What these jobs cost
A wet basement is really three separate jobs with three separate price lists, and each trade quotes its own way. Read the rate off the table, then put your own measurements above and get a band for your house.
| Job | How contractors price it | Indicative rate (2026) |
|---|
| Interior drain tile + sump | per metre of wall | $200 - $395 |
| Exterior excavation + membrane | per metre of wall | $330 - $820 |
| Crack injection | per crack | $250 - $800 |
| Exterior french drain (yard) | per metre of trench | $33 - $164 |
| Interior sealant / waterproof coating | per m² of wall face | $10 - $85 |
| Sump pump, installed | once-off | $800 - $3,000 |
| Battery backup for the pump | once-off | $600 - $1,200 |
| Crawl space encapsulation | per m² of crawl floor | $32 - $108 |
| 20 mil liner, over the 6 mil sheet | per m² covered | $3.20 - $3.80 |
| Crawl space dehumidifier, installed | once-off | $1,000 - $3,000 |
| Steel push pier | per pier | $1,500 - $3,500 |
| Helical pier | per pier | $2,000 - $4,000 |
| Concrete / pressed pier | per pier | $1,000 - $3,000 |
| Mold remediation | per m² of affected area | $110 - $270 |
Bands are indicative 2026 US contractor ranges, gathered from published cost guides - Angi, This Old House, HomeGuide and Today’s Homeowner. The crawl-space and french-drain rows come from Angi’s crawl space encapsulation guide, HomeGuide’s crawl space page (whose liner-thickness table is the source for the mil bands) and Angi’s french drain guide. They move with your city, your soil and your access, and they are not a quote. The calculator seeds its rate fields from exactly these numbers so you can overwrite them the moment you have a real estimate in hand.
How this calculator works
Every figure on this page is a real quantity times a real contractor rate. Nothing else. The four jobs differ only in what the quantity is:
Waterproofing (drain / dig) = wall run × rate per linear foot
Waterproofing (french drain)= trench run × rate per linear foot
Waterproofing (sealant) = wall run × wall height × rate per sq ft
Waterproofing (injection) = cracks × rate per crack
Crawl space encapsulation = crawl floor area × rate per sq ft
liner upgrade = (floor + walls) × delta per sq ft
Foundation repair = piers × rate per pier
piers = ceil(wall length ÷ spacing) + 1
Mold remediation = affected area × rate per sq ft
Then every one of them becomes a band:
low = quantity × your low rate
high = quantity × your high rate
typical = the midpoint of the two
The typical is the midpoint of your own band, not a fourth estimate pulled from somewhere else - so the answer is only ever as precise as the rate you gave it. A sump pump and its battery backup are once-off lines, added on top rather than smeared across the per-foot rate, because that is how they appear on a quote. The math runs in exact metric internally, so switching units changes the displayed numbers and never the answer.
Worked example
This example follows the unit system you pick in the calculator above.
A wet 30 m perimeter getting interior drain tile and a sump pump, at $200-395 per metre:
- Drain run: 30 m of wall along the inside of the footing.
- Low: 30 × $200 = $6,000. High: 30 × $395 = $11,850.
- Sump pump, installed: $800 - $3,000 as its own line.
- Band: $6,800 to $14,850, typical about $10,825 - the midpoint, not a separate guess.
- Then the settling wall: 7.5 m at 1.8 m centres = ceil(7.5 ÷ 1.8) = 5 spans → 6 piers, at $1,500-3,500 each = $9,000 - $21,000.
How many piers a foundation needs
This is the one place on the page where there is something genuinely to compute, and it is worth understanding before you read a quote.
Piers do not go in the wall, they go under it, and they carry load in the spans between them. So a run of piers needs one at each end plus one for every span in between - which is why the count is ceil(length ÷ spacing) + 1 and not simply length ÷ spacing. A 24 ft wall at 6 ft centres is four spans and five piers. Miss the end pier and you are a pier short and several thousand dollars light.
Spacing itself is not yours to choose. It is set by an engineer from your soil bearing capacity, your footing, and the load each pier carries - typically 5 to 8 ft, closer under a heavy corner. Use the count here to sanity-check a quote that seems to have too many or too few piers in it, and to understand what the contractor is charging you for. It is not a design.
Crawl space encapsulation cost
A crawl space is priced on one number: the floor area. Every published guide - Angi, HomeGuide, This Old House, HomeAdvisor - quotes crawl space encapsulation between $3 and $10 per square foot of crawl floor, and works the total up from there. A 1,000 sq ft crawl space is $3,000 to $10,000; the national range across all sizes is roughly $3,000 to $15,000.
The thing worth understanding before you read a quote is what that rate already covers. The liner does not stop at the floor - it runs up the walls and wraps the piers, and on a real encapsulation it is taped, sealed and mechanically fastened. None of that wall area is billed separately. It is inside the per-square-foot floor rate. So if a quote itemises the wall face at the full floor rate on top of the floor, you are being charged roughly twice for one liner. The calculator above deliberately refuses to do that: it takes the wall height so it knows how much surface the sheet covers, and then uses it for one thing only - the cost of specifying a heavier sheet.
That thickness is the one liner variable that genuinely moves money, and it is small:
Going from 6 mil to 20 mil is about $0.30 to $0.35 per square foot of covered surface - on a 1,000 sq ft crawl space with lined walls, a few hundred dollars against a job of several thousand. That is why the calculator charges it as a delta over the standard sheet rather than at its full price: the basic liner is already inside the rate you typed. If your contractor quoted an all-in rate that already assumes a heavy liner, leave the selector on 6 mil so you do not pay for it twice.
Two things sit outside the rate and belong on the quote as their own lines. A crawl space dehumidifier is $1,000 to $3,000 installed - about $300 to $2,000 for the unit and $700 to $1,000 in labor - and a sealed crawl space genuinely needs one, because sealing a damp space without managing the humidity just traps the damp. A crawl space sump pump is $600 to $2,500 installed, and whether you need one is a question about your water table, not your liner.
French drain installation cost
“French drain” covers two jobs with a price gap of roughly ten to one, and knowing which one you are being quoted is most of the battle.
The interior french drain is the same thing the trade calls drain tile, weeping tile or a perimeter drain, and it is expensive for a reason that has nothing to do with the pipe: the crew has to break out the concrete slab around the entire perimeter, dig the trench, lay the pipe in stone, and re-pour. You are paying for demolition and concrete work, and the drain is almost incidental. It is the first method in the calculator above.
The exterior yard drain is a shallow gravel-filled trench with a perforated pipe, run from wherever the water pools to wherever it can safely go. No slab, no footing depth, no sump - which is why it is a tenth of the price and why it is the right answer far more often than the people selling interior systems will tell you. If your problem is surface water collecting against the house after rain, this and a downspout extension may be the whole fix.
The calculator prices both per linear foot and works out the trench spoil for the exterior run, because the dirt has to go somewhere and putting the yard back is part of what you are paying for.
Mold: the size decides the method
Mold pricing looks like a simple per-square-foot rate, and it is - but the affected area also decides how the work has to be done, and that is the finding that matters more than the money:
- A small patch is a clean-up, not a remediation. Mask, gloves, goggles, a scrub and a fixed leak. No containment, no contractor.
- A mid-sized area needs limited containment - the area sheeted off in poly, HEPA vacuuming, and materials bagged before they leave the room.
- A large area needs full containment: a sealed enclosure held under negative air pressure with HEPA filtration, so spores are not pushed into the rest of the house.
Where those thresholds fall is not the same on both sides of the border, so the calculator uses the ones that apply to you - see the notes below.
And none of it is worth spending on until the water is fixed. Mold is a symptom. Remediate a wall that is still wet and it will be back inside a year.
Codes, mold limits and money where you are
In Canada, the perimeter drain at the base of the footing is called weeping tile
- that is the line item to look for on a quote. It is also what
the National Building Code of Canada, Part 9 is built around: Section 9.13 covers dampproofing and waterproofing, and Section 9.14 requires the bottom of every exterior foundation wall to be drained by drainage tile or pipe - the weeping tile - unless it can be shown to be unnecessary.
For mold, you are under Health Canada's
guidance, and the size thresholds are the part worth knowing before you call anyone: a small area is 1 m² or less; a medium area is several patches totalling under 3 m²; a single patch over 3 m² (about 32 sq ft) is a large area that needs a professional assessment - a much lower bar than the EPA's 100 sq ft.
The calculator's mold mode uses these thresholds to tell you which tier your patch falls into.
There may be public money toward this. Toronto's Basement Flooding Protection Subsidy Program pays up to $6,650 per property - up to $2,250 toward a sump pump, $300 toward a battery backup, $1,600 per backwater valve and $500 toward a plumbing assessment. Check your own municipality before you book the work; several Ontario and Prairie cities run similar programmes.
Before you spend anything
- Do the free things first. Extend the downspouts 6 ft or more from the wall, re-grade the soil so it slopes away, and clean the gutters. A meaningful share of “wet basements” are a downspout emptying against the foundation.
- Get three quotes, and make them quote the same unit. One contractor pricing per linear foot and another pricing “the job” cannot be compared. Ask for the rate and the run.
- Be suspicious of a free inspection that ends in a same-day discount. This trade has a hard-sell reputation for a reason.
- A crack that leaks and a crack that moves are different problems. Water through a stable crack is an injection job. A crack that is widening, stepping through the block, or leaving doors out of square is a foundation job - and that is the tab to switch to.
- Fix the water before the finishes. Piers, drywall, mold treatment and flooring over an unsolved leak is money spent twice.
