BASEMENT Lowering TORONTO

Before any physical work begins, every basement underpinning project in Toronto starts with a detailed engineering design and permit application. A licensed structural engineer visits the property to assess the existing foundation, measure the current ceiling height, and evaluate soil and load-bearing conditions. Based on this inspection, the engineer prepares structural drawings that outline the underpinning method, concrete thickness, rebar reinforcement, and excavation sequence.

Once the design is complete, these drawings are submitted to the City of Toronto Building Department for review. The city issues a building permit only after confirming that the project meets all requirements under the Ontario Building Code and local zoning bylaws.

This stage ensures that the underpinning process is both structurally safe and legally compliant, providing homeowners with a clear, approved plan before excavation begins. At Strong Basements Inc., we manage the full engineering and permitting process, from site measurements to permit acquisition, so our clients can start their project with confidence and peace of mind.

Before any excavation begins, we evaluate the property layout, basement access, and site conditions to plan the safest and most efficient way to complete the project. Every basement is different, so our team designs a custom work plan for each site. This includes determining where to install the conveyor belt system for soil removal, how to position disposal bins for easy pickup, and where to locate concrete trucks and pumps for smooth material delivery.

Once the logistics are set, we prepare the basement interior by removing all finishes, partitions, and debris to create a clear workspace. We seal off doorways, stairwells, and vents to keep dust from spreading into the rest of the house.

We also ensure that the homeowner can continue living upstairs during construction. To achieve this, we suspend the HVAC system and water heater on secure straps, maintaining heating, hot water, and ventilation throughout the process.

By planning every step in advance and adjusting the property setup for efficiency and safety, Strong Basements Inc. ensures that the underpinning project runs smoothly, cleanly, and with minimal disruption to daily life.

At Strong Basements Inc., we perform underpinning in a controlled, step-by-step process to keep the structure stable during every phase of construction. Unlike many contractors who excavate the entire basement at once, we complete the full excavation only after the final underpinning stage. This approach ensures the foundation remains supported and secure at all times.

The process begins with the excavation of the first underpinning section to the designed depth, plus eight additional inches for the gravel base and new concrete floor. Once the soil is removed, the bottom of the original footing is cleaned to expose a solid surface for the new footing.

Next, a structural engineer performs an inspection and confirms that the conditions meet the design requirements. The engineer provides a structural report, which is submitted to the City of Toronto building inspector for review and approval before the work continues.

After inspection, we install wooden concrete forms according to the underpinning method specified in the engineering drawings. Depending on the project, this may include the non-shrink type, overpour type, or flush-with-wall (L-shape) type.

We then pour the concrete into the forms and allow it to cure for 24 to 48 hours. Once hardened, non-shrink grout is applied where needed to seal the joint between the new and existing foundation.

The same procedure is repeated for the second and third underpinning stages, with each section excavated, inspected, formed, and poured in sequence. This method ensures the building remains stable, the foundation is reinforced, and the basement lowering process is completed safely and accurately.

Before moving on to the next phase of basement lowering, which is the Water Management System, we complete all additional structural upgrades required by the engineering design. Every home is unique, and depending on the project, some basements may require reinforcement or modification beyond standard underpinning.

This can include the installation of new load-bearing posts, I-beams, or LVL beams to replace aging supports or to redistribute the weight of the structure after changes to the foundation layout. In some projects, we also remove portions of the foundation wall to create basement extensions, open-concept layouts, or walkout access points.

Each structural task is completed strictly according to the engineered drawings and specifications. Before advancing to the next stage, our team ensures that all supports, reinforcements, and beam connections are properly installed, aligned, and inspected for stability.

By finalizing these structural elements first, Strong Basements Inc. ensures that the building’s load paths remain secure, creating a solid and reliable base for the upcoming basement waterproofing and drainage system installation.

Interior basement waterproofing is a mandatory part of every basement lowering project. When the basement floor is lowered, it goes below the level of the existing exterior weeping tile system. Without a new waterproofing setup, the lower section of the foundation would be exposed to groundwater and hydrostatic pressure, increasing the risk of leaks or moisture damage.

To prevent this, we first adjust the existing storm drainage system and connect it to a new interior weeping tile system. This allows both systems to work together, helping the old exterior drains continue removing water efficiently while balancing underground pressure.

We then install a waterproofing membrane on the interior side of all basement walls. The membrane covers the foundation surface from the top of the wall down to the bottom of each underpinning section. Its purpose is to stop any moisture that seeps through the construction joint between the original footing and the new underpinning, directing it downward instead of allowing it to enter the basement.

Next, we lay a 4-inch perforated weeping tile pipe around the entire interior perimeter. This pipe collects groundwater and directs it toward the sump basin. A sump pump system is then installed to automatically pump the collected water outside of the building, keeping the basement dry and protected year-round.

At Strong Basements Inc., we treat waterproofing as a structural necessity, not an optional feature. A properly designed and installed interior waterproofing system ensures that the newly lowered basement remains dry, stable, and protected for decades to come.

When the basement layout changes, the drainage system must also be redesigned. The existing plumbing is usually too high for the new lowered floor, so we replace old cast-iron or clay pipes with new PVC or ABS pipes and install rough-ins for all future fixtures such as bathrooms, kitchens, and laundry rooms.

To flood-proof the new basement, we install a backwater valve on the main sanitary line. This device prevents sewage from backing up into the basement during heavy rain or municipal sewer overloads, keeping the space safe and dry.

In some homes, the main drain pipe is not deep enough to allow gravity flow from the new basement fixtures. In these cases, we install a sewage ejector system — a sealed basin with a powerful pump that collects all wastewater from basement utilities (such as toilets, sinks, and laundry) and pumps it upward into the main drain line.

All sanitary drainage work is completed according to Ontario Building Code standards and inspected by city plumbing officials before being covered. By rebuilding the drain system at this stage, Strong Basements Inc. ensures the new basement is ready for reliable plumbing, safe drainage, and future finishing.

In many older Toronto homes, the main water service pipe is outdated and undersized. It is often made of lead or half-inch copper, which limits water pressure and can pose long-term health or maintenance concerns. The main shutoff valve and water meter are usually located on the front wall near the foundation, which can interfere with the new basement layout after lowering.

As part of the basement lowering process, we can upgrade the old ½-inch line to a ¾-inch copper pipe, giving the home better water flow and modern plumbing capacity. This is especially important if the new basement will include additional bathrooms, laundry, or a kitchen.

We also relocate the water meter from the front wall to the new mechanical or furnace room. This makes the plumbing system easier to access, keeps it protected, and aligns it with the updated basement design.

All water line replacements and relocations are completed using City of Toronto-approved materials and methods. Upgrading the main water service during the underpinning project helps avoid future disruptions and ensures the new basement is fully compatible with current plumbing standards.

Once all water management systems — including waterproofing, the new sanitary drain, sump pump, backwater valve, and upgraded water service — are installed, we schedule a City of Toronto plumbing inspection. This step is mandatory before covering or pouring the new concrete floor.

During the inspection, the city plumbing inspector carefully checks that all plumbing work complies with the Ontario Building Code. They review pipe sizes, materials, slopes, venting, and the correct installation of the backwater valve, sump pump, and water service connections. The goal is to ensure the drainage and water systems function properly under real conditions.

One of the key parts of this inspection is the “ball test.” The inspector drops a small test ball into the main stack cleanout, and it must roll smoothly by gravity all the way to the backwater valve at the front of the building. This confirms that the drain pipe slope is correct and that there are no dips or obstructions that could cause blockages.

After the plumbing inspection is passed, the system is officially approved, and the basement is ready for the final phase — gravel bedding, insulation, and the new concrete floor installation.

At Strong Basements Inc., we coordinate all inspections directly with city officials, ensuring every detail meets the required standards and giving homeowners confidence that their new basement systems are safe, efficient, and fully code-compliant.

The basement concrete floor is one of the final and most important stages of the basement lowering process. It creates a stable, dry, and comfortable surface that supports the new living space and protects the foundation from moisture and movement.

We start by installing a 4–5 inch layer of clean gravel across the entire basement floor. The gravel is leveled and compacted with a vibratory plate to achieve full settlement, ensuring a solid base for the new slab. This step helps prevent future sinking or cracking of the floor.

Next, we install a Super Six (6-mil) polyethylene moisture barrier over the compacted gravel. This vapor barrier prevents ground moisture from evaporating into the concrete and the basement interior, helping to keep the space dry.

We then recommend and install 2-inch R10 rigid foam insulation across the entire floor. This layer provides a thermal break between the concrete and the cold soil, making the basement more energy efficient and comfortable to walk on.

After that, we lay steel welded wire mesh over the insulation to reinforce the slab and minimize cracking from natural movement or temperature changes. If requested, this is also the stage where we install radiant in-floor heating pipes, allowing homeowners to enjoy efficient and evenly distributed warmth throughout the basement.

Finally, we pour a 32 MPa concrete mix, which offers superior strength and durability. The concrete is carefully leveled, troweled, and power-finished for a smooth surface that can be left polished or used as a base for flooring such as vinyl, tile, or laminate.

At Strong Basements Inc., every concrete floor is built to last, providing both structural stability and comfort for the newly lowered basement.

The final inspection marks the official completion of the basement underpinning and lowering project. At this stage, a licensed structural engineer performs a detailed review of all work completed throughout the project. The engineer compares every structural element — such as the underpinning sections, concrete strength, reinforcement, waterproofing, and drainage installations — against the approved engineering drawings and the Ontario Building Code requirements.

During this inspection, the engineer ensures that the foundation reinforcement, floor structure, and plumbing systems were built exactly as designed, with all materials and methods meeting safety and durability standards. This evaluation confirms that the house remains fully supported, stable, and compliant with all building regulations.

After the inspection, the engineer prepares a final structural report that documents the results and verifies that all construction stages meet the approved plans. This report is then submitted to the City of Toronto Building Inspector, allowing the city to officially close the building permit and mark the project as completed and code-compliant.

By completing this final step, Strong Basements Inc. ensures the homeowner receives full documentation of the finished work, giving confidence that the new basement is structurally sound, inspected, and ready for use or finishing.