and putting the drywall back $240.
The moisture first
Stopped already — good.
Mold needs water. A leak, a shower with no fan, a damp basement or crawl space grew it, and it will grow it again. Wet materials dried within a day or two do not usually go moldy, and a house kept between 30 and 50% humidity rarely does. Fix the water, then remove the mold — never the other way round.
The same place, six sizes
Basement walls or floor, with the choices above; watch the steps.
What the contractor charges for
- 40 sq ft, basement walls or floor
Damp foundation walls, finished walls with the drywall touching the concrete, stored boxes. Humidity and seepage.$600 - Limited containment
Poly sheeting round the area, a HEPA negative-air machine, protective gear. For 10 to about 100 sq ft.$700 - Putting the wall back
New drywall, insulation where there was some, taped, primed and painted, per square foot removed.$240
What it costs
National average. 40 sq ft of visible mold in the basement walls or floor, porous material removed and replaced. Not included: mold hidden beyond what is visible, duct cleaning, replacing flooring or cabinets, or a roof repair beyond a leak allowance.
Drywall put back after a leak is on the drywall repair page; the crawl space that keeps growing it, on the crawl space page; the fan that stops a bathroom doing it, on the bath fan page.
Worth knowing
- At 40 sq ft it is a remediation job, not a cleaning one: the area sealed in plastic with a HEPA negative-air machine so the spores knocked loose do not end up in the rest of the house — $700 of containment before a surface is touched.
- Basement walls or floor: Damp foundation walls, finished walls with the drywall touching the concrete, stored boxes. Humidity and seepage.
- Moldy drywall, insulation and carpet are removed and thrown out, not cleaned — the mold is in them, not on them. Putting the wall back is $240 of drywall, insulation, tape and paint here.
- The price assumes the water that grew it is already stopped. If it is not, the mold comes back and the job is paid for twice: the leak, the steam or the damp comes first.
On this page — 5 sections
Ten square feet is the line
The short version
- 40 sq ft on a basement wall: $1,540, with the drywall put back.
- Under 10 sq ft it is cleaning: $79 of supplies yourself.
- Over 100 sq ft, full containment: $5,350 for 150 sq ft.
- Fix the water first, or it is paid for twice.
The EPA draws the line at about 10 square feet, roughly 3 feet by 3. Below it, mold is a cleaning job: detergent and water on hard surfaces, anything porous cut out and thrown away, a respirator, gloves and goggles. Above it, it becomes remediation, and the price changes shape. The area is sealed in plastic and a HEPA negative-air machine pulls air out of it so the spores the work knocks loose stay inside; past about 100 square feet the seal becomes a work room with its own entry. That containment is a step in the price, not a rate — which is why 100 square feet costs 2,800 and 150 costs 4,950.
$800
8 sq ft, a contractor
The minimum
$1,960
60 sq ft
Limited containment
$2,800
100 sq ft
Still limited
$4,950
150 sq ft
Full containment
U.S. Environmental Protection Agency, A Brief Guide to Mold, Moisture and Your Home; Mold Remediation in Schools and Commercial Buildings · checked 2026-09-24
Where it is, and what it is on
The rate follows the place. A bathroom ceiling is small and fiddly; a crawl space is large and cramped; attic sheathing is large and is blasted or scrubbed and sealed, cheaper per foot; inside a wall means the drywall and insulation are opened up, bagged and put back. And the material: mold grows into drywall, insulation, carpet and ceiling tile, so they are removed and replaced, while tile, concrete and sealed wood are cleaned.
| Where | Per sq ft | 40 sq ft | 150 sq ft |
|---|---|---|---|
| Bathroom or kitchen | $18 | $1,660 | $5,400 |
| Basement walls or floor | $15 | $1,540 | $4,950 |
| Crawl space | $12 | $1,180 | $3,600 |
| Attic sheathing and rafters | $6 | $940 | $2,700 |
| Inside a wall or ceiling | $25 | $1,940 | $6,450 |
Porous material replaced where it applies; moisture already fixed; no testing. On hard surfaces the 40 sq ft basement job is $1,300.
Institute of Inspection, Cleaning and Restoration Certification, ANSI/IICRC S520, Standard for Professional Mold Remediation · checked 2026-09-24
The water first
Mold is a symptom. A slow leak in a wall, a bathroom whose fan does not vent outside, a basement or crawl space over damp ground: remove the mold without fixing the water and the same job is paid for again next year. The fix is part of the price here — a leak repaired, a fan ducted outdoors, a dehumidifier holding a basement or crawl space under 50% humidity — because without it the rest is temporary.
| Source fixed | Source left | |
|---|---|---|
| 30 sq ft in a bathroom | $1,920 with a fan vented outside | $1,420 now, and again |
| 60 sq ft inside a wall | $2,960 with the leak repaired | Grows back behind the new drywall |
| 400 sq ft crawl space | $8,800 with a dehumidifier | Next humid summer |
Testing, and who does it
Visible mold does not need a test to decide what to do: it is removed whatever it is. A test before (about $400) earns its place when there is a smell and nothing to see — behind a wall, in the ducts. A clearance test after a large job, before the plastic comes down, is how you know it is finished, and it should be done by an independent assessor rather than the company that did the work.
Before the work
- The visible area measured, patch by patch.
- What it is on: porous out, hard surfaces cleaned.
- The water found and fixed first.
- Containment described on the quote for anything over 10 sq ft.
- The rebuild — drywall, insulation, paint — on the same quote or a separate one.
- For a large job, an independent clearance test.
- Insurance checked if a sudden leak caused it.
What goes wrong
01Removing the mold, not the water
It grows back, and the job is paid for twice.
Instead — The leak, the fan or the damp first.
02Bleaching drywall
The surface whitens and the mold inside the paper keeps growing.
Instead — Porous material cut out and replaced.
03Scrubbing a large area without containment
It spreads spores through the house.
Instead — Plastic and negative air past 10 sq ft.
04Paying for tests to decide on visible mold
Visible mold is removed whatever its species.
Instead — Test only to find hidden mold, or to clear a large job.
05The remediator clears their own work
The company that did the job has every reason to pass it.
Instead — An independent assessor for the clearance test.
06Painting over it
Mold grows under the paint and shows through.
Instead — Removed, dried, then painted.
- 01Measure the visible moldLength times width of each patch, added up. Under 10 sq ft is a cleaning job; 10 to 100 limited containment; over 100 full.
- 02Note what it is onDrywall, insulation and carpet come out; tile, concrete and sealed wood are cleaned.
- 03Find the waterA leak, a bathroom without a working fan, a damp basement or crawl space. The water is fixed first.
- 04Decide on testingBefore, only to look for mold you cannot see; after, on a large job, to prove it is done.
- 05Get a remediator who does not also testThe assessor who clears the job should not be the company that did it.
- 06Plan the rebuildThe drywall, insulation and paint that went out have to come back in.
Remediation ends with holes where the moldy drywall was. The drywall repair page prices the patches by size.
Putting the wall back- Mold remediation
- Removing mold and the materials it has grown into under containment, and correcting the moisture that caused it. More than cleaning.
- Containment
- Plastic sheeting sealing the work area so spores disturbed by the work do not spread through the house.
- Negative air
- A fan with a HEPA filter pulling air out of the contained area, so air leaks in rather than out.
- HEPA vacuum
- A vacuum with a filter that catches particles as small as mold spores. Used on every surface after removal.
- Porous material
- Drywall, ceiling tile, insulation, carpet: mold grows into them, so they are removed rather than cleaned.
- Clearance test
- An independent assessor's inspection and samples after remediation, before the containment comes down.
- Black mold
- A common name for Stachybotrys and other dark molds. Removed the same way as any other mold; its colour does not change the job.
- Relative humidity
- How much moisture the air holds compared with the most it could. Kept at 30 to 50% indoors, mold rarely grows.
- Encapsulant
- A coating sprayed on cleaned wood — in an attic or crawl space — to seal stains and resist regrowth. Not a substitute for removal.
- Dehumidifier
- A machine that pulls moisture from the air. A whole-space unit in a basement or crawl space keeps it under 50%.
Common questions
- How much does mold removal cost?
- About $1,540 for 40 sq ft on a finished basement wall — $700 of containment, $600 of removal and $240 to put the drywall back. A small patch under 10 sq ft is a contractor's minimum, about $800, or $79 of supplies to clean it yourself. 150 sq ft with a clearance test is $5,350.
- How much is mold remediation per square foot?
- About $15 a square foot in a basement, $18 in a bathroom, $12 in a crawl space, $6 on attic sheathing and $25 inside a wall — before containment, which is a step, not a rate: about $700 from 10 sq ft and $1,800 past 100. All in, the 40 sq ft basement job works out at $38.5 a square foot.
- Can I remove mold myself?
- Under about 10 sq ft — 3 ft by 3 ft — the EPA says usually yes: detergent and water on hard surfaces, anything porous cut out and bagged, an N95 or better respirator, gloves and goggles, and the area dried. About $79. Larger areas, mold inside walls or ducts, or mold after sewage or flood water are for a professional with containment.
- How much does black mold removal cost?
- The same as any other mold. Black mold — Stachybotrys and the other dark species — is removed the same way, under the same containment, at the same price per square foot. The colour does not change the job; the size, the place and the material do.
- How much does mold remediation in a crawl space cost?
- About $8,800 for 400 sq ft of joists and subfloor with full containment, a clearance test and a dehumidifier — $4,800 of the removal, $1,800 of the dehumidifier. Without controlling the ground moisture it comes back; a vapour barrier or encapsulation is often part of the fix.
- How much does attic mold removal cost?
- About $5,900 for 600 sq ft of roof sheathing with a bath fan re-vented outside — the wood blasted or scrubbed and sealed at about $6 a square foot. Attic mold almost always comes from warm, moist air from below: a fan venting into the attic, or insulation blocking the soffit vents.
- Do I need a mold test?
- Not to deal with mold you can see: the EPA says visible mold is removed whatever its species. A test before (about $400) is useful when you smell it and cannot find it. A clearance test after a large job is how you know it is finished — and it should be done by an assessor who is not the company that did the work.
- Why does mold keep coming back?
- Because the water did not stop. A leak, a bathroom with no working fan, a basement or crawl space over damp ground will grow it again. Wet materials dried within 24 to 48 hours rarely mold, and a house kept at 30 to 50% humidity rarely does.
- Does insurance cover mold removal?
- Usually only when the mold follows a sudden covered event — a burst pipe, say — and is dealt with promptly, often up to a sub-limit. Mold from a slow leak, long-term humidity or flooding is usually excluded. Read the policy's mold and water sections before starting.
- How long does mold remediation take?
- One to three days for most residential jobs, longer when walls are opened and have to dry before they are rebuilt. The clearance test comes before the containment and the plastic come down.
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About the author
Pablo Ruiz Quintero — Editor
Editor of MaterialsEstimator. Decides which documents count as a source, what every default value is, and where the line sits between what the reader parses and what the engines compute.
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