A fall checklist to keep water out of your basement before the spring thaw

Basement water in the GTA tends to arrive at two moments: during heavy rain, and when snow and ice melt. The City of Toronto says every home is at risk, even one that has never flooded. Fall sets up both. Leaves fill the eavestroughs just as the autumn storms arrive, and anything that isn’t draining properly in November will be frozen in place by January, waiting for the first thaw.

The ground is still soft now, which makes outside fixes easier. Once it freezes, regrading and digging have to wait for spring, and spring is exactly when the meltwater shows up. Most of this list is a weekend of checking and a few small purchases. The bigger items, like a backwater valve or a new sump pump, are work for a licensed plumber, and in Toronto they may qualify for a City subsidy.

If you’re planning to finish your basement, this list matters even more. We always ask about water before we plan a basement, because water that gets in after the drywall is up costs far more to deal with than water you stop now.

Toronto recommends cleaning eavestroughs at least twice a year, and late fall, once most of the leaves are down, is the cleaning that counts. A trough packed with leaves overflows right beside the foundation, which is the last place you want the water. If the roof is high or steep, hire the job out rather than balancing on a ladder in the wind.

• Scoop out leaves and grit, then run a hose to check that the water reaches the downspout
• Check every elbow and outlet, where clogs like to hide
• Look for sagging sections and low spots where water sits and freezes
• Tighten loose brackets before snow and ice add weight
• Fix leaking joints so water doesn’t run down the wall

In Toronto it’s mandatory for property owners to have their downspouts disconnected from the City’s sewer system. A downspout that still runs into a pipe in the ground sends roof water into a sewer that can overload in a storm, which is one of the ways basements end up flooded. When we plan a basement, we check every downspout on the house for this. If yours still goes into the ground, the City’s downspout page explains how to disconnect it and cap the old pipe, and how to apply for an exemption where disconnection would be hazardous or isn’t technically feasible.

Once a downspout is disconnected, where the water goes matters. The City suggests it drain ideally two metres from the foundation walls, onto your own property rather than a neighbour’s yard, the driveway or the sidewalk. A splash pad at the end stops erosion.

Winter adds two wrinkles. Take down a rain barrel before it freezes and cracks, and put an extension back on the downspout so the water still goes somewhere sensible. And remember that water from an extension can freeze where it lands. Route it away from paths, steps and the spot where you walk to the car, so a drainage fix doesn’t turn into a sheet of ice.

Soil next to a house settles over the years, and a yard that once sloped away from the foundation can end up sloping toward it. When we walk a property, we stand back and look at the ground along each wall, and you can do the same. Toronto advises making sure the grading slopes away from the foundation, without pushing water onto a neighbouring property. Small low spots can be topped up with soil now; a bigger regrading job is best planned for spring.

Look at the side yard between your house and the next one too. Where houses share a shallow drainage swale along the property line, Toronto asks owners to keep it clear. Stacked firewood, a shed or a new garden bed in the wrong place can send water toward a foundation.

Once the snow arrives, where you pile it matters. The City suggests shovelling snow away from the foundation and onto the lawn rather than the road. If it’s safe, clearing the catch basin on the street in front of your house helps meltwater get into the storm sewer instead of pooling at the end of the driveway.

Window wells are small, so they get forgotten, and they fill with leaves quickly. Clear them out, check that the drain at the bottom, if there is one, isn’t blocked, and look at the seal where the window frame meets the foundation. Toronto lists window wells, along with walls, floors and windows, among the places to seal cracks and leaks.

A clear cover over each well keeps out leaves and most of the snow while still letting light in. If the window is a bedroom’s way out in an emergency, make sure the cover can be pushed open from inside. And if water has ever stood in a window well after a storm, tell us when we talk about finishing the basement. It often explains a stain on the wall below.

If your house has a sump pit, the pump is the last line of defence for the water your weeping tile collects. We suggest a quick test now. It’s far better than finding a problem during the first thaw.

1. Check the pit

   Lift the cover and look for debris, gravel or silt that could jam the float or clog the intake.

2. Fill it

   Slowly pour a bucket or two of water into the pit until the float rises. The pump should start on its own and shut off once the water drops.

3. Follow the water outside

   Go out and see where the discharge ends up. Toronto says it should empty onto a permeable surface, such as lawn, garden or gravel, at least two metres from the foundation wall.

4. Watch for frozen lines

   A discharge pipe that dips into a low spot or ends under a snowbank can freeze and block in winter. Keep the outlet clear and sloped so it drains.

5. Plan for power cuts

   Storms knock out power exactly when the pump is needed most. A battery backup and an alarm are worth considering, and Toronto’s subsidy covers part of both.

A backwater valve closes the sewer line when the city sewer backs up, so sewage can’t come up through your floor drain. It only works if it can move freely. Toronto recommends cleaning it every year through the clean-out ports, and maintaining and inspecting it according to the manufacturer’s directions. Fall, before the heavy storms and the spring melt, is a good time to put it on the calendar.

Know what it means when the valve is closed. While it’s shut, water from your toilets, sinks, dishwasher and washing machine has nowhere to go and will back up into the house, so the City advises not using any plumbing fixtures until it reopens. An alarm tells you when that’s happening.

If you don’t have a backwater valve yet, installing one is plumbing work that needs a building permit and an inspection, and the City says not to cover or enclose it before the inspection is done. That’s why we put it at the start of a basement renovation, never at the end.

Walk the basement with a flashlight and look closely at the foundation walls and floor. Toronto suggests sealing cracks and leaks in walls, floors, windows and the foundation as part of keeping water out. A thin, dry crack that hasn’t changed in years is different from one that’s wide, damp or getting longer. The second kind is worth having someone look at before winter, and if you’re planning a basement renovation, point it out to us at the walk-through.

A damp floor in the corners can be a sign that the weeping tile, the perforated pipe around the foundation, isn’t doing its job. In some older houses it’s also connected to the sewer, and the City recommends disconnecting it, usually with a sump pump and a backwater valve. A licensed plumber can tell you how your house is set up, and Toronto’s subsidy covers part of a one-time home plumbing assessment.

Since May 1, 2026, the City of Toronto has offered up to $6,650 per property for eligible flood-protection work completed on or after November 12, 2025. Owners of single-family homes, duplexes, triplexes and fourplexes in Toronto can apply. Each subsidy covers up to 80 per cent of the invoiced cost, to the limits below.

The money arrives after the work, and the rules are strict. We’d check these points before anything is installed.

• Your downspouts must already be disconnected, or the City must have granted an exemption. Disconnecting them isn’t subsidized.
• Every contractor and subcontractor needs a valid City of Toronto business licence at the time of the work. Check with the City’s lookup tool before work starts.
• Keep the original electronic invoices, itemized and marked paid in full.
• Apply within two years of the installation.
• Front-yard paving and parking pads must meet the zoning by-law.
• Properties have lifetime maximums, so ask the City whether yours has received a subsidy before.
• Applications are first-come, first-served and depend on annual funding, and the City says payment can take up to 10 weeks.

Treat big storms as a free inspection. A few minutes downstairs afterwards tells you more than any dry-day visit, and it gives us better information if you later plan a renovation.

• Check the corners, the bottom of the walls and around the floor drain for damp
• Look at the eavestroughs from outside: are they overflowing anywhere?
• Listen for the sump pump, and check that it stopped again
• Look for water standing in window wells or against the foundation
• Take dated photos of anything you find

Planning to finish the basement once it stays dry? Our basement page is the place to start. Outside Toronto, ask your city whether it runs a flood-protection program before you budget.