Basement waterproofing in Toronto starts with identifying where the water is coming from. Runoff at the foundation, groundwater entering through a failed foundation drain, and sewage backing up through a floor drain are different problems—and need different fixes. Begin with visible drainage checks, then have a licensed plumber investigate foundation drains and sewer connections when needed. Toronto also requires downspouts to be disconnected from the City sewer system, requires a building permit for backwater-valve installation, and offers capped subsidies for some eligible flood-protection work.
Find the water pathway before choosing a repair
Toronto says every home is at risk of basement flooding, including homes that have never flooded. Heavy rain and snow or ice melt can overwhelm drainage, but water may enter by several routes. Identifying the route helps prevent paying for work that does not address the cause.
- Surface runoff: Water may collect beside the house because of poor lot grading, overflowing eavestroughs, leaking or plugged downspouts, or drainage that pools near the foundation.
- Groundwater or foundation seepage: Water can enter through cracks or leaks in foundation walls, windows or doors, or through damaged or ineffective weeping tile (foundation drain).
- Sewer backup: Sewage may flow back through basement plumbing when a sewer line is blocked, broken or overwhelmed. Tree roots can enter cracked sewer lines.
- Equipment failure: A sump-pump failure can leave water collected by the foundation drainage system without a way to discharge.
Water appearing at a basement corner can be a reason to investigate the weeping-tile system, but it does not establish that the system has failed. Note where water appears, whether it follows rain or snowmelt, and whether it comes from a floor drain or plumbing fixture; share those observations with the relevant professional.
Start with exterior drainage and downspouts
Clear leaves, snow, ice and other debris from eavestroughs and downspouts. Repair leaks and sagging sections so water is carried away from the building rather than released beside the foundation. Toronto advises that disconnected downspouts should ideally discharge two metres from foundation walls.
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Toronto requires property owners to disconnect downspouts from the City sewer system. Disconnection is only useful when the runoff has a safe route: direct it away from the house without sending it onto neighbouring property or allowing it to pool on a sidewalk or driveway. A splash pad can reduce soil erosion at the discharge point. The City names a downspout extension, elbow and splash pad among the materials used for this work; its guidance also calls for capping the remaining sewer connection. See Toronto’s mandatory downspout disconnection guidance.
Check that soil slopes away from the foundation, while respecting neighbouring properties. Maintain drainage swales and, where it is safe to do so, keep debris out of catch basins. These steps address surface drainage; they do not repair a failed foundation drain or prevent sewer backup.
When to investigate foundation drains and plumbing
Weeping tile—also called drain tile—is perforated pipe around the foundation that collects groundwater and rainwater and carries it to a solid pipe or sump pit. Toronto recommends repairing or replacing damaged weeping tile. If you do not know whether the foundation drains connect to the sewer, the City recommends getting help from a licensed plumber.
For a broader internal-plumbing check, Toronto recommends having a City-licensed plumber inspect the sanitary pipe beneath the basement floor for weeping-tile connections and assess the sewer service line, backwater valve and sump pump. A plumber can help determine whether the symptoms point to foundation drainage, a sewer-service issue or a device that needs repair or maintenance.
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- Clean a backwater valve through its clean-out ports annually, as Toronto recommends.
- Inspect and maintain a sump pump according to the manufacturer’s directions.
- Consider backup power for a sump pump; severe storms can cause power loss.
Choose a device for the risk it addresses
Backwater valve
A backwater valve is intended to help prevent sewage from flowing back through the home’s plumbing during a sewer backup. It addresses a sewer-backup risk, not water entering through foundation walls or poor surface grading. Toronto requires a building permit for backwater-valve installation.
Sump pump
A sump pump removes water collected by the foundation drainage system and discharges it to an area outside. It is not a substitute for correcting poor grading or a safe discharge route, and it does not serve the same function as a backwater valve. Toronto lists sump-pump installation as permit-exempt in its guidance, but that list is not exhaustive.
Ask a qualified professional to assess compatibility with existing plumbing and the discharge arrangement, as well as capacity, alarms, backup strategy, access for service and maintenance. The City says sewage ejector pumps are not covered by its subsidy program and notes that the Ontario Building Code may not allow them in some plumbing configurations.
Check permits before work starts
Toronto’s permit guidance distinguishes among common basement projects:
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| Work | Toronto permit guidance |
|---|---|
| Basement waterproofing repairs | Listed as not requiring a building permit |
| Sump-pump installation | Listed as not requiring a building permit |
| Backwater-valve installation | Building permit required |
These categories do not settle the permit requirements for every project. If the scope includes excavation, underpinning, structural changes, a basement entrance or plumbing-system modifications, confirm requirements with Toronto Building before work begins. See the City’s building-permit guidance.
Understand Toronto’s basement-flooding subsidy
Toronto’s expanded Basement Flooding Protection Subsidy Program applies the expanded amounts to eligible work completed on or after November 12, 2025; applications for those amounts may be made starting May 1, 2026. As displayed on the City program page accessed October 8, 2026, the program offers subsidies up to $6,650 per eligible property, subject to category caps, lifetime limits and other conditions. These figures are maximum subsidies, not typical project prices or guaranteed reimbursements.
| Eligible work | Maximum subsidy shown by Toronto |
|---|---|
| One-time home plumbing assessment | Up to 80% of invoiced cost, capped at $500 |
| Backwater valve and alarm | Up to $1,600 per valve, for at most two devices |
| One sump pump and alarm | Up to $2,250 |
| Optional battery backup | Up to $300 |
| Foundation-drain severance and capping | Up to $400 |
The City lists work that may be eligible including a home plumbing assessment; up to two backwater valves and alarms; one sump pump and alarm; optional battery backup; and severance and capping of a storm sewer or external weeping-tile connection. Downspout disconnection itself is not subsidy-eligible.
Eligibility includes conditions about property type and location, downspout disconnection or an exemption, front-yard paved areas meeting zoning requirements, an application deadline, contractor and subcontractor City business licences, itemized original electronic invoices, and having no outstanding City taxes or debts. Eligible properties are single-family homes, duplexes, triplexes or fourplexes in Toronto. Verify current rules and the property’s subsidy history with the City before contracting or applying. Full terms are on the Basement Flooding Protection Subsidy Program page.
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Compare proposals by diagnosis and scope
A quote labelled “waterproofing” can describe work aimed at different failure modes. Ask the contractor to connect the proposed work to an observed water pathway and explain what evidence supports the diagnosis.
- Does the proposal address surface runoff and grading, foundation-drain collection and discharge, or sewer backup?
- Is the work exterior excavation, interior plumbing, equipment installation or a combination?
- What will be repaired, replaced or restored, and what is excluded?
- What permits and inspections apply, and who is responsible for them?
- How will the system be accessed, maintained and protected during a power outage, if applicable?
- If seeking a City subsidy, do the contractor’s business licence, itemized scope and invoices satisfy program conditions?
Compare proposals on the work included and the cause addressed, not on a general label alone. The City does not promise that a particular device or repair will eliminate all flood risk.
Know what municipal flood protection can and cannot do
Toronto’s Basement Flooding Protection Program studies and improves public sewer and drainage infrastructure. From 2006 to 2024, the City conducted Environmental Assessment studies in 67 different areas to identify causes of basement and road-surface flooding and potential municipal improvements. The program does not assess private-property drainage, and its improvements do not guarantee flood prevention; the City says they are intended to improve service levels and reduce risk where implemented.
Owners remain responsible for private lot grading, backyard and driveway drainage, foundation drains, sump pumps and backwater valves. Report flooding incidents, overflowing catch basins or sewer blockages to 311. Learn more about the Basement Flooding Protection Program.
What Toronto’s Foundation Drainage Policy means for homeowners
The City amended its Foundation Drainage Policy effective October 1, 2026. The policy is framed around specified development applications and discharge scenarios; it should not be read as a new blanket requirement for ordinary homeowner waterproofing repairs. Check the City’s Foundation Drainage Policy if a project involves development or a foundation-drainage discharge scenario covered by the policy.
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