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    Ontario home illustrating water protection from roof leaks through foundation and drainage — Waterproof Ontario.

    Interior Waterproofing in Ontario

    Collect water at the footing and move it out with a drain and sump, without digging up the yard.

    Interior waterproofing manages water after it reaches the foundation. A perimeter drain is installed inside the basement along the footing, and it carries the water to a sump pit. A pump then moves the water out through a discharge line.

    It is the option most often chosen when excavating the outside is not practical. It does not stop water pressure from reaching the wall, so the drain and sump have to be designed and maintained properly.

    What an interior system includes

    A complete interior system has a few parts that each need to be specified in the quote. The drain collects water at the footing, the sump holds it, and the pump moves it to the discharge point.

    • Perimeter drain along the footing, with the floor cut and restored.
    • Sump pit and a primary pump, with a check valve and discharge line.
    • Battery backup or a second pump, where power loss or heavy rain is a risk.
    • Discharge that runs away from the foundation, not back toward it.

    Planning costs

    Interior drainage with a sump is commonly planned at $5,000–$12,000 CAD, before tax. That range is a planning figure from our basement leak repair guide. The final price depends on the perimeter length, floor type, pump choice, and how much finishing the homeowner wants.

    Sump installation on its own is often a smaller job. See the sump pump installation pages for city-specific ranges.

    When interior is the better route

    Interior systems are a fit when the outside is blocked by a deck, a finished patio, a property line, or a deep footing. They are also used when the water problem is limited to certain walls.

    If the main issue is a single active crack, crack repair may be enough. Ask the contractor to explain why the proposed route suits your home.

    Maintenance and warranties

    A sump pump needs to be tested and kept clear. Pumps and batteries have a limited life, so the quote should state the warranty on each part and how the pump will be maintained.

    Interior waterproofing: what a good scope includes

    Interior systems manage water after it reaches the foundation. A good scope shows where the water is collected, where the pump discharges, and how the pump is protected.

    • Ask where the perimeter drain connects to the sump and where the pump discharges, in writing.
    • Confirm whether a battery backup or a second pump is included, and who services it.
    • Ask how the crew will cut and restore the floor, and whether the price includes finishing.
    • Get the warranty split between labour and equipment, since they often run on different timelines.

    Prices in CAD. See the full 2026 Ontario cost hub for roof-to-foundation bands, basement city ranges, and the basement calculator.

    Common questions

    Interior systems do not stop water pressure from reaching the wall. They collect the water at the footing and move it to a sump, so it stays out of the living space. Exterior waterproofing is the option that stops water at the wall.

    It is often chosen when excavating the outside is not practical, such as when landscaping is finished, the foundation is close to a property line, or the footings are deep. A contractor should explain why the interior route fits your home.

    Lifespan depends on the materials, the installation, and the sump and pump. Pumps need periodic testing and eventual replacement. Ask for the warranty terms and the maintenance schedule in the quote.

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