Underpinning is the process of extending your existing foundation to a lower depth — allowing you to lower the basement slab and gain headroom. Many Toronto and GTA homes, especially pre-war and post-war bungalows, have basements too low for legal secondary suites or comfortable living space. Underpinning solves that.
Underpinning is the process of extending your existing foundation to a lower depth — allowing you to lower the basement slab and gain headroom. Many Toronto and GTA homes, especially pre-war and post-war bungalows, have basements too low for legal secondary suites or comfortable living space. Underpinning solves that.
Our crews work across Toronto and all 30 GTA municipalities — we know the local permit offices, soil conditions, and site constraints that affect your project.
Every underpinning project requires a structural engineer to assess the existing foundation, soil conditions, and design the underpinning sequence and new footing depth.
Underpinning requires a Building Permit. Toronto Building requires a full package: site plan, structural drawings, engineer stamp, and often a geotechnical report.
We excavate in alternating sections beneath the existing footing — typically 3–4 foot wide bays — never undercutting the footing continuously until the previous bay has been poured and cured.
Each excavated section is formed, reinforced with rebar, and poured to the engineered specification. Pours cure before adjacent sections are excavated.
Once all underpinning is complete and inspected, the existing basement slab is removed and the floor is excavated to the new finished elevation.
A new reinforced structural slab is poured at the lowered elevation, incorporating waterproofing membrane, insulation, and radiant heat rough-in if required.
Underpinning and basement lowering requires a Building Permit in Toronto and all GTA municipalities. A Structural Engineer's drawings and stamp are mandatory. Toronto Building also requires inspections at footing, framing, and final stages. Permit timelines: 6–12 weeks in Toronto. Start your application early.
Permit requirements vary by municipality and scope. We'll identify what's required during the site visit and advise on expected timelines.
Prices below are typical ranges for work in the Toronto and GTA market. Actual costs depend on site conditions, access, scope, and permit requirements. All quotes are provided in writing after a site visit.
| Scope | Typical Range |
|---|---|
| Underpinning only (per linear foot) | $250 – $400/lf |
| Full basement lowering — Toronto semi (avg) | $35,000 – $55,000 |
| Full basement lowering — detached home (avg) | $45,000 – $75,000 |
| Bench footing option (less headroom gained) | $18,000 – $32,000 |
| Waterproofing add-on | $8,000 – $18,000 |
All prices exclude HST, permits, and hazmat abatement (if required). Site conditions affect final cost.
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We'll review your request and call you within 2 hours to discuss the project. Most quotes are completed on-site within 24–48 hours.
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