In Toronto’s competitive real estate market, every square foot of living space comes at a premium. With the average detached home price in the GTA hovering well above the million-dollar mark, many homeowners are looking for ways to maximize their existing property rather than upgrading to a larger home. This economic reality has made basement lowering—particularly underpinning—increasingly popular throughout Toronto and the surrounding areas.

Many Toronto homes, especially those built before the 1960s, were constructed with basements that were never intended to be living spaces. These basements typically have ceiling heights of 5-6 feet, making them unsuitable for comfortable habitation and non-compliant with current building codes for living areas. Underpinning allows homeowners to transform these cramped, unused spaces into valuable living areas without the enormous expense of moving to a larger home.

If you’re considering digging out your basement, this guide will walk you through everything you need to know about the process, from initial planning to project completion.

Understanding Your Options: Underpinning vs. Bench Footing

Before diving into the underpinning process, it’s important to understand the two main approaches to basement lowering:

Underpinning

Underpinning involves excavating beneath your existing foundation in sections and extending the foundation walls downward to create greater ceiling height. This method provides full height across the entire basement and maximizes your usable square footage.

Advantages of Underpinning:

• Maximizes usable floor space
• Typically adds greater value to your property
• Provides consistent ceiling height throughout
• Creates a more aesthetically pleasing finished space
• Better long-term investment

Bench Footing

Bench footing (or benching) creates a concrete “bench” or ledge around the perimeter of your basement where the original foundation meets the new lower floor. The central area is excavated deeper while the foundation walls remain untouched.

Advantages of Bench Footing:

• Generally less expensive than underpinning
• Typically requires less time to complete
• Often involves fewer engineering complexities
• May not require reinforcing existing foundation walls
• Can be suitable for homes where structural considerations limit underpinning options

While bench footing is a valid alternative in some situations, this article will focus primarily on the underpinning process, as it’s the preferred method for most Toronto homeowners seeking to maximize their basement’s potential.

The Underpinning Process: What to Expect

1. Initial Assessment and Planning (2-4 Weeks)

The first step in any basement underpinning project is thorough assessment and planning:

• Structural Engineer Evaluation: A qualified structural engineer will examine your foundation, soil conditions, and overall structural integrity to determine if underpinning is feasible.
• Architectural Drawings: Detailed plans will be created showing the existing structure and proposed modifications.
• Permit Applications: Your basement lowering contractor will help prepare and submit building permit applications to the City of Toronto. This typically includes structural drawings, site plans, and sometimes soil reports.
• Utility Locates: Before any excavation begins, all underground utilities must be precisely located to avoid disruption or damage.

During this phase, your contractor should also discuss waterproofing strategies, as Toronto’s climate makes proper moisture management essential for any basement project.

2. Preparation and Setup (1 Week)

Once permits are approved, the preparation phase begins:

• Site Protection: Contractors will protect your home’s interior by sealing off the basement from living areas, typically using plastic sheeting and temporary walls to control dust.
• Utility Disconnection/Relocation: Some utilities may need temporary disconnection or rerouting, particularly drainage systems that will be modified during the project.
• Equipment Setup: Access points will be created for removing excavated soil, and necessary equipment will be brought on site.
• Structural Support: Temporary support systems will be installed to ensure the house remains structurally sound during excavation.

3. The Underpinning Process (4-8 Weeks)

This is the core phase of the project, where the actual digging and foundation extension occurs:

• Segmented Excavation: Rather than digging out the entire basement at once (which would compromise structural integrity), underpinning proceeds in small sections—typically 3-4 feet wide—working around the perimeter in a carefully planned sequence.
• Pin Installation: In each section, contractors dig below the existing foundation to the desired depth (typically 1-3 feet deeper than the current basement).
• Forming and Pouring: Concrete forms are created in each excavated section, and new concrete is poured to extend the foundation wall downward.
• Curing Time: Each section must adequately cure before adjacent sections are excavated, creating a methodical, step-by-step process around the basement.
• Central Excavation: Once the perimeter is complete, the central area of the basement can be excavated to the new depth.

This methodical approach ensures your home remains structurally sound throughout the process. A typical 1,000 square foot basement might be divided into 30-40 sections, each requiring 1-2 days to complete.

4. New Floor Installation (1-2 Weeks)

With the foundation walls extended and the central area excavated:

• Drainage System: A proper drainage system is installed, typically including weeping tiles that direct water to a sump pump.
• Gravel Base: A layer of gravel is spread to provide drainage underneath the new floor.
• Vapor Barrier: A polyethylene membrane is installed to prevent moisture from rising through the concrete.
• Concrete Floor: A new concrete floor is poured to create a smooth, level surface.
• Waterproofing: Additional waterproofing measures may be applied, particularly important in Toronto’s climate where freeze-thaw cycles can exacerbate water issues.

5. Finishing Work (Timeframe Varies)

The final phase transforms your newly excavated space into a livable area:

• Framing and Insulation: Walls are framed and properly insulated to meet building code requirements.
• Electrical and Plumbing: New electrical systems and plumbing are installed as needed.
• Drywall and Finishes: Walls and ceilings are completed with drywall, paint, and trim.
• Flooring: Appropriate flooring is installed based on your design preferences.

The finishing phase timeframe varies dramatically based on the level of finishing desired, from a simple, utilitarian space to a fully-equipped basement apartment.

Critical Considerations for Toronto Homeowners

Building Permits and Regulations

The City of Toronto strictly regulates structural modifications like basement underpinning. Required permits typically include:

• Building Permit
• Plumbing Permit (if applicable)
• Electrical Permit (if applicable)

Toronto’s building code also stipulates minimum ceiling heights for habitable spaces—generally 6’5″ (1.95m) for at least 75% of the basement area. Your basement lowering contractor should be intimately familiar with these requirements and handle the permit process for you.

Soil and Water Considerations in the GTA

Toronto’s geography presents specific challenges for basement underpinning:

• Clay Soil: Many Toronto neighborhoods have clay-heavy soil, which retains water and can exert significant pressure on foundation walls.
• High Water Table: Areas closer to Lake Ontario often have higher water tables, requiring robust waterproofing systems.
• Freeze-Thaw Cycles: Toronto’s seasonal temperature variations can cause soil expansion and contraction, potentially affecting foundation stability.

These factors make proper waterproofing essential for any basement lowering project in the GTA. A quality basement lowering contractor will address these issues proactively with appropriate drainage systems and waterproofing methods.

Choosing a Qualified Basement Lowering Contractor

Given the structural significance of underpinning, selecting a qualified contractor is perhaps the most important decision you’ll make. Look for:

• Extensive experience specifically with basement underpinning in Toronto
• Proper licensing and insurance
• Knowledge of local building codes and soil conditions
• Strong references from previous underpinning clients
• Willingness to provide detailed contracts and timelines
• In-house engineering expertise or established relationships with structural engineers

Living Arrangements During Construction

Most homeowners wonder if they can remain in their home during basement underpinning. While it is possible to live in your home during the process, you should expect:

• Significant noise during working hours
• Some dust despite containment efforts
• Limited access to certain utilities at specific points
• Workers present in your home for 6-10 weeks
• Potential vibration that might affect sensitive items

Some families choose to temporarily relocate during the most intensive phases of the project, particularly if they have young children, work from home, or have health concerns related to dust or noise.

The Return on Investment: Is Underpinning Worth It?

For most Toronto homeowners, basement underpinning represents a significant investment—typically $50,000 to $80,000 for the structural work alone, with finishing costs potentially adding another $25,000 to $50,000 depending on quality and features.

However, when evaluated against Toronto’s real estate prices, the math often favors underpinning:

• Added Living Space: Converting an unusable 5-foot basement to a fully functional 7.5-foot living area might add 800-1,000 square feet of living space to your home.
• Property Value Increase: While return on investment varies by neighborhood, finished basement space typically increases property value by $200-$300 per square foot in desirable Toronto neighborhoods.
• Income Potential: A properly permitted basement apartment can generate rental income of $1,500-$2,500 monthly in many Toronto neighborhoods.
• Comparison to Moving Costs: When factoring in real estate commissions, land transfer taxes, moving expenses, and the price difference for a larger home, underpinning often represents a more economical solution to gaining additional space.

For many Toronto families, underpinning offers the ability to remain in their preferred neighborhood while gaining the space they need—a compelling combination in the city’s competitive real estate market.

Planning for Success

Basement underpinning is a complex but rewarding project that can dramatically increase your usable living space and property value. By understanding the process, preparing adequately, and working with qualified professionals, you can ensure a successful transformation of your Toronto home’s basement.

The key to a positive underpinning experience lies in thorough planning, realistic expectations, and selecting an experienced basement lowering contractor with a proven track record in the GTA. When properly executed, underpinning can provide your family with valuable additional living space for decades to come, making it one of the most significant and worthwhile investments you can make in your Toronto home.

There are several solutions to a wet basement such as excavating around the home’s perimeter as well as installing drains along the inside of basement walls. For more information and advice on Underpinning your basement  please feel free to contact our team of foundation-repair professionals at Nusite Contractors for a free inspection and written estimate. Our work is fully certified, insured, and guaranteed as well as made to last.  We serve Toronto and the surrounding GTA.