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.
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.