Quick answer: interior waterproofing typically runs $3,500 to $14,000 depending on how much of the basement perimeter needs a system. It's the right call when water is already getting past the foundation and excavating the yard isn't practical.
When a basement takes on water and full exterior excavation isn't an option, because of mature landscaping, an attached garage, a shared wall, or a deck built over the problem area, interior waterproofing gives you a system that intercepts water before it reaches your floor and routes it to a sump pump instead of your carpet.
It manages water, rather than stopping it at the source the way exterior waterproofing does. That distinction matters for setting the right expectation before work starts.
What Interior Waterproofing Actually Involves
The core of the system is a drainage channel installed along the interior of the footing, at the point where the foundation wall meets the floor. That channel ties into a sump pump and pit, which pumps collected water outside and away from the house. Depending on the basement, we also install a vapour barrier or dimple board against the wall and seal the cove joint before the system is tested under real water conditions and closed up.
Pricing scales with how much of the perimeter needs coverage. A partial system addressing one problem wall typically runs $3,500-$5,500. A full-perimeter system in a larger basement runs $9,000-$14,000, and adding a sump pump and pit where none exists adds another $1,500-$3,000.
How the Process Runs
Assess the Water Source
We confirm whether water is coming through the floor-wall joint, a wall crack, or both, since that determines the right system.
Install the System
Drainage channel, sump pump integration, and vapour barrier installed along the affected perimeter.
Test & Final Seal
The system is tested under real water flow before the area is closed up and finished.
When Interior Waterproofing Isn't the Right Fit
If water is entering through a visible foundation crack rather than seeping along the floor-wall joint, sealing that crack directly is often a smaller, more targeted fix than a full interior system. And if the real problem is exterior grading pushing water against your foundation in the first place, exterior waterproofing addresses the cause instead of just managing the result. We'll tell you which situation you're in before recommending either.
Frequently Asked Questions
What's the difference between interior and exterior waterproofing?
Exterior waterproofing stops water at the foundation wall from the outside, which requires excavation. Interior waterproofing manages water after it's already gotten through, using an interior drainage channel and sump pump to redirect it before it reaches your floor. Interior is faster and less disruptive, but it manages the water rather than stopping it at the source.
How much does interior waterproofing cost?
A partial-perimeter system for a small area typically runs $3,500-$5,500. A full-perimeter system in a larger basement runs $9,000-$14,000. Add $1,500-$3,000 if a sump pump and pit aren't already in place.
Will interior waterproofing stop water from entering my walls?
It stops water from reaching your floor and finished space, but it doesn't seal the foundation wall itself. If the wall is actively leaking through a crack rather than seeping through the floor-wall joint, that crack needs to be addressed directly, sometimes alongside the interior system.
Do I need a permit for interior waterproofing?
Generally no, since the work doesn't change your home's structure or footprint. A permit becomes relevant only if the project is bundled with underpinning or a full basement renovation.
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