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DEEPLINEWATERPROOFING
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Exterior foundation wall coated with waterproofing membrane and dimple sheet in an open excavation, Toronto
Basement Waterproofing

Two Ways to Keep Water Out. Here's How to Choose.

One method stops water before it touches your foundation. The other lets it arrive and then pumps it away. They cost very different amounts and they are not interchangeable.

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Basement waterproofing comes in two forms, and the difference between them is where the water gets stopped: outside the foundation wall, or after it has already reached the inside.

Exterior basement waterproofing costs $150 to $300 per linear foot and stops water before it enters the foundation. Interior waterproofing costs$80 to $150 per linear foot and collects water at the footing once it is through, routing it to a sump pump. A full interior system runs$8,000 to $15,000; a full exterior perimeter runs$15,000 to $35,000.

The two methods, side by side

Interior versus exterior basement waterproofing, shown in cutaway Two cutaways of the same foundation wall. Exterior waterproofing excavates the outside of the wall, applies a membrane and dimple board to the outside face, and lays new weeping tile in gravel beside the footing, so water is stopped before it reaches the wall. Interior waterproofing breaks the slab inside, lays a drain pipe beside the footing inside, and routes water to a sump pump, so water passes through the wall and is then collected and pumped out.Exterior WaterproofingStops water before it reaches the wallGradeexcavated, then backfilledinsidegroundwaternew weeping tilein clear stonemembrane +dimple boardWater never enters the wall. Requires fullexcavation to the footing, outside.Interior WaterproofingCollects water once it is through, and pumps it outundisturbed — no excavationgroundwaterpumped outWater passes through the wall, then is caughtat the footing and pumped to the sump.$150 – $300 per linear foot · $15,000 – $35,000 full perimeter$80 – $150 per linear foot · $8,000 – $15,000 full system
The same wall, treated two ways. Exterior work keeps water out of the structure entirely but requires digging to the footing. Interior work lets water reach the wall and then manages it, at roughly half the cost and with no excavation outside. Neither is universally correct — see the comparison below.

Exterior work is the more complete fix. The wall itself never gets wet, which matters for block foundations where saturated cores lead to spalling and efflorescence over time.

Interior work is roughly half the price and does not touch your landscaping, driveway, deck or side yard. It also works in places where excavation is simply impossible, which in Toronto is a large number of houses.

When exterior is the right call

When you can actually dig. A detached house with a clear side yard and no deck, patio or mature planting over the foundation is a straightforward exterior job.

When the foundation is block rather than poured concrete, because block absorbs and holds water in a way poured walls do not.

And when the wall is already coming up for other reasons — if you are replacing weeping tile or repairing a structural crack from outside, doing the membrane at the same time costs far less than a second mobilisation later.

Full detail on the method, materials and sequence is onexterior waterproofing in Toronto.

When interior is the right call

When the side yard is three feet wide and shared with the neighbour, which describes a great deal of Toronto's semi and row housing.

When there is a deck, an interlock patio, a driveway or thirty years of garden over the foundation, and the cost of reinstating all of it exceeds the saving from working outside.

And when the budget is the binding constraint. An interior system at$8,000 to $15,000 that actually gets installed is worth more than an exterior system at $15,000 to $35,000 that stays a quote.

The method, and what a proper installation includes, is oninterior waterproofing in Toronto.

Before you buy either one

A surprising share of wet basements do not need a waterproofing system at all.

Downspouts discharging against the wall, negative grading, a failed window well, a cracked cold cellar, or a single foundation crack are all cheaper problems that present with identical symptoms.

Crack injection is $450 to $1,100 per crack. A window well drain is$500 to $1,500 per window. Regrading is often a day's work. Any contractor who quotes a full perimeter system before establishing where the water is entering is selling, not diagnosing — and that is the subject ofwet basement repair.

What it costs

WorkToronto 2026 range
Interior membrane and drain channel$80 to $150 per linear foot
Exterior membrane waterproofing$150 to $300 per linear foot
Full interior drainage system$8,000 to $15,000
Full perimeter exterior$15,000 to $35,000
Crack injection, per crack$450 to $1,100 per crack
Window well drain, per window$500 to $1,500 per window
Verified Toronto market ranges for 2026. These are market ranges rather than a quote for a specific house.

A full line-by-line breakdown, including what drives a job to the top of each range, is on theToronto waterproofing cost page.

Basement Waterproofing: Common Questions

Should I waterproof my basement from the inside or the outside?

Exterior waterproofing stops water before it enters the foundation and is the more complete fix, at $150 to $300 per linear foot. Interior waterproofing lets water reach the wall and then collects and pumps it out, at $80 to $150 per linear foot. Choose exterior when you can excavate and want the wall itself protected; choose interior when access, cost, or a finished landscape rules out digging.

How much does basement waterproofing cost in Toronto?

A full interior drainage system runs $8,000 to $15,000. A full exterior perimeter runs $15,000 to $35,000. Per linear foot, interior work is $80 to $150 per linear foot and exterior is $150 to $300 per linear foot. Single crack injection, where the leak is one crack rather than a system failure, is $450 to $1,100 per crack.

Is basement waterproofing covered by the City of Toronto subsidy?

No. The Basement Flooding Protection Subsidy covers specific devices only: backwater valves, a sump pump, battery backup, weeping tile severance and capping, and a plumbing assessment. Interior and exterior waterproofing systems receive nothing. Any contractor advertising "save up to $6,650" beside a waterproofing quote is conflating two different things.

How long does basement waterproofing last?

A properly installed exterior membrane and drainage system is generally expected to last the life of the foundation. Interior systems depend on a sump pump, which is a mechanical device with a service life measured in years rather than decades. The pipe and stone in either system fail early only when filter fabric was omitted and the pipe silted up.

Do I need to waterproof if my basement is only damp, not wet?

Not necessarily. Persistent damp with no visible water is often a humidity and ventilation problem rather than a groundwater problem, and a dehumidifier solves it for a few hundred dollars. Water staining at the floor-wall joint, efflorescence on the block, or seasonal pooling are different signals, and those do indicate a drainage failure.

Not sure which method your house needs?

We find where the water is actually getting in before recommending anything. Often the answer is cheaper than a full system.

Call (647) 584-9600Book a Free Assessment
Call (647) 584-9600