The short version
Home insurance in Ontario follows the water, not the mould. If the mould grew because of a sudden and accidental water loss your policy covers, such as a burst pipe or a failed washing machine hose, the clean-up is often handled as part of that water damage claim. If it grew from a slow leak, damp air or a maintenance problem, it is usually excluded.
Your own policy wording decides. Some policies also limit how much they pay for mould, even when the water loss itself is covered.
Why insurers look at the water first
The Insurance Bureau of Canada puts the principle plainly: insurance is meant to cover sudden and accidental loss, and a home insurance policy is not a maintenance contract. Most mould decisions follow from that.
Many Canadian home policies list mould, fungi and spores as an exclusion, often next to rot, dampness and condensation. A common exception is mould that results directly from a peril the policy does insure, such as the sudden escape of water from a pipe or appliance. So the adjuster starts with the water: where it came from, and whether that source is covered.
| Where the water came from | How the mould is usually treated |
|---|---|
| Sudden escape from plumbing or an appliance: a burst pipe, a split supply line, a failed water heater | Often covered as part of the water damage claim when reported promptly |
| Sewer or floor drain backup | Usually covered only with optional sewer backup coverage |
| Heavy rain or snowmelt entering at ground level | Usually covered only with optional overland water coverage |
| Water seeping through the foundation | Usually excluded; some insurers offer optional ground water coverage |
| An ice dam leaking into a ceiling | Sudden damage is often covered; ongoing or repeated leaks may be treated as maintenance |
| A slow drip under a sink or behind a shower wall | Usually excluded as continuous or repeated leakage |
| Condensation, high humidity, or a bathroom fan venting into the attic | Usually excluded as gradual damage or maintenance |
Two more details catch people out. First, some policies limit mould coverage. In its 2024 review of home insurance claims, the Financial Services Regulatory Authority of Ontario (FSRA) reported that insurers flagged mould-related problems as an area that may have limited coverage. A policy can cover the water loss and still pay for mould only up to a separate, lower limit. Second, some wordings exclude the cost of testing or assessing mould, so check with your adjuster before you pay for a lab sample.
What to do when you find mould
- Find and stop the water. Shut off the fixture, or the main if you cannot find the source, and run a dehumidifier in the room. Policies expect you to take reasonable steps to prevent further damage; in Ontario that duty is one of the statutory conditions set by the Insurance Act.
- Photograph before anything moves. Take photos and video of the mould, the water source, stains and tide lines on walls, damaged contents, and wide shots that show where each one is. Write down the date you found it.
- Leave the mould in place. Scrubbing, scraping or tearing out mouldy drywall without containment spreads spores (see black mould in the basement for the safety side), and it removes evidence the adjuster may want to see. Keep damaged items until your insurer confirms you can throw them out.
- Read the water and mould wording. Look at the water damage exclusions, any mould or fungi exclusion, any special limit for mould, and whether you carry sewer backup, overland water or ground water coverage. Your coverage summary or declarations page lists the endorsements you carry.
- Call your insurer promptly. Ontario’s statutory conditions call for written notice of a loss “forthwith”, and the Insurance Bureau of Canada tells policyholders to report as soon as possible. Delay can be held against a claim, and mould that spreads while you wait may be treated as damage you could have prevented.
- Keep records. Note the claim number, the adjuster’s name and every call. Keep receipts for emergency costs such as a plumber or a dehumidifier.
If you cannot tell how far the growth goes, a mould inspection maps it with moisture meters and thermal imaging. A lab test is rarely needed to open a claim; when mould testing is worth it covers the exceptions.
What the adjuster usually looks at
After you report the loss, an adjuster reviews the circumstances and the documents you provide. On a mould claim that usually comes down to four questions.
- Cause. Where the water came from, and whether that source is an insured peril on your policy. A failed supply line and a downspout dumping water against the foundation lead to very different answers.
- Timing. When the water started, and how long the materials stayed wet. Health Canada notes that mould can begin to grow within 48 hours of excess moisture, so some growth after a recent burst pipe is expected. Signs of a much older problem, such as rotted framing or several layers of staining, point to water over weeks or months.
- Maintenance. Whether the cause was something the owner was expected to look after: failed caulking, a corroded fitting that dripped for months, an attic with blocked soffit vents. FSRA’s review notes that wear and tear is typically excluded because upkeep is the homeowner’s responsibility.
- Mitigation. Whether you stopped the water and started drying once you knew about it.
How documentation helps
The adjuster makes the coverage decision, and they make it from evidence. The clearer the evidence on cause and timing, the less that decision rests on assumption.
- Moisture readings. Meter readings show where the water travelled and which materials are still wet. Readings taken again after drying show the source was dealt with.
- Photos. Dated photos of the source and the damage, including the materials behind the wall once they are opened.
- A written cause of loss. A plain statement of the moisture source and how it led to the growth. On a mould claim this matters most, because the cause is what decides coverage.
- A scope that separates causes. If part of the growth comes from a covered leak and part from a long-running humidity problem, a scope that splits the two lets the adjuster assess each part on its own.
How YAREX works with your adjuster
We start the way a mould inspection does: find the water first. Moisture meters and a thermal camera show how far the wet area reaches behind finished surfaces, and we photograph what we find and trace it back to a cause. You get a written finding with photos, readings, the likely moisture source and a recommended scope, in plain language you can hand to your insurer. We document the cause, because that is what decides coverage, and we write scopes your adjuster can work with. We will tell you what we found and the likely cause, but the coverage decision is the adjuster’s.
If the work goes ahead, mould remediation runs under containment and negative air, the moisture source is repaired before anything is closed up, and our own renovation crews rebuild. You can choose your own contractor, even if your insurer suggests one. Your insurer estimates the damage, and if your contractor charges more than that estimate you may be responsible for the difference, so agree the scope with your adjuster before the work starts.
See how mould removal and remediation runs, book a mould inspection, or call (343) 947-2298 anywhere in Etobicoke, Toronto and the GTA. If the mould followed a leak or a flood, read how water damage insurance claims work too.
Published November 3, 2026.
The service behind this guide
YAREX Renovation & Restoration, a licensed and insured Etobicoke contractor, removes and remediates mould (mold) in homes and condos across Toronto and the GTA.
Mould Removal & Remediation in Toronto & Etobicoke
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