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

    Why does my basement leak during spring thaw?

    Snowmelt on frozen or saturated ground is the Ontario season when perimeter drains get overloaded.

    Basements that leak in the Ontario spring thaw are taking on snowmelt while the ground is still frozen or saturated, so water runs to the foundation. Frozen weeping tile, icy downspouts, full window wells, and grading toward the house are the common causes. A March or April leak is still a drainage problem.

    Where the water shows up

    What you seeLikely cause
    Leak as snow disappearsMeltwater against frozen or saturated soil
    Downspout splash at the wallBuried extension frozen or disconnected
    Window well full of ice meltWell drain blocked or missing
    Same leak every thaw, dry in summerSeasonal overload of the perimeter drain

    What to do now

    Clear snow away from the foundation where you can do it safely, open downspout extensions, and empty window wells. Photograph the entry point. Do not chip ice against the foundation wall.

    When to call a contractor

    Call if thaw water enters living space, if the sump runs constantly and cannot keep up, or if this is the second spring with the same leak. Exterior digging waits for thawed ground; interior drainage and crack injection do not.

    Start with the provincial guide water in the basement, then the Ontario cost hub.

    Local basement waterproofing guides

    Can you waterproof a basement in winter in Ontario?

    Interior systems and crack injection can be done in winter. Exterior excavation generally waits until the ground thaws. Stopping the water path can still start with downspouts, grading, and a diagnosis before spring.

    Does a spring-only leak need exterior waterproofing?

    Not always. A thaw leak can be surface water from grading and downspouts. Exterior waterproofing is the conversation when the perimeter drain has failed or the wall stays wet after the surface water is fixed.

    Resources & guides

    Practical articles on moisture, foundations, and keeping water out of Ontario homes.

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