waterdamagequotesThe cause decides everything else
What is leaking? Start here
Canadians do not, mostly, have floods. They have plumbing failures and appliance failures, in ordinary weeks, plus a freeze-thaw season that most countries writing about this do not have to think about.
That is not an opinion. Search demand in Canada for flood damage runs at roughly a tenth of the demand for basement flooding, and behind both of them sit sewer backups, water heaters and washing machines. So this site starts from the cause rather than from the disaster, because the cause is what decides which part of your policy answers and what the work actually is.
The short version
- Six causes, and five of them are a plumbing or appliance failure rather than weather.
- Two of the six — sewer backup and overland water — are not in a standard Canadian policy at all.
- One number governs all of them: Health Canada puts the start of mould growth at 48 hours in an area with excessive moisture.
- What your city pays towards prevention varies by thousands of dollars across four Ontario municipalities.
Start with what is leaking
| Cause | A standard policy… | First thing to do |
|---|---|---|
| Sewer backup | does not cover it — optional endorsement | Stop using water in the house |
| Basement flooding | depends entirely which of four it is | Work out whether it is still raining |
| Water heater leak | covers the damage, not the tank | Shut the cold inlet valve |
| Appliance leaks | covers the damage, not the appliance | Pull the appliance out and look behind it |
| Roof leak | covers the ceiling, not the worn roof | Drain the bulge deliberately, into a bucket |
| Frozen pipes | covers it — unless the heat was off | Find the main shut-off before you thaw anything |
What a standard policy actually includes
Before any of the individual pages, the shape of the thing. The Insurance Bureau of Canada — the national association of Canada’s private home, car and business insurers — publishes what a standard home policy does and does not do about water. Three columns, and the middle one is where most Canadian water damage actually lives.
The same diagram as a table
| Status | Peril |
|---|---|
| In a standard policy | Sudden or accidental escape from indoor plumbing, heating or air conditioning |
| Water damage from an appliance malfunction (not the appliance itself) | |
| Interior damage from a roof leak (not the worn roof) | |
| Only if you bought it | Sewer or drain backup — optional endorsement |
| Overland water — optional endorsement | |
| Service line / water main — optional endorsement | |
| Not covered | Storm surge and tidal wave |
| Ongoing or repeated ice dams | |
| Frozen pipes, where the heat was not maintained |
Source: Insurance Bureau of Canada, Water Damage and Flood Protection and Insurance Bureau of Canada, Flooding and Insurance.
Each of those optional endorsements has its own page: the sewer backup endorsement, overland water cover and service line cover.
The one clock that governs all six
Whatever the cause, the response is organised around a single published number rather than around urgency-flavoured marketing copy.
The same diagram as a table
| When | What happens |
|---|---|
| Hour 0 | Stop the water. Photograph everything before it moves. |
| Hour 2 | Call the insurer. Ask what your policy covers. |
| Hour 12 | Extraction and air movers. Drying log starts. |
| Hour 48 | Health Canada’s mould growth window closes. |
The 48-hour figure is Health Canada’s: “Mould will begin to grow in an area with excessive moisture within 48 hours.” Source: Health Canada, Guide to addressing moisture and mould indoors.
Health Canada, Guide to addressing moisture and mould indoors · 2026
“Mould will begin to grow in an area with excessive moisture within 48 hours.” Every timeline on this site is built backwards from this number.
This is why the difference between finding a leak on day one and finding it on day five is not a difference of degree. It is the difference between a drying job and a removal job.
And the one word worth knowing
Restoration work in Canada is carried out against ANSI/IICRC S500, Standard for Professional Water Damage Restoration, fifth edition. It sorts losses by the category of the water, and that category — assigned in the first hour by a person, after an inspection — is most of what decides whether materials are dried in place or cut out.
The same diagram as a table
| Category | What it means | What it usually means for materials |
|---|---|---|
| Category 1 | From a sanitary source. Clean when it arrived. | Dry in place where the materials allow it. |
| Category 2 | Significantly contaminated. Can cause sickness. | Some porous materials come out. |
| Category 3 | Grossly contaminated. Sewage, seawater, rivers. | Porous materials are removed, not dried. |
The Category 3 wording is the standard’s own: “grossly contaminated and can contain pathogenic, toxigenic or other harmful agents and can cause significant adverse reactions to humans if contacted or consumed”. Source: ANSI/IICRC S500 (2021), Section B Definitions, quoted in the S500 Consensus Body position statement of March 16, 2026.
You are entitled to ask what category was determined and what it was based on. The standard calls that determination a “process performed by the restorer to establish the category of water for the purpose of establishing a scope of work”, which is to say it is somebody’s judgement rather than a property of the water.
What your city will pay towards prevention
The genuinely local part of this subject is not price. It is the cheque a municipality will write towards a backwater valve, a sump pump or a disconnected downspout — and those amounts differ by thousands of dollars between cities inside an hour’s drive of each other.
The same diagram as a table
| City | Maximum | Programme |
|---|---|---|
| Mississauga | $7,500 | Basement Flooding Prevention Rebate |
| Toronto | $6,650 | Basement Flooding Protection Subsidy Program |
| Ottawa | $3,000 | Residential Protective Plumbing Program |
| Hamilton | $2,000 | Protective Plumbing Program |
Line items, conditions and permit requirements for each: Toronto, Mississauga, Ottawa and Hamilton.
Questions people actually ask
What causes most water damage in Canadian homes?
Plumbing and appliance failures rather than weather. Canadian search demand for basement flooding, sewer backups and water heater leaks runs far ahead of demand for flood damage, and the perils a standard policy handles best are the indoor ones.
Which water perils are not in a standard Canadian policy?
Sewer backup and overland water are both optional endorsements. Service line cover is usually optional too. Storm surge, ongoing ice dams and frozen pipes where the heat was not maintained are excluded rather than optional.
How long do I have before water damage becomes mould?
Health Canada states that mould will begin to grow in an area with excessive moisture within 48 hours.
What does the category of the water mean?
ANSI/IICRC S500 sorts losses by how contaminated the water is. Category 1 is clean from a sanitary source, Category 2 is significantly contaminated, and Category 3 is grossly contaminated — sewage, seawater, rivers. The category decides whether porous materials are dried or removed, and it is a determination somebody makes after an inspection rather than a fixed property of the water.
Does my city help pay to prevent this?
Four Ontario cities do, at very different levels: Mississauga to $7,500, Toronto to $6,650, Ottawa to $3,000 and Hamilton to $2,000. Each has its own eligibility rules and each requires a building permit for a backwater valve.
Sources cited on this page
- Insurance Bureau of Canada, Water Damage and Flood Protection
- Insurance Bureau of Canada, Flooding and Insurance
- IICRC, S500 standard page
- ANSI/IICRC S500 (2021), Section B Definitions, quoted in the S500 Consensus Body position statement of March 16, 2026
- Health Canada, Guide to addressing moisture and mould indoors
- City of Toronto, Basement Flooding Protection Subsidy Program
- City of Mississauga, Basement Flooding Prevention Rebate
- City of Ottawa, Residential Protective Plumbing Program
- City of Hamilton, Protective Plumbing Program
Every figure above was read from the source it is attributed to on September 20, 2026. How we check this.
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