- Updated: October 03, 2025
Nico Barbieri
Nico was the first person hired for the position of estimator and project manager for our growing company. He has over 25 years of experience in the water proofing industry. More About Nico
Underpinning your basement means reinforcing or extending the foundation of an existing home to increase stability, correct structural issues, or allow for modifications like lowering the basement floor. It’s a major project but can unlock significant benefits — more usable space, better structural integrity, and increased property value. If you’re in Toronto and considering basement underpinning, here’s what you need to know.
What Is Basement Underpinning?
- Definition: Underpinning is the process of strengthening and deepening a foundation beneath an existing structure. It often involves digging below the current footing and adding new supports or footings.
- Purposes:
- Fix foundation damage (cracks, settling).
- Address soil changes or instability.
- Comply with updated building codes or retrofit requirements.
- Increase basement ceiling height or create more usable basement space.
- Fix foundation damage (cracks, settling).
Why You Might Need Underpinning
| Common Trigger | What Happens Without Underpinning |
| Foundation cracks or noticeable settling | Water infiltration, structural movement, damage to walls/floors. |
| Soil shifts, expansive clay, poor soil quality | Foundation instability, risk of sinkage or uneven floors. |
| Need for new basement configuration (rooms, windows, height) | Low headroom, limited finishing options, cramped spaces. |
| Changes in regulations/building codes | Older homes may no longer meet current safety or structural standards. |
Underpinning Methods Commonly Used in Toronto
Here are some of the typical underpinning techniques that contractors may use, depending on the situation:
- Sectional excavation / beam & base support – sections of wall are successively supported by steel beams or concrete footings.
- Piering / concrete/micropiers – vertical supports driven or drilled to stable soil or bedrock.
- Slab-underpinning / full-slab excavation – removing the existing slab and digging deeper for a full height basement or to raise ceiling height.
- Mass concrete underpinning – large concrete blocks installed below the existing foundation in stages.
How the Underpinning Process Usually Works
Here’s a standard process homeowners can expect:
- Structural Assessment & Soil Survey
- A structural engineer inspects foundation condition, soil composition, groundwater levels.
- Permits and architectural/engineering plans are prepared.
- A structural engineer inspects foundation condition, soil composition, groundwater levels.
- Site Preparation
- Protection of existing structure, utilities, landscaping.
- Safety measures in place; temporary supports if needed.
- Protection of existing structure, utilities, landscaping.
- Excavation & Footing Installation
- Small sections (or bays) are excavated under or adjacent to existing foundations.
- New reinforced footings or piers are installed.
- Small sections (or bays) are excavated under or adjacent to existing foundations.
- Lowering Basement Floor (if applicable)
- Removal of existing slab and fill material.
- Installation of moisture barrier, drainage, and new slab.
- Removal of existing slab and fill material.
- Waterproofing & Drainage
- Underpinning must include waterproofing (membranes, coatings) and proper drainage (interior or exterior) to ensure water does not weaken the new foundation.
- Underpinning must include waterproofing (membranes, coatings) and proper drainage (interior or exterior) to ensure water does not weaken the new foundation.
- Finishing & Restoration
- Repair walls, flooring, windows.
- Restore landscaping and any exterior surfaces disturbed.
- Repair walls, flooring, windows.
Key Risks & Things to Watch Out For
- Structural risk: Poor underpinning or lack of professional engineering can lead to wall cracks, shifting, or failure.
- Moisture & water issues: Without proper waterproofing and drainage, new foundation work can trap or attract water.
- Permit & regulatory compliance: Required by law — inspections must be passed. Failing to get permits can lead to legal or resale issues.
- Cost & timeline variability: Projects can be expensive and take time—unexpected soil, access issues, or weather may cause delays.
- Disruption: Noise, dust, possible temporary relocation depending on extent of work.
Is Underpinning Right for Your Toronto Home?
You should consider underpinning if:
- Your basement ceiling height is low and you want livable space.
- You notice cracks in foundation walls or uneven/sloping floors.
- Soil tests revealed poor soil bearing capacity or shifting.
- You plan to install egress windows, enlarge windows, or need more natural light.
- You want to protect your home from long-term structural damage and increase resale value.
A structural engineer or experienced underpinning contractor can evaluate feasibility, cost, and risk for your specific home.
FAQ (Common Questions Homeowners Ask)
Costs depend on size, depth, soil conditions, access, finishing, and how much waterproofing is necessary. Get multiple detailed quotes.
For a typical project, from assessment through restoring finishes, expect several weeks to a few months depending on complexity.
Only if waterproofing and drainage are neglected. Proper design, barriers, and sump pump systems are crucial.
Yes, under proper engineering, quality materials, and regular maintenance, underpinning can last for many decades.
Conclusion
Underpinning is a powerful way to stabilize and upgrade your home — especially in Toronto where many older homes need structural reinforcement or want more usable basement space. If you think your home might benefit from basement underpinning, begin with a structural assessment and detailed quotes from experienced contractors. Aquatech Basement Waterproofing has decades of experience in underpinning and foundation work — reach out for an evaluation or quote tailored to your home.
