Did you know that basement underpinning can increase your home’s value by up to 25% while also reinforcing its structural integrity? If you’ve noticed cracks in your foundation, uneven floors, or doors that won’t close properly, you might need underpinning to strengthen and stabilize your basement.
In this guide, we’ll cover everything you need to know about basement underpinning, including what it is, why it’s needed, and how the process works—especially if you own a home in Toronto’s shifting soil conditions.
As a contracting group specializing in basement underpinning in Toronto, we often get asked this simple question, “what is underpinning?” Below is a brief answer to that question.
“Underpinning” is an industry term that’s generally used to describe reinforcing an existing foundation. This may be to shore-up a structure that was poorly built originally or has degraded over time, is subject to subsidence or land-slippage, or is being prepared to carry extra weight. Underpinning is also performed when a homeowner wants to have their basement foundation dug out to increase the ceiling height of their basement. This is also known as basement lowering.
What Is Basement Underpinning?
Basement underpinning is the process of reinforcing and deepening your home’s foundation. This is done by extending the foundation deeper into the ground or strengthening existing supports. The process is commonly used for:
- Fixing foundation issues caused by soil movement, water damage, or poor construction.
- Increasing basement height to create livable space, such as a finished basement.
- Improving home value by adding square footage and reinforcing structural integrity.
Why Do Homes Need Underpinning?
If you’re unsure whether your home needs underpinning, here are some common warning signs:
✅ Visible cracks in basement walls or floors
✅ Uneven floors or sinking sections of the house
✅ Doors and windows that stick or won’t close properly
✅ Gaps forming between walls and ceilings
✅ Moisture or water leaks in the basement
These issues often occur due to Toronto’s freeze-thaw cycle, which causes soil expansion and contraction, leading to foundation shifts over time.
Different Methods of Basement Underpinning
Not all homes require the same type of underpinning. The method used depends on factors like soil conditions, foundation structure, and the extent of foundation damage. Here are the four primary basement underpinning methods:
1. Mass Concrete Underpinning (Traditional Method)
🔹 Best for: Older homes with simple foundation structures.
🔹 Process: This method involves excavating small sections beneath the foundation in a phased approach and filling them with concrete. The new concrete reinforces the existing foundation, making it stronger and more stable.
🔹 Advantages:
✅ Cost-effective for minor foundation adjustments.
✅ Minimal disruption compared to other methods.
✅ Suitable for shallow foundations.
🔹 Disadvantages:
❌ Not ideal for homes with deep foundations or poor soil conditions.
2. Beam and Base Underpinning
🔹 Best for: Homes with uneven weight distribution or structural weaknesses in load-bearing walls.
🔹 Process: This method uses reinforced concrete beams to transfer the weight of the structure onto a newly built base below the existing foundation. The base provides additional stability while minimizing movement in weak soil.
🔹 Advantages:
✅ Provides superior structural reinforcement.
✅ Can be used in conjunction with mass concrete underpinning for extra stability.
🔹 Disadvantages:
❌ More complex and expensive than mass concrete underpinning.
❌ Requires detailed engineering calculations to ensure proper weight distribution.
3. Pile Underpinning
🔹 Best for: Homes with unstable soil conditions, deep foundations, or significant structural issues.
🔹 Process: Piles (either concrete, steel, or helical screws) are driven deep into the ground to reach stable soil layers. The building’s weight is then transferred onto these piles, preventing future settlement.
🔹 Advantages:
✅ Ideal for homes built on weak or shifting soil.
✅ Suitable for deep foundations or structures with heavy loads.
✅ Can be used in high-water table areas where other methods fail.
🔹 Disadvantages:
❌ More expensive due to specialized equipment and labor.
❌ Requires professional engineering assessment before installation.
4. Bench Footing (Alternative to Underpinning)
🔹 Best for: Homeowners who want to increase basement height without excavating beneath the foundation.
🔹 Process: Instead of digging under the foundation, concrete “benches” are built inside the basement along the perimeter walls. These benches provide additional structural support while allowing the basement floor to be lowered within the existing foundation walls.
🔹 Advantages:
✅ More affordable than traditional underpinning.
✅ Does not disturb the existing foundation, reducing structural risks.
✅ Faster construction process compared to other underpinning methods.
🔹 Disadvantages:
❌ Reduces usable floor space due to the concrete bench encroaching into the room.
❌ May not be as effective for homes with serious foundation issues.
Stages in the Process
If there was a single basement job not recommended for amateurs or the uninsured), then basement underpinning has to be the one. Get it right, and you’ll add significant value to your home. Get it wrong though, and you could end up damaging the fabric of your house.
Appoint a licensed structural engineer with a record of completed jobs, to prepare statutory documents and obtain approval for the job.
Appoint a basement-underpinning contractor who’s similarly experienced to complete the following work:
- Remove a small section of the existing foundation to obtain access underground, and replace it with a load-bearing joist.
- Excavate alternate strips to the required depth, and pour shuttered reinforced concrete beneath the exposed sections of foundation.
- When the new foundations are completely cured, complete the balance of the basement underpinning.
- Lay a new floor when everything is stable, and build out the interior of the extended space.
Cost-Benefit Analysis
Houses are valued in terms of living space. A new basement could therefore increase the value of your home by up to 10% – and you get more living space too. Basements are especially popular when it comes to extending homes, because they retain existing footprints, and seldom affect the neighbors.
However, you are effectively building your house “upside down” by adding the walls and floor when the roof’s up already. While the job’s in process the structural integrity of the entire building is compromised in the short-run. If it fails, then your new basement could end up costing you a whole lot more than it’s worth.
Is Basement Underpinning Worth It?
If you’re planning to finish your basement, improve your home’s structural stability, or increase its value, underpinning is a worthwhile investment. Not only does it expand your home’s living space, but it also ensures your foundation is safe and stable for years to come.
Get a Professional Assessment
If you’ve noticed signs of foundation issues, don’t wait! Contact Nusite Group today for a free consultation and expert advice on the best underpinning solution for your home.