When you ask a Toronto contractor about basement lowering, you will likely be quoted two options: bench footings and full underpinning. The price difference can be $20,000 to $40,000. The right choice depends on what you plan to do with the space - and getting it wrong means either overpaying or ending up with a basement that does not meet your goals. This post compares both methods clearly so you can make an informed decision.
What Are Bench Footings?
A new concrete footing is poured inside the existing foundation wall at the new, lower floor level. The existing wall stays in place - the new footing creates a "step" or "bench" on the inner perimeter. The result: the floor level drops in the center, but a bench, or ledge, 12 to 24 inches wide runs along the perimeter walls at the old floor level.
Structurally, the bench transfers the load from the existing footing to the new lower floor level without digging below the old footing.
What Is Full Underpinning?
The foundation wall is extended downward by excavating beneath the existing footing and pouring new concrete below it, done in staged 3 to 4 foot bays sequentially around the perimeter. The result: the full floor area at the new lower level is available - no bench, no lost floor space.
Structurally, the new mass of concrete extends the foundation depth, moving the load-bearing point lower.
Side-by-Side Comparison
| Bench Footings | Full Underpinning | |
|---|---|---|
| Cost per linear foot | $250-$350 | $350-$600 |
| Typical total cost | $20,000-$40,000 | $45,000-$90,000 |
| Floor area preserved | No - loses 12-24" per wall | Yes - full footprint |
| Headroom gained | Yes (center of basement) | Yes (full floor) |
| Best for | Storage, gym, laundry | Legal suite, finished living space |
| Permit required | Yes | Yes |
| Engineer required | Yes | Yes |
| Timeline | 4-6 weeks | 8-16 weeks |
| Eligible for legal suite (OBC) | Depends on room size math | Yes |
When Bench Footings Are the Right Choice
- Budget is the primary constraint and the space will be non-habitable - storage, utilities, laundry
- A gym or workshop where you spend time in the center, not against the walls
- The existing basement is wide enough that losing 12-24 inches per benched wall still leaves adequate usable space
- You do not intend to rent the space or create a legal suite
- Headroom in the center is the priority - e.g., 5'10" to 7'4" in the middle is enough
When Full Underpinning Is the Right Choice
- You plan to create a legal basement suite - OBC minimum room sizes are non-negotiable and bench footings lose floor area
- You want a finished basement with a full-width layout - bedroom, open living, kitchen - where floor area matters
- Your basement is narrow, under 20 ft wide: losing 24 inches to bench footings on each side reduces the usable center to under 15 ft, too narrow for a comfortable suite
- Structural issues need to be addressed simultaneously - underpinning can also reinforce a failing foundation
The OBC Legal Suite Problem with Bench Footings
OBC Part 9 requires a habitable room minimum floor area of 7 sq m (75 sq ft). A 15 ft by 15 ft basement center - after bench loss on two walls in a 20 ft wide home - works out to 225 sq ft open plan, which might still work for a bachelor unit. But add a bedroom (75 sq ft minimum), kitchen, bathroom, and laundry, and the floor area math gets very tight.
A structural engineer and architect should review the bench footing layout against OBC room sizes before committing to this method for a legal suite project.
Can You Mix Bench Footings and Full Underpinning?
Yes - it's common on projects where one or two walls have limited access or do not need the full depth. Example: underpin three sides for full floor, bench footing the fourth wall where a shared party wall limits excavation depth. The engineer specifies which method to use on each wall section in the stamped drawings.
What If You Choose the Wrong Method?
Choosing bench footings when you needed full underpinning means you will not have enough floor area for your intended use. There is no practical way to convert bench footings to full underpinning after the fact without tearing out the bench and starting that portion over.
This is why the decision must be made correctly before construction starts - not after a quote comes in cheaper.
How BaseWorks Recommends the Right Method
Our structural engineer assesses your specific basement - floor area, width, ceiling goal, and intended use - before recommending a method. We will not recommend bench footings for a legal suite project where floor area is borderline; the risk to the homeowner is not worth the cost saving.
A Worked Example: A Typical Toronto Semi
An example makes the trade-off easier to see. Imagine a semi-detached house with a basement about 18 feet wide and 40 feet long, with a party wall on one side. The owner wants to lower the floor about a foot to improve headroom.
With bench footings on the two long walls, the centre of the basement is lowered but a ledge remains along each side. The usable width of the lowered floor shrinks by the width of the two benches, so a basement that was 18 feet wide now has a lowered floor noticeably narrower than that. For storage or a gym, that is acceptable. For a bedroom, living area and kitchen, the narrower floor starts to limit the layout.
With full underpinning, the lowered floor runs wall to wall, so the full width is available for the layout. The trade-off is cost and time. That is why the method should follow what you intend to do with the space. Our legal basement suite guide shows how to test a layout against the code requirements before choosing.
Questions to Ask Before You Choose
Because the choice is hard to reverse, it is worth asking your engineer and contractor a few direct questions. These help you decide whether a lower price is a real saving or a limit on what you can do.
- What will the usable floor width be after the work? Ask for the number, not just the method.
- Does the layout I want still meet room-size requirements? The engineer or designer should check it against the drawings.
- How does each method affect plumbing and drainage? Floor drains and sump pits are easier to place with a clear floor.
- What are the access conditions? Limited access can make one method more practical than the other.
- Can a hybrid approach work? Some walls may need less than the full treatment.
The answers often make the decision clear. For the full cost picture of both methods, see our basement lowering cost guide.
How the Choice Affects Later Work
The method you choose also shapes what comes after the structural work. A clear, full-width floor is simpler to waterproof and drain, since the perimeter drain and sump can run the full length of the wall. Bench footings add a ledge that has to be integrated into the finishing, whether by framing it as a seat or shelf, boxing it in or building around it.
It also affects how the finished space is used. Furniture, doors, stairs and mechanical equipment all have to fit within the floor that remains, and a bench along a wall changes where cabinets, bathrooms and bedroom doors can sit. If you are planning a finished space, ask the designer to check the layout against the actual benched dimensions. For the process itself, our guide to what happens during a basement lowering explains how each stage unfolds.
Frequently Asked Questions
Sometimes, but only if the remaining floor area after the bench loss still meets OBC minimum room sizes - 7 sq m (75 sq ft) per habitable room. In narrow basements (under 20 ft wide), losing 12-24 inches per wall to a bench often makes the center too tight for a compliant bedroom and living space. A structural engineer should verify the layout math before committing to bench footings for a legal suite project.
Bench footings typically cost $250-$350 per linear foot versus $350-$600 for full underpinning - roughly 25-40% less. For a typical Toronto home this translates to a total project difference of $20,000-$40,000. The savings come from not having to excavate below the existing footing.
Bench footings typically lose 12 to 24 inches of floor width along each benched perimeter wall, depending on the footing depth and soil bearing requirements specified by the engineer. In a home with bench footings on two opposing walls, this can reduce the usable center width by 2 to 4 feet total.
Yes, when properly engineered - both methods, when designed and built to code by a licensed structural engineer, provide adequate structural support for the loads above. The difference is not structural strength but usable floor area: bench footings preserve the existing footing depth and add a stepped ledge, while full underpinning extends the footing deeper for the entire floor area.
Not easily. The bench would have to be removed and that portion redone as full underpinning, which is close to starting that section again. That is why the choice should be made carefully before work begins, based on how you want to use the space.