💧 Basement Waterproofing: what it costs in the GTA (2026)

Ninety percent of wet basements start outside at grade level: downspouts dumping at the wall, soil sloped toward the house, window wells without drainage. Toronto clay holds water against your foundation like a sponge, and hydrostatic pressure pushes it through any crack, cold joint, or tie-rod hole it finds. Before anyone sells you excavation, fix the cheap stuff: extend downspouts 6 feet, regrade the first 6 feet of soil away from the wall, clean the wells. Sometimes that's the whole cure.

Exterior means excavating to the footing, membraning the wall, and new weeping tile: the gold standard, and the expensive, landscaping-destroying one. Interior means a perimeter channel under the slab edge routing water to a sump: less invasive, works in any season, and handles most GTA situations at $70–$120 per linear foot. Interior doesn't stop water entering the block; it manages it before it reaches your floor. For a finished basement in clay soil, managed and dry beats theoretical and perfect.

Hairline vertical shrinkage cracks in poured concrete are near-universal and mostly cosmetic; they get injected with polyurethane from inside in an afternoon. Horizontal cracks, stair-step cracks in block walls, or any crack you can fit a coin in are structural conversations, not DIY injection kits. Width matters less than pattern and change: mark the ends with pencil and a date. If it grows, call. If it weeps but doesn't grow, injection plus drainage usually closes the case.

A sump is your basement's last line, and it fails silently until the storm you needed it. Test it every spring: lift the float or pour a bucket in; it should kick on in seconds and shut off clean. Add a battery backup if your area browns out in storms, which is exactly when you need pumping. Worth knowing: several insurers discount for backwater valves and sump backups, and some GTA municipalities run subsidy programs for them. Ask before you buy; it's real money back.