What is Interior Basement Waterproofing?

Interior waterproofing is a smart choice for basements in the GTA including Toronto, Mississauga, Brampton, Markham, Vaughan, Oakville, Burlington due to its cost-effectiveness, minimal disruption, and ability to prevent costly water damage. It's a proactive solution that addresses moisture issues before they escalate, protecting your home's foundation, belongings, and overall health. Flooding in Ontario has caused over $1.2 billion in home insurance claims in just one year (2018), according to the Insurance Bureau of Canada. That’s a huge reason why protecting your basement with interior waterproofing makes sense, especially in the GTA where flooding is a growing problem. (source) 

• Cost effective and address specific issues: Interior waterproofing is a smart and affordable option, especially when digging outside your home isn’t possible. It helps keep your basement dry, improves air quality, and stops mold from growing. This method is highly effective for managing hydrostatic pressure (water seeping up through the floor) and sewer backup, which are common causes of basement flooding in the GTA. Plus, the City of Toronto offers up to $3,400 in rebates to help with the cost.
  City of Toronto Basement Flooding Protection Program
• Convenient for Urban areas: In many GTA homes, the space around the house is tight. You might have a neighbor’s fence, a garden, or a concrete driveway right next to your foundation. Digging outside to fix leaks just isn’t always an option.

That’s where interior waterproofing comes in. It’s done from inside the basement, so there’s no mess outside and no need to ruin your landscaping. It also costs less than exterior work and usually takes less time.

More importantly, it keeps your home healthy. It helps stop:

• Musty smells
• Mold and mildew
• Damp floors and walls

You’ll breathe cleaner air and can even turn your basement into a better storage space or living area.

And here’s the good news, cities like Toronto offer rebates to help cover the cost. If you install things like a sump pump or backwater valve, you can get back up to $3,400 as rebates. That means better protection for your home without breaking the bank.

So, if your basement feels damp or smells musty, interior waterproofing is a smart and supported choice for homes in the GTA.

There are many common signs that you need interior waterproofing includes musty odors, water stains, damp walls, rust on metal items, paint peeling off, powdery deposits on walls, high humidity levels in the basement, swelling on woods after it rains. According to the City of Toronto, flooding and moisture damage are common in older GTA homes, especially those built before the 1970s without modern waterproofing systems.
City of Toronto – Basement Flooding Overview

Your basement is trying to tell you something. If you’ve noticed any of these signs, your home may need interior waterproofing:

• Damp or wet walls and floors
• Musty smells or mold
• Cracks in the walls or floor
• Efflorescence (chalky residue on walls)
• Water coming in during or after a rainstorm
• Warped wood
• Peeling paint
• Condensation on basement windows
• Rust on metal materials 
• Damp carpets or rugs 
• High indoor humidity in the basement
• Dark patches on walls 
• Insects or pests attracted to moisture
• Sump pump running constantly

In many GTA homes, especially older ones, about 20% have seen basement flooding at least once, often after heavy rain or melting snow. So if you're noticing damp walls, musty smells, or even small cracks, it's a clear sign that interior waterproofing could really help. 

The City of Toronto warns that older homes, especially those without sump pumps or proper drainage, are at higher risk of basement flooding and moisture issues. Many homes in the GTA were built before today's waterproofing systems were common. That means water has more ways to get inside.

Interior waterproofing helps fix these problems from the inside, catching water before it spreads. It's not just about stopping a leak, it’s about making your whole home healthier, safer, and better to live in.

If you’re seeing any of these signs, don’t wait until it gets worse. A small fix now can save you from big headaches later.

Interior waterproofing isn’t just plugging a leak, it’s a full system we install inside your basement to stop water before it causes damage. We inspect, seal cracks, dig a small trench, install drainage, apply a wall membrane, and set up a sump pump to safely move water out. Here’s how we do it, step by step.

1.  We Start With a Careful Inspection

First, we visit your home and check the entire basement. We look for signs of moisture, cracks, leaks, stains, and anything that could be causing the problem. This step helps us understand what’s really going on, and what your basement actually needs. No guesswork here.

2.  We Seal the Cracks

If we find cracks in the walls or floor, we seal them using hydraulic cement or epoxy. These materials are super strong and expand slightly as they dry, which helps keep water from sneaking through the same cracks again.

3.  We Cut a Small Trench Along the Basement Walls

This part sounds intense, but it’s not. We use special tools to cut a shallow trench around the perimeter of your basement, right where the wall meets the floor. It’s neat, controlled, and doesn’t damage the rest of your space.

4. We Install Weeping Tile (Drain Pipe)

Next, we place a perforated pipe inside the trench. This pipe collects any water that seeps in from under your floor and redirects it away before it can pool or flood the basement. It’s like giving water an escape route.

5. We Attach a Drainage Membrane to the Wall

To handle wall moisture, we fasten a special dimpled plastic sheet (like Delta MS) to the basement walls. This guides any water that runs down the wall straight into the trench, so nothing gets trapped behind your drywall or insulation.

6. We Refill and Restore the Floor

Once the pipe and membrane are in place, we cover the trench with clean gravel and pour fresh concrete over it. When it’s dry, your basement floor looks smooth and solid again, like we were never there.

7. We Install the Sump Pump

Finally, all the water collected from the system drains into a sump pit, where we install a sump pump. This pump automatically pushes the water out of your house through a discharge pipe. And yes, we can install a battery backup so it still works during power outages, because storms don’t wait for the lights to come back on.

At Canada Waterproofers, we use trusted, long-lasting materials to build a waterproofing system that works from the ground up. From dimpled membranes that guide wall moisture to perforated pipes that collect water under the floor to heavy-duty sump pumps that remove it, we use every layer to protect your basement from leaks, dampness, and mold.

Here are the details to help you understand better:

Dimpled Drainage Membrane Systems

This is the bumpy plastic sheet we install on your basement walls (often known by brands like Delta MS). It creates a small air gap between the wall and the membrane, which allows moisture to flow down freely into the drainage system, instead of getting trapped behind your drywall or seeping into the room. It’s a simple but powerful layer of protection.

Perforated Weeping Tiles + Gravel Filtration

These aren’t tiles in the traditional sense, they’re special plastic pipes with small holes (perforations). We lay them along the edge of your basement floor, and they collect groundwater before it reaches the surface. We surround them with clean gravel, which filters out dirt and helps the system stay clear and free-flowing. This combo does a lot of heavy lifting when it comes to keeping your basement dry.

Sealants, Epoxies, and Concrete Repairs

Before installing anything else, we deal with cracks using hydraulic cement or epoxy injections. These sealants are waterproof, expand as they dry, and bond well with concrete, so the fix lasts. Once the job’s done, we restore the floor with fresh concrete, leaving everything clean and solid again.

High-Quality Sump Pumps (With Optional Battery Backup)

The sump pump is what removes the water from your home. We only install reliable, heavy-duty pumps designed for Canadian basements, ones that work automatically and are built to last. And because power outages are common during storms, we also offer battery backup systems, which kick in if the main power fails.

Interior waterproofing in the GTA usually ranges from $75 to $150 per linear foot, depending on the size of the space, condition of the basement, and type of property, residential or commercial. Most homeowners spend between $3,000 to $15,000, while commercial jobs can go higher. Here’s what really affects the cost and what you can expect if you live anywhere from Toronto to Mississauga, Oakville, Vaughan, Markham, or Hamilton.

Waterproofing isn’t a “one-price-fits-all” kind of job. Some basements need just a bit of sealing, while others need a full drainage system and sump pump setup. We always price based on what you need, not just a standard package.

To get a more clearer picture of what your project might cost, you should try our basement waterproofing cost calculator. This is a great tool to help you budget your plan beforehand. 

What’s the Cost for Residential Properties?

If you own a house, duplex, or small rental, here’s a general idea of interior waterproofing price in GTA:

• Basic sealing or small section repair: $70– $120 per linear foot
• Full interior waterproofing system (with weeping tile, membrane, sump pump): $5,600 – $12,000
• Larger homes or homes with more damage: $10,000 – $15,000+

The average cost per linear foot is around $75 to $150, depending on layout, materials, and extras.

What About Commercial Properties?

Larger spaces like basement offices, commercial units, or multi-tenant buildings need a bigger setup:

• Small commercial jobs: $10,000 – $20,000
• Larger, complex foundations: $20,000 – $50,000+
• Per linear foot, it ranges from $150 to $350, especially if we’re dealing with concrete walls, heavy foot traffic, or special drainage requirements.

We often work with landlords and property managers across the GTA, including areas like Etobicoke, North York, Richmond Hill, Scarborough, and Oakville. Every project is tailored based on building use, floor plan, and foundation conditions.

You can find and use our cost calculator to get a better estimate.

Interior waterproofing doesn’t have to come entirely out of pocket. Many local municipalities across the GTA offer rebate programs to help homeowners protect their basements from flooding. If you're in Burlington, Hamilton, Mississauga, Oakville, Milton, or Brampton, you may qualify for up to $10,500 in financial support.

Check available rebates here!

The cost of interior basement waterproofing in the GTA depends on a few key factors like the size of your basement, how bad the water damage is and the type of methods and materials you choose. If the job is more complex such as adding a sump pump or backwater valve the price will be higher. Labor costs and how deep your foundation is can also change the final cost. Getting quotes from a trusted contractor is important as they can give you a fair estimate and make sure the work is done properly for long lasting protection. 

Here are a few things that can affect the final price:

What We Look At:

• Basement size
  A bigger basement means more space to cover. That means more materials and more time, which can raise the cost.
  
  
• Crack severity
  Hairline cracks are usually easy to fix. But if we find deep or spreading cracks, they may need extra repair before waterproofing can begin.
  
  
• Existing finishes
  If your basement is already finished with flooring or drywall, we may need to remove and put those back after the work. That adds to the labor and time.
  
  
• Ease of access
  Tight corners, cluttered rooms, or tricky layouts can make the job slower and a bit more complex.
  
  
• Age of the home
  Older homes sometimes have outdated or damaged foundation systems. They may need more prep work or stronger solutions.

We take all of this into account when giving you a quote, and we always explain what’s needed and why, no surprises, just honest advice.

Interior waterproofing is a great option for homeowners looking for a cost effective and less disruptive solution. It works well for basements with finished walls since it avoids major exterior digging that can damage landscaping or nearby structures. This method is especially good for stopping water from hydrostatic pressure which pushes moisture up through the basement floor. When paired with a sump pump system it offers strong protection against flooding. Interior waterproofing also helps prevent mold and mildew from forming and keeps the structure of your home safe for years making it a smart long term investment.

When Interior Waterproofing Makes Sense:

• Great for smaller or finished basements
  If your basement is finished or partially finished, interior waterproofing avoids tearing up walls and landscaping from the outside.
  
  
• Faster turnaround time
  Most interior systems are installed in 1 to 3 days, with minimal mess or disruption to your daily life.
  
  
• No need for exterior excavation
  If your home has tight property lines, decks, walkways, or gardens, digging outside isn’t ideal. Interior systems work from inside and skip the heavy machinery.
  
  
• Cost-effective and clean
  It’s generally more affordable than exterior work and restores your basement quickly without disturbing your yard.

Ready to waterproof your basement? Call 416‑333‑2212 or fill out the quick form at info@waterproofing4less.ca to book your free inspection and quote. We proudly serve Burlington, Hamilton, Oakville, Mississauga, Milton, Etobicoke, Brampton, and nearby areas across the GTA.

Water started coming into my basement after heavy rain, and I didn’t know what to do. I called Waterproofing4Less, and they came the next day. The guys were polite, explained things in simple terms, and finished everything in two days. No more water, no more smell, just dry floors. I’m honestly so relieved. Thanks again!
- John D., Brampton

A Note from Team Waterproofing4Less
John’s basement was facing a common problem we see across Brampton, groundwater pushing through foundation cracks after storms. We're happy we could step in quickly, explain the process clearly, and leave his home dry and protected. It’s always rewarding to help good people feel safe in their own space.

Click here and know more about our work and client’s reviews!

Expert Insight – Carl McDowell
When water shows up after rain, it usually means the foundation isn’t draining properly. Interior waterproofing gives that water a way out before it causes real damage. In homes like John’s, it’s the fastest and most reliable fix.

Q1. What is the best waterproofing for interior walls?

A combination of drainage membrane (like Delta MS), sealants (epoxy or hydraulic cement), and weeping tile is best for interior wall waterproofing.

Q2. How much does waterproofing cost in Toronto?

Interior waterproofing in Toronto typically costs $75–$150 per linear foot

Q3. Can waterproofing be done from inside?

Yes, interior waterproofing is a clean, effective method done entirely from inside the basement

Q4. Is interior waterproofing worth it?

Yes, it’s cost-effective, less invasive, and helps protect your home from long-term moisture damage.

Q5. How does interior basement waterproofing work?

It redirects water through drainage systems inside your basement and expels it using a sump pump.

Q6. Which is better, interior or exterior waterproofing?

Interior waterproofing is better for finished basements or tight spaces, while exterior is ideal for full foundation protection.

Q7. Can we paint over waterproofing?

Yes, once the waterproofing layer is fully dry and cured, you can paint over it with compatible products.

Q8. What is the lifespan of waterproofing?

We at waterproofing4less offer 25 years of warranty.

Andrii Lema is a seasoned Waterproofing & Drain Expert at Waterproofing4Less, with over a decade of experience across Toronto, Mississauga, Oakville, Hamilton, and Burlington. Specializing in sump pump installations, backwater valve systems, basement waterproofing, and drain repair & replacement, Andrii combines local code expertise with advanced techniques to deliver reliable, long-lasting solutions.