What to Do Immediately After a Basement Flood

Your basement has flooded. You just discovered it. What you do in the next 60 minutes has a direct impact on how much damage you end up with, how big your insurance claim needs to be, and whether you end up with a mold problem in three weeks.

Here is a practical, step-by-step guide based on what we see in Toronto and Oakville homes every week.

Safety Checks Before You Enter

Before you go into the basement, check two things.

First: is there any risk that electrical outlets, panels, or fixtures are below the water level? If yes, do not enter until the power is confirmed off. In most Toronto and Oakville homes, the electrical panel is in the basement. If the panel itself is submerged or the water level is near electrical outlets, call your utility company before entering. This is not a precaution — flooded basements with live electrical current have killed people.

Second: where did the water come from? If there is a smell of sewage — which is present in almost every sewer backup event — the water is Category 3 contaminated sewage. Do not walk through it without waterproof boots and do not let children or pets near it. Sewage water contains live pathogens that cause serious illness on contact with skin or through inhalation.

Stop the Water Source If You Can

If the flooding is from a burst pipe or an appliance, the priority is to stop the water source. Turn off the water main (usually near your water meter, which in Toronto and Oakville homes is typically in the basement near the front wall). If you cannot locate it quickly, call your municipality's emergency line — both the City of Toronto and the Region of Halton have 24-hour emergency lines.

If the flooding is from sewer backup through a floor drain, there is no water source to stop. The water is coming from the municipal sewer system and will stop when the sewer pressure reduces — typically within a few hours of the storm passing. Do not pour anything down the floor drain. Do not try to block it with something heavy. Call us and wait.

If the flooding is from overland flooding (water entering through a window well, door, or foundation crack at grade), the source stops when the storm stops. Move valuables off the floor to the extent you can safely do so.

What to Do in the First 60 Minutes

In order of priority:

1. Confirm it is safe to enter (electrical, sewage check)
2. Stop the water source if it is a pipe or appliance
3. Call a restoration company — right now, not tomorrow. Every hour matters for mold prevention and restoration timeline.
4. Take photos and video before moving anything — this is your insurance documentation
5. Move valuables, documents, and electronics off the floor if you can do so safely without extended contact with sewage water
6. Call your insurance company to report the event — you have a duty to report promptly under most Ontario policies

How to Document for Insurance

Your phone camera is your insurance tool for the next 30 minutes. Here is what to capture:

• Wide shots of the entire affected area showing water level
• Close-up of the floor drain or entry point if visible
• All damaged items — furniture, appliances, flooring
• Any water staining on walls showing the waterline
• Any evidence of where the water came from

You do not need to be a professional photographer. You need to document that the event happened, what was affected, and what the entry point was. If the entry point is a floor drain (sewer backup endorsement claim) versus a foundation crack above grade (overland flooding endorsement claim), capturing this correctly now determines whether your claim gets paid under the right endorsement. Learn more about why this distinction matters in our guide to sewer backup vs flood damage insurance.

What Not to Do

These are the most common mistakes Toronto and Oakville homeowners make in the first hour after a basement flood:

• Do not try to dry it yourself with a shop vac and fans. A shop vac removes water but cannot extract water from the pores of materials. Consumer fans move air but do not lower the humidity level in the space. Commercial drying requires industrial-grade dehumidifiers and high-velocity air movers. DIY drying leaves moisture in materials that causes mold within 48 hours.
• Do not throw anything away before documenting it. Everything in the flooded area is potential insurance claim evidence. Document, then dispose.
• Do not wait and see if it dries on its own. It will not. Concrete and drywall will appear to dry at the surface while remaining well above mold threshold levels inside. This is the origin of most post-flood mold problems in Toronto.
• Do not ignore a floor drain backup as a minor event. Category 3 sewage backup is a biohazard. It requires professional decontamination. What looks like dirty water receding is leaving pathogenic contamination on every surface it touched.