How to Protect Your Basement from Heavy Rain and Flooding

A basement can stay dry for years and then take on water in a single afternoon. That is usually how it goes. Not a slow drip, but a sudden flood after a summer storm drops more rain than the ground or the city sewers can handle.

Many older Canadian neighbourhoods were built long before the short, intense downpours that now hit cities like Toronto. Their lot grading, foundation drains, and sewer connections were never designed for that much water at once.

Water still follows predictable routes, though. It comes in from the surface, through the foundation, or back up through the floor drain. The team at Canada Waterproofers sees these same three entry points in nearly every wet basement they inspect, and they have been doing this work for Southern Ontario homeowners since 1998. If you block those three routes, you have dealt with most of the risk.

Start Outside, Where Most of the Water Begins

Most people start in the basement, since that is where the water shows up. But much of it comes from the roof.

A single downspout drains a big section of the roof, and in a storm all of that water lands right beside your foundation. Clean the eaves troughs at least twice a year, more often if you have mature trees nearby. Then extend each downspout so it empties at least 2 meters from the house, the distance the Intact Centre on Climate Adaptation recommends. Make sure the water runs away from your home and not toward your neighbour’s property.

Grading matters just as much. The ground should slope away from the foundation for at least 2 meters. Over the years soil settles, garden beds get built up, and walkways sink, so a yard that drained well 20 years ago may now tip water back toward the walls. A simple test is to empty a bucket of water near the foundation. If it pools there or runs toward the house, the grade needs fixing.

Window wells are the other weak spot. A well that sits flush with the lawn fills up like a bucket. It should stand 10 to 15 centimetres above the soil. A clear cover keeps out rain and leaves, as long as it does not block a window you would need as an emergency exit.

Check Your Foundation for Cracks

When the ground around a house is soaked, the water in that soil has to go somewhere. Some of it pushes against the basement walls and up under the floor, and it will find whatever gap there is.

Start with the cracks you can see. Thin hairline cracks show up in a lot of poured concrete walls as the concrete cures, and many of them never leak. Look at them the day after a heavy rain, though. Damp edges, an orange rust streak, or a white, powdery line along the crack all mean that water has been coming through. Getting it sealed through the full thickness of the wall with proper foundation crack repair is a small job next to tearing out wet drywall and carpet later. It is one of the most common fixes Canada Waterproofers carries out. The team first determines why water is entering before making any recommendations, so a single leaking crack typically receives a targeted repair instead of a full waterproofing system.

When the Weeping Tile Stops Working

The bigger problem is often one you can’t see. Weeping tile is a perforated pipe buried around the bottom of the foundation. Its job is to collect groundwater and carry it away before it builds up against the walls. Older houses often have clay tile laid in short sections, and after several decades underground, those sections can shift apart, crack, or clog with silt and roots. Once that happens, the water just sits against the footing. You’ll usually notice it as a damp strip along the bottom of the wall or water creeping in at the joint where the wall meets the floor. These are the classic signs of blocked or failed weeping tile.

There are two ways to deal with it. One is to dig down on the outside and replace the drainage as part of exterior waterproofing. The other is to work from inside the basement with a French drain, which catches water along the edge of the floor and channels it to a sump pit. Canada Waterproofers handles both interior and exterior work, and the right choice usually depends on your lot, your budget, and whether the basement is finished. Exterior work stops water before it reaches the wall, while interior work costs less and avoids digging up the yard.

Keep the Sump Pump Ready for Power Outages

If your house has a sump pump, it’s doing a lot of quiet work, and most people never check it until the basement is wet. The trouble is timing. The storms that bring the most rain are often the same ones that cut the power, and a standard pump stops the moment the electricity does.

Twice a year, in spring and fall, pour a bucket of water into the pit and watch. The float should rise and the pump should switch on within a few seconds. Then go outside and find where the discharge pipe ends. If it’s dumping water right next to the house, it’s just sending the same water back down to the pit, so aim for at least 2 meters out. A battery backup pump keeps things running during an outage.

And if the basement keeps getting wet and there’s no pump at all, it’s worth asking Canada Waterproofers whether sump pump installation would help. The team installs new pumps and battery backups and handles sump pump replacement when an older unit is close to the end of its life.

Sewer Backup: The Flood That Comes Up the Drain

Not every basement flood comes through the walls. During a heavy storm, the municipal sewer can fill faster than it drains. When that happens, sewage can flow back up the pipe and out of the lowest opening it finds, which is usually your basement floor drain. That is how most cases of sewer backup in the basement start.

A backwater valve prevents such occurrences. It sits on the main sewer line with a flap that lets water leave the house but closes when water tries to come back. Toronto and many other cities require a building permit to install one. Clean and inspect it once or twice a year, since a valve jammed with debris will not close.

In some older homes the weeping tile is also connected to the sewer. Disconnecting it and sending that water to a sump pump keeps a backed-up sewer from pushing water into the drains around your foundation. Canada Waterproofers’ two owners are both Master Plumbers, and the company handles sewer and drain repair as well as waterproofing, so this kind of job does not have to be split between two different contractors.

City Rebates That Help With the Cost

Cost puts many homeowners off, but help is available. Toronto’s Basement Flooding Protection Subsidy Program covers 80 percent of the invoice for eligible work, up to $1,600 per backwater valve, $2,250 for a sump pump, and $300 for a battery backup, with up to $6,650 per property in total. The work must be done by a licensed contractor, and you have two years after installation to apply.

Canada Waterproofers is fully licensed, insured, and WSIB-covered and has put together a guide on how to claim the $6,650 Toronto basement subsidy. Several other Ontario municipalities run their own rebate programs, so check with your city before any work begins.

Before the Next Storm

A few jobs take less than an afternoon and make a real difference:

• Clean the eaves troughs and check that every downspout empties at least 2 meters from the house
• Test the sump pump and its battery backup
• Clear the floor drain and check the backwater valve
• Rake leaves off the storm drain on your street
• Move documents, electronics, and anything valuable off the basement floor or into sealed plastic bins
• Put a water alarm near the sump pit or floor drain
• If you have noticed damp walls, a musty smell, or water at the floor joint, book a free, no-obligation assessment with Canada Waterproofers

Take a look at your home insurance while the basement is still dry. The Insurance Bureau of Canada points out that sewer backup and overland flooding are usually covered only if you have bought specific, optional coverage. Plenty of people only learn these details when they file a claim.

If water does come in, stay out of it if it is near outlets or appliances. Shut the power off at the panel only if you can reach it safely. Otherwise, call your electric utility. Once things are safe, Canada Waterproofers offers 24/7 emergency service for urgent water entry, drainage and sump pump problems, and related plumbing emergencies.

Why Homeowners Call Canada Waterproofers

Not every wet basement needs a full waterproofing system. Sometimes it is one crack, a worn out sump pump or a downspout in the wrong spot. The tricky part is knowing which one you are dealing with. That is the thinking behind how Canada Waterproofers works: find out why the water is getting in first, then recommend the repair that matches the source, so you fix the cause and not just the symptom.

The company has served homeowners since 1998 and has protected more than 15,000 homes. It is owner-operated by Carl McDowell and Slava Koval, both master plumbers, and one or both owners are personally involved in assessments and projects. Carl is also an IICRC Water Damage Restoration Technician, and HomeStars consulted him for its basement waterproofing guide. Behind them is a team of 20+ expert technicians with more than 500 years of combined field experience.

Homeowners can also expect the following:

• Free on-site assessment with no obligation
• Lifetime transferable warranty on qualifying waterproofing systems, subject to written terms and exclusions
• Fully licensed, insured, and WSIB-covered, with $5 million in liability coverage
• BBB Accredited Business with an A+ rating and a strong review record across Google, HomeStars, and TrustedPros
• 20+ industry awards, including HomeStars Best of the Best 2025 and HomeStars Best of Awards 2026
• One team for the whole job: interior and exterior waterproofing, foundation cracks, sump pumps, backwater valves, French drains, underpinning, and sewer and drain repair
• 24/7 emergency service for urgent water problems
• Price Match Guarantee on comparable work from a fully licensed, WSIB-registered, and insured contractor

Canada Waterproofers has offices in Toronto, Mississauga, and Oakville and serves homeowners across the GTA, Halton, Hamilton, Niagara Region, and other Southern Ontario communities.

Most basement floods are caused by three things: water landing too close to the house, a foundation that lets it through, or a sewer pushing back. The small habits handle a lot of it. If water keeps appearing anyway, have a contractor trace where it is coming from before you spend money on fixes. Canada Waterproofers offers free basement assessments across Southern Ontario. Call 416-333-LEAK (416-333-5325) or book online, and a specialist will tell you exactly where the water is coming from before you commit to any repair.