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Basement Underpinning

Toronto Basement Underpinning

We provide expert basement underpinning services across the GTA, safely lowering your floor to achieve the ceiling height you need for a functional, high-value living space. Specializing in old Toronto homes and structural foundation work.

Goral Concrete five star
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🏠Toronto Basement Underpinning & Lowering

Basement underpinning is a strategic investment for Toronto homeowners, transforming cramped, low-ceiling basements into valuable, livable spaces or reinforcing an aging foundation. This guide provides all the essential information for your project.

🔑 What is Basement Underpinning?

Underpinning is a specialized construction process that deepens and strengthens an existing foundation by constructing new footings beneath the old ones.

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  • Goal 1: Increase Ceiling Height (Basement Lowering): This is the most common reason in Toronto's older homes, creating legal, comfortable 7ft or 8ft basement ceilings.

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  • Goal 2: Structural Stabilization: To fix foundation issues like shifting, settling, or cracking caused by soil changes or aging.

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  • Goal 3: Prepare for Additions: To support extra weight from new storeys or structural changes above.

🛠️ The Underpinning Process: Step-by-Step

A professional underpinning project follows a strict, sequential process to maintain the safety and structural integrity of your home at all times.

 

 1. Planning & Permits (The Foundation) 

 

  • Structural Assessment: A licensed Structural Engineer inspects your existing foundation, soil composition, and neighboring properties (especially semi-detached or zero-lot-line homes). 

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  • Engineering Drawings: The Engineer designs and stamps detailed structural plans, including the precise depth, new footing size, and sequencing of work.

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  • City of Toronto Building Permit: A permit is mandatory for all underpinning work. Your contractor or engineer will submit the necessary forms, including:

    • Application to Construct or Demolish Form.

    • Structural Drawings sealed by a Professional Engineer.

    • Commitment to General Reviews (required when digging near adjacent footings or in poor soil).

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  • Timeline Note: Permit approval can take anywhere from 2 to 8 weeks depending on completeness and city review complexity.

 

 2. Preparation & Demolition (The Setup) 

 

  • Site Protection: All main floor access points, floors, and furniture are protected from dust and construction traffic.

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  • Basement Clear-out: The basement is fully emptied. Homeowners may need to arrange for temporary living accommodations during parts of the process.

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  • Existing Slab Removal: The old concrete basement floor is broken up and removed.

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  • Initial Excavation: Soil is excavated to the depth of the existing footings to prepare for the structural work.

 

 3. Structural Underpinning (The Core Work) 

 

  • Sequential Digging (The Bay Method): The foundation wall is divided into numbered sections (bays). Only one-third to one-quarter of the wall is worked on at a time to ensure continuous support.

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  • Excavation: Workers carefully dig beneath the existing footing to the new, lower depth specified in the engineering plans.

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  • Forming & Reinforcement: A wooden form is built, and steel rebar is installed into the excavated area for reinforcement.

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  • Concrete Pour: New high-strength concrete is poured into the form to create a deeper footing.

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  • Curing & Grouting: The new concrete cures for 24-48 hours. Non-shrink grout is applied to seal the joint between the new and old foundation.

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  • Repetition & Inspections: This process is repeated for the remaining sections in sequence (e.g., Section 1, then 2, then 3), with mandatory City Inspections at key stages (e.g., after the first bay is dug, and before concrete is poured).

 

 4. Finishing Systems (Long-Term Protection) 

 

  • Waterproofing: Essential for the longevity of your new basement. This typically involves applying a waterproofing membrane/coating to the new interior walls.

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  • Drainage Systems: Installation of an interior perimeter drain (weeping tile) and a new sump pump system to manage groundwater and prevent hydrostatic pressure.

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  • New Plumbing/Drainage: The sanitary drains and water service line are often too high for the new floor and must be lowered and replaced (typically PVC/ABS piping).

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  • New Concrete Slab: A gravel base, vapour barrier, and new reinforced concrete floor slab are poured at the finished height.

🧱 Underpinning Variety & Custom Options

The right method depends on your home's unique needs, soil conditions, and budget.

Common Underpinning Methods

underpinning basement options

  Associated Custom Services  

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  • Structural Beams: Installation of new steel beams and posts to replace existing supports or to remove load-bearing walls for an open-concept design.

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  • Basement Walkout: Excavating and building a separate entrance (walkout) for better access, light, and potential rental unit requirements.

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  • Egress Windows: Enlarging windows or installing new ones to meet fire code requirements for basement bedrooms.

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  • Radiant Floor Heating: Incorporating a system of pipes/cables into the new concrete slab for highly efficient heating.

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  • Water Service Upgrade: Upgrading older, smaller diameter water lines (e.g., ½-inch to ¾-inch copper) for better water pressure in the home.

💰 Cost & Financial Considerations

Underpinning is a significant investment. Costs vary widely based on complexity, depth, and the linear footage of your foundation.

Typical Toronto Cost Range

underpinning cost

 IMPORTANT:  Cost per linear foot typically only covers the sequential digging, rebar, and concrete for the new footings. It generally does not include engineering, waterproofing, new drains/plumbing, or the new concrete floor slab. Always ask for a fully itemized quote.

 Key Cost Factors 

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  • Depth of Lowering: Deeper excavation requires more labour and soil removal, increasing the cost.

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  • Soil Conditions: Unstable, clay, or contaminated soil will require more expensive engineering oversight and disposal.

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  • Accessibility: Limited access to the basement (e.g., narrow stairs, small exterior access) increases labor time and cost for soil removal.

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  • Adjacent Structures: If your home is very close to a neighbour's, special engineering and shoring may be required to protect their foundation.

⚖️ Building Code & Regulations

The City of Toronto and the Ontario Building Code (OBC) have strict rules for foundation work.

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  • Engineer Involvement is Critical: A Professional Engineer is legally required to design and supervise the work if:

    • The underpinning is constructed below the footing of an adjacent building and within the "angle of repose" of the soil.

    • The underpinning exceeds 1200 mm (4 feet) of laterally unsupported height.

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  • Required Inspections: City of Toronto inspectors must review the work at several stages to ensure compliance with the approved engineered plans.

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  • Protection of Neighbouring Property: You are responsible for protecting the stability of adjacent properties. This is a primary reason for mandatory engineering oversight and permits.

Backed by over 25 years of experience and comprehensive insurance, our team delivers exceptional quality. Book your Free  Consultation Now

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