Basement Underpinning Services
Professional Foundation Support as Part of the Basement Lowering Process
Underpinning strengthens and extends the basement foundation so your basement can be safely lowered to achieve more headroom, better structural stability, and room for a new concrete floor. Strong Basements Inc. completes every underpinning project with engineered drawings, Toronto building permits, and full Ontario Building Code compliance.
Contents
What Is Underpinning?
Foundation Underpinning involves installing a new footing beneath or beside the existing foundation to safely support the structure during basement lowering. It is the core stage of the basement lowering process, completed before waterproofing, new drainage systems, insulation, and the new concrete floor.
Underpinning Construction Process
We prepare the basement by installing conveyor belts, disposal bins, shoring posts (if required), lighting, and dust barriers. Mechanical systems like HVAC or water heaters may be suspended to remain functional during work.
The walls are divided into engineered sections, spaced to keep the home fully supported while each stage is completed.
We excavate the first group of sections to the required depth, including space for gravel bedding and the future concrete slab. Portions of the existing footing may be removed depending on the chosen method.
A structural engineer inspects the prepared sections, checking soil conditions, depth, and footing preparation before concrete installation.
Wood forms or rebar structures are installed, and new concrete is poured into the first-stage sections. Curing takes 24–48 hours.
The second set of underpinning sections is excavated to the required depth, cleaned, and prepared for forming. Before any concrete is poured, a City of Toronto building inspection is performed, just like in the first stage, and the work must pass this inspection to continue. Once approved, the sections are formed and poured following the engineered plan. A structural engineer’s report is not required for this stage unless specified in the drawings.
The final underpinning sections are excavated, followed by complete basement excavation to the new lowered height across the entire floor area. Before any forming or concrete work begins, a City of Toronto building inspection is performed, and the stage must pass this inspection just like in the first two stages. Once approved, the project can proceed to forming and pouring the final sections.
Forms and concrete are installed for the final sections. Rebar installation may occur either before or after inspections, depending on the engineering plan.
Underpinning basement with us
- Free Estimates
- Planning & Permitting
- Management & Construction
- Service & Suppor
- Warranty
Types of basement Underpinning We offer
A full-width concrete footing is poured beneath the existing foundation, then allowed to cure for 24–48 hours. After curing, a 2–3 inch gap is filled with non-shrink grout to create a solid, long-term bond between the new footing and the original wall. This is one of Toronto’s most reliable underpinning methods for basement lowering.
Part of the original footing is removed, and new concrete is poured to overlap the foundation wall, creating a wider and stronger structural base. The concrete is placed using a concrete vibrator to ensure full settlement and to eliminate air bubbles, improving strength and long-term performance. This is the fastest and most efficient underpinning method for older Toronto homes.
The existing footing is partially or entirely removed. A reinforced L-shaped underpinning section is built flush with the original foundation wall and anchored into the footing, allowing the new support to tie directly into the structure. This method keeps the interior walls straight and maximizes usable basement space, making it ideal for narrow or tight layouts.
Bench underpinning is used when digging under the existing footing is not allowed or not safe, such as along party walls without neighbour consent or where an adjacent foundation is too close. Instead of supporting the structure from underneath, this method builds a reinforced concrete bench beside the original footing.
Basement Underpinning Cost
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Non-Shrink Underpinning $380+Per linear foot of underpinned basement foundation. Includes: Demolition, Excavation, Disposal, Forming, Concrete, Non-Srink Grout Application, Call and Pass Building Inspections.
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Overpour Underpinning $350+Per linear foot of underpinned basement foundation. Includes: Concrete Demolition, Excavation, Disposal, Forming, Concrete, Call and Pass Building Inspections.
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L-Shape Underpinning $420+Per linear foot of underpinned basement foundation. Includes: Concrete Demolition, Excavation, Disposal, Steel Rebar Reinforcement, Forming, Concrete, Call and Pass Building Inspections.
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Bench Underpinning $420+Per linear foot of underpinned basement foundation. Includes: Concrete Demolition, Excavation, Disposal, Steel Rebar Reinforcement, Forming, Concrete, Call and Pass Building Inspections.
Do I need a Permit for Basement Underpinning?
Yes, a building permit is required for basement underpinning in Toronto. Underpinning changes the structural support of your home, so the city requires architectural drawings, structural engineering plans, zoning verification, and scheduled inspections throughout the project. The permit ensures that all excavation and foundation work follows the Ontario Building Code and is safe for both your home and neighbouring properties. At Strong Basements Inc., we work with trusted engineers to prepare all documents and handle the permit process from start to finish, so your basement lowering project moves forward smoothly and compliantly.
IN TECH HOUSE DESIGN (ITHD) is our trusted architectural and engineering partner, which provides homeowners with zoning bylaws, surveys, design, architecture, engineering, and building permits.
Basement Underpinning Faq
Underpinning is the process of adding a new concrete footing under or beside the existing foundation to support the structure during basement lowering. It strengthens the foundation, allows deeper excavation, and prepares the basement for waterproofing, drainage upgrades, and a new concrete floor.
A typical residential project takes 3–4 weeks, depending on the number of underpinning sections, soil conditions, basement size, and the type of underpinning used (non-shrink, overpour, L-shape, or benching).
Yes. Underpinning requires a City of Toronto building permit, engineered drawings, and multiple inspections. The drawings must include architectural plans, structural plans, drainage layout, and zoning compliance.
We provide four engineered underpinning methods in Toronto, Ontario:
Non-Shrink Underpinning
Overpour Underpinning
L-Shape (Flush-With-Wall) Underpinning
Bench Underpinning
Each method is selected based on soil conditions, foundation design, neighbour permission, and available space.
No. Bench underpinning does not support the house from underneath. Instead, it creates a concrete bench beside the existing footing. It’s used when the wall cannot be underpinned — often due to neighbour permission issues on shared or close foundations.
Most Toronto basements can be lowered to achieve a finished ceiling height of 7 to 8 feet, depending on soil conditions, the existing foundation, and city requirements. The maximum depth of a single underpinning stage is 4 feet, which means we can safely lower the basement up to four feet from the original floor level in one sequence. If the project requires going deeper than 4 feet, the basement must be underpinned twice, following a second engineered plan and permit. Your structural engineer will confirm the safe excavation depth for your specific home.
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TORONTO BUILDING RENOVATOR LICENSE: T85-4754041
TORONTO PLUMBING CONTRACTOR LICENSE: T94-4891681
Underpinning Pictures
