What Causes Basement Flooding — And How to Stop It for Good

Basement flooding is one of the most stressful things a homeowner can deal with. Whether it’s a trickle of water near the wall or several inches of dirty water covering your floor, the damage can be expensive, messy, and emotionally exhausting.

But here’s the thing: most basement floods aren’t caused by freak accidents — they’re caused by avoidable problems that build up over time. And the good news? You can usually prevent them.

Let’s take a closer look at what causes basement flooding in Toronto and the GTA, and how UPR helps stop it — for good.

 1. Cracks in Your Foundation Walls

Water always follows the path of least resistance. Over time, concrete foundations can develop cracks due to settling, soil pressure, or freeze-thaw cycles. These cracks become open invitations for groundwater to seep into your basement, especially during heavy rain or spring thaw.

How to fix it:
Interior or exterior foundation crack repair using polyurethane injection or waterproof membranes can seal the gap and block moisture.

 2. No Sump Pump (Or One That’s Not Working)

A sump pump is your basement’s best defense against rising groundwater. When water builds up around your foundation, it flows into a pit (the sump), where a pump actively pushes it away from your home.

If you don’t have a sump pump — or your system fails during a storm — water has nowhere to go but in.

How to fix it:
Install a reliable sump pump with a battery backup, so it keeps running even during power outages (when you’re most likely to need it).

 3. Poor or Missing Waterproofing

Many older homes across Toronto, Etobicoke, and Scarborough were built without proper foundation waterproofing. Even newer homes can suffer if membranes or weeping tile systems break down or were installed incorrectly.

How to fix it:
UPR offers both exterior waterproofing (a complete barrier outside your home) and interior systems (drainage inside the basement tied to a sump pump). Both redirect water and keep your basement dry.

 4. Blocked or Broken Drains

If your home’s floor drains or sewer lines are blocked, water from inside your home has no way to escape. It can back up through the lowest drain point — usually your basement floor.

Tree roots, collapsed clay pipes, or grease buildup are all common causes in the GTA.

How to fix it:
A camera inspection will reveal the issue. From there, we may recommend drain snaking, hydro jetting, or trenchless drain replacement.

 5. No Backwater Valve

When city sewers get overwhelmed (often during major storms), wastewater can reverse direction and flow back into your home. The result? Sewage in your basement.

A backwater valve acts as a one-way gate that prevents that from happening — and in most Toronto homes, it’s now required.

How to fix it:
We install backwater valves to code and help you apply for available City of Toronto rebates (up to $1,250).

 You Don’t Have to Live With the Risk

At UPR, we’ve been protecting homes across the GTA from flooding for over 20 years. We offer real solutions — not band-aids — with honest pricing, clean work, and lasting results.

Whether your basement is already wet or you just want peace of mind before the next storm, we’re here to help.

Call 647-833-6743
Book a Free Basement Flood Inspection
Serving Toronto, North York, Mississauga, Etobicoke & beyond