What things cost
| Work | Cost |
|---|---|
| Interior waterproofing | $80–$150 per linear foot |
| Exterior membrane waterproofing | $150–$300 per linear foot |
| Interior drainage system, whole basement | $8,000–$15,000 |
| Exterior, one wall section | $5,000–$12,000 |
| Exterior, full perimeter | $15,000–$35,000 |
| Sump pump installed | $650–$4,000 |
| Backwater valve installed | $2,000–$4,500 |
| Crack injection, per crack | $450–$1,100 |
| Window well drain, per window | $500–$1,500 |
Labour is 50 to 70 percent of the total. Toronto crew rates run about 15 percent above the national average at $75 to $120 per hour, which is most of why the same job costs more here than in a smaller Ontario city.
The Toronto subsidy, and how people lose it
The City of Toronto publishes these limits for work completed on or after 12 November 2025:
| Item | Maximum |
|---|---|
| Total per property | $6,650 |
| Backwater valve, up to two | $1,600 each |
| Sump pump | $2,250, plus $300 for a battery backup |
| Severance and capping of the storm sewer or weeping tile connection | $400 |
| Home plumbing assessment | $500 |
| Share of invoice covered | Up to 80% |
The conditions that catch people out:
- Your contractor must hold a valid City of Toronto business licence. Verify it before the work, not after.
- A backwater valve needs a building permit, and you must allow an inspection before the valve is enclosed. Once it is buried under a finished floor, that inspection cannot happen.
- For a sump pump you submit photographs of the finished installation.
- Applications go in within two years of installation.
Notice what the subsidy is aimed at: devices that stop sewer backup and pump water out. It is not a general waterproofing grant, and a contractor who implies the City will pay 80% of a $20,000 excavation is overselling it.
Outside Toronto, several Ontario municipalities run their own basement flooding programs with different names and amounts. Ask your city before you assume there is nothing.
Interior or exterior — which does my basement need?
Exterior work digs down to the footing, cleans the wall, applies a membrane and usually replaces the weeping tile. It treats the water before it reaches the concrete, and it is the more thorough fix. It also means an excavator in your garden, and it is roughly double the price per foot.
Interior work cuts a channel inside the floor slab, installs drainage to a sump and pumps the water out. It manages water that has already arrived. It is cheaper, it is done from inside in winter, and it leaves the outside of your wall wet.
Which is right depends on where the water enters, what your soil does and whether the problem is groundwater, surface water or a sewer backup. Those are three different problems and they have three different fixes, which is why any company that recommends the same solution on every driveway deserves a second opinion.
Before you spend anything: the free checks
A surprising share of wet basements are fixed outside for very little money.
- Downspouts discharging within a metre of the wall, instead of two metres out.
- Grading that slopes toward the house rather than away from it.
- Window wells with no drain, filled with leaves.
- A blocked or collapsed section of eavestrough that only shows in heavy rain.
Walk the perimeter during the next real downpour with a raincoat on. Ten minutes in the rain tells you more than an hour of sales presentation in your kitchen.
Red flags in a waterproofing quote
| What you see | Why it matters | What to do |
|---|---|---|
| Diagnosis without seeing rain | Water entry point is the whole diagnosis, and it is hardest to see on a dry day | Ask what evidence points to the entry point they identified |
| Excavation recommended before simpler fixes are ruled out | Downspouts and grading are the cheapest possible fix and are often the actual cause | Ask directly whether grading and drainage were assessed first |
| “Lifetime transferable warranty” | Only worth the company that stands behind it; many waterproofing firms are young | Ask how long the company has traded and what exactly the warranty covers |
| No City licence, in Toronto | Without it your subsidy application fails, whatever the work quality | Verify the business licence before work starts |
| Valve enclosed before inspection | Loses the subsidy permanently and hides non-compliant work | Confirm in writing that inspection happens before anything is covered |
| Deposit above 10% | Ontario’s guidance to homeowners is no more than 10% down | Stage payments against completed work |
Frequently asked questions
Sometimes the cause is outside and cheap: downspouts discharging too close to the wall, ground sloping toward the house, or a clogged window well. Check those in heavy rain before paying for excavation.
Interior drainage often does not, but a backwater valve does, and plumbing changes generally do. Confirm with your municipality, and in Toronto remember the permit is also a condition of the subsidy.
Exterior treats water before it reaches the wall and is the more thorough fix at roughly double the price. Interior manages water that has already entered and is cheaper and less disruptive. The right one depends on where the water comes from.
Installation runs $2,000 to $4,500. In Toronto the subsidy covers up to $1,600 per valve for up to two valves, a building permit is required, and an inspection must happen before the valve is enclosed.
Interior work runs $80 to $150 per linear foot and exterior $150 to $300. A full interior drainage system usually lands at $8,000 to $15,000, while excavating the full perimeter from outside runs $15,000 to $35,000.
The City’s Basement Flooding Protection Subsidy covers up to 80% of invoiced cost to a maximum of $6,650 per property, for backwater valves, sump pumps, severance and capping, and a plumbing assessment. General waterproofing is not covered.
Sources
- HomeStars, Basement waterproofing cost in Toronto, updated 21 August 2026 — homestars.com
- City of Toronto, Basement Flooding Protection Subsidy Program — toronto.ca, checked 18 September 2026
- Government of Ontario, Your rights when starting home renovations or repairs — ontario.ca, checked 18 September 2026
Prices are published ranges collected on 18 September 2026, not quotes. Subsidy amounts and conditions change — confirm with your municipality.
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