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Waterproofing & Drainage

Basement Waterproofing in the GTA

Water gets into Ontario basements the same few ways every time: through foundation cracks, over the top of the footing when the weeping tile has silted up, around window wells that hold water like buckets, or backwards up a floor drain during a big storm. The fix depends entirely on which one you've got — which is why 'waterproofing' quoted without a diagnosis is guesswork.

Interior systems manage water that arrives: a membrane on the wall, drainage channel at the footing, and a sump pump to carry it out. Exterior waterproofing stops water before it touches the foundation: excavation, a proper membrane and new weeping tile. Exterior costs more and fixes more; interior is often the practical answer where excavation isn't realistic. Plenty of houses need something far simpler first — downspouts extended, grading corrected, one crack injected.

If you're planning to finish the basement, do this first. Every dollar of waterproofing spent before drywall goes up saves several after. Send photos of where the water shows up — the stains tell us a lot before we even visit.

What this covers

  • Diagnosis of where the water is actually coming from
  • Foundation crack injection from inside
  • Interior membrane and drainage systems with sump pit and pump
  • Exterior excavation, membrane and weeping tile replacement
  • Window well drainage and covers
  • Sump pump installation, replacement and battery backup
  • Downspout extensions and grading corrections
  • Backwater valve coordination where sewer backup is the issue
  • Humidity and moisture-control advice for the space you have

Just need one small job done?

Extend downspouts away from the foundation

What affects the price

  • Interior versus exterior approach — excavation is the biggest cost variable
  • How much of the perimeter is affected — one wall or all four
  • Depth of the foundation and what's in the way outside (decks, additions, driveways)
  • Whether a sump pit and pump already exist or need to be added
  • Access — tight lot lines between houses make exterior work harder
  • The finish inside — working behind finished walls adds demolition and rebuild
  • Municipal subsidy programs for sump pumps or backwater valves, where your city offers them

Every basement is different, so we don’t publish flat prices — the quote is free and based on your actual job.

Basement Waterproofing near you

We take quote requests across the GTA and Golden Horseshoe. Local pages:

TorontoMississaugaBramptonCaledonVaughanMarkhamRichmond HillNewmarketAuroraKingWhitchurch-StouffvilleEast GwillimburyGeorginaPickeringAjaxWhitbyOshawaClaringtonUxbridgeScugogOakvilleBurlingtonMiltonHalton HillsHamiltonSt. CatharinesNiagara FallsGrimsbyKitchenerWaterlooCambridgeGuelphBarrieInnisfilBradford West Gwillimbury

Common questions

Is interior or exterior waterproofing better?
Exterior stops water from reaching the wall at all, which is the gold standard — but it means excavation, and on a tight city lot or under a deck that's a big undertaking. Interior systems accept that some water arrives and manage it reliably to a sump. The right answer depends on your foundation, your lot and your budget; sometimes it's a mix.
A crack in my basement wall leaks every spring. Is that serious?
Usually it's a shrinkage crack — common in poured foundations and fixable with injection from the inside in a couple of hours. What deserves more attention is a crack that's wide, horizontal, or growing, which can signal structural movement. Photos of the crack with something for scale tell us most of what we need.
Do I need a sump pump?
If your basement has a history of water, or you're installing interior drainage, yes — and a battery backup is worth serious thought, because the storms that flood basements are the same ones that knock out power. Several Ontario municipalities run subsidy programs for sump pumps and backwater valves; we'll flag it if yours does.
Can I just seal the wall with paint-on waterproofer?
Coatings have their place on damp walls, but they don't stop water under pressure — hydrostatic pressure will push moisture through or around a surface coating. If water is actively entering, the fix is at the crack, the drainage, or the exterior. We'll tell you honestly if a cheap fix is enough for your situation.
How disruptive is interior waterproofing?
It's concrete work — a trench cut at the slab edge, so it's noisy and dusty for a few days, and anything finished along those walls comes off first. A typical single-wall interior system is measured in days, not weeks. Full-perimeter jobs take longer but follow the same rhythm.

Ready to sort out your basement waterproofing?

Tell us what your home needs — a small fix or a full project — and get a free quote.

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