- You can lower a basement floor two ways: underpinning, which builds new footings under the walls, or a bench footing, which leaves the old footing and pours a step around the inside.
- Bench footings typically cost $20,000 to $45,000, roughly 20 to 40% less per linear foot than underpinning, but take floor space along every benched wall.
- Underpinning typically costs $55,000 to $95,000 for a detached house and keeps the full floor area.
- Either way you need a building permit, usually backed by engineered drawings, and the target height usually comes from the Ontario Building Code.
Why basements need lowering
Plenty of older houses around Hamilton were built with cellars, not basements: low ceilings, a thin or cracked floor, and footings only as deep as they needed to be at the time. To turn that space into a family room, a bedroom or a secondary suite, you need more height, and in an existing house the only direction left is down.
Lowering the floor means breaking out the old slab and digging out soil. Once the new floor goes below the bottom of the existing footings, the walls need new support, or the soil holding them up would be exposed. That's where the two methods split.
Option 1: underpinning
Underpinning carries the foundation walls down to a new, deeper footing. It's dug in small numbered sections in an order an engineer sets, so the house stays supported, and each section is poured before the ones beside it are opened. When it's done, the walls run straight down to the new floor.
- Keeps every square foot of floor space.
- Replaces shallow or tired footings with new ones under the whole wall.
- Costs more and takes longer on site than benching.
- Needs more engineering, especially beside an attached neighbour.
For the full process, permits and costs, read our guide to underpinning a foundation.
Option 2: bench footing
A bench footing leaves the existing footing where it is. The floor is dug down inside the basement, and a concrete bench, a low wall or step, is poured around the inside of the foundation to hold the soil under the old footing in place. The basement gets deeper, but the bench sits along the walls.
- Costs less, typically 20 to 40% below underpinning per linear foot, and less again in total.
- Leaves the original footing undisturbed, which keeps the job simpler and usually shorter.
- Takes floor space. The bench is roughly as wide as the drop is deep, often 12 to 24 inches along each benched wall.
- Limits layout. It can double as a shelf or a seat, but it gets in the way of furniture and framing along the walls.
Underpinning vs bench footing, side by side
| Factor | Underpinning | Bench footing |
|---|---|---|
| Floor space | Keeps the full floor area | Loses a strip along each benched wall, roughly as wide as the drop is deep |
| Existing footing | Replaced by new, deeper footings | Left in place |
| Typical cost per linear foot | $350 to $600 | $250 to $350 |
| Typical total | $55,000 to $95,000 for a detached house, structural work | $20,000 to $45,000 |
| Building permit | Required | Required |
| Engineered drawings | Usually | Usually |
| Best for | Finished living space, secondary suites, getting every bit of room | Tighter budgets, modest drops, rooms where a step along the wall won't matter |
Typical Hamilton-area market ranges before tax, drawn from 2026 Ontario price guides and published contractor rates. Your quote is based on your house.
How much headroom do you need?
The Ontario Building Code sets the minimums, and they're usually the target. For basement space in a house, Table 9.5.3.1 of the 2024 Code calls for 2,100 mm (about 6 feet 11 inches) over at least 75% of the basement area, dropping to 1,950 mm (about 6 feet 5 inches) under beams and ducts.
Building a secondary suite? Since January 1, 2025, the Code sets 1.95 m (about 6 feet 5 inches) for ceilings in a secondary suite, and 1.85 m (about 6 feet 1 inch) under beams and ducting. Those rules are for a second unit in a house, so a third unit has to be checked against other parts of the Code.
Then plan for the finishes. Flooring, the ceiling itself and any new ductwork all eat into the height, so we set the finished ceiling first and work back to how deep the floor has to go.
Planning a bedroom? Unless there's a door on that level straight to the outside, it also needs an egress window: an opening of at least 0.35 m², no dimension under 380 mm, and 550 mm of clear space in front if it opens into a window well.
Drainage, waterproofing and the new floor
Lowering a basement puts the floor closer to the groundwater, so drainage isn't optional. The Building Code calls for drainage at the bottom of exterior foundation walls unless it can be shown to be unnecessary: drain pipe at least 100 mm in diameter, covered by at least 150 mm of crushed stone, carried to a sewer, a ditch or a dry well. Where gravity drainage isn't practical, that means a sump pump.
The new slab goes down over a compacted stone base, and it's the best time to add weeping tile under it, a sump pit, and waterproofing on the walls while they're bare. Doing any of that later means breaking up a brand-new floor.
If the old weeping tile was tied into the sanitary sewer, lowering is also the moment to disconnect it. In Burlington, Oakville and Milton, Halton Region covers disconnecting weeping tile and adding a sump pump at 100%, up to $6,500.
What it costs to lower a basement
Typical Hamilton-area ranges for the structural side of the job:
| Scope | Typical range |
|---|---|
| Bench footing, per linear foot | $250 to $350 per linear foot |
| Bench footing, typical basement | $20,000 to $45,000 |
| Underpinning, per linear foot | $350 to $600 per linear foot |
| Underpinning, detached house | $55,000 to $95,000 |
| Underpinning with waterproofing, drains and a new slab | $70,000 to $120,000 |
| New basement floor on its own | $8,000 to $20,000 |
Typical market ranges before tax, drawn from 2026 Ontario price guides and published contractor rates.
On top of that come engineered drawings, typically $1,500 to $5,000, and whatever finishing you have planned. A lowered floor is also the cheapest moment to add weeping tile, a sump and waterproofing, because everything is already open.
Which one is right for your house?
- Choose underpinning if you want every bit of floor space, you're building a secondary suite, or the existing footings are shallow, cracked or sitting on poor soil.
- Choose a bench footing if the budget is tight, you only need a modest drop, and a step along the walls won't get in the way of how you'll use the room.
- Look at the walls first if they're bowing, crumbling or badly cracked. Neither method fixes a failing wall on its own, and a section may need to be rebuilt.
We'll lay out both options in writing after an assessment, with the floor area you'd keep or lose and the price of each, so you can decide with real numbers.
Permits, drawings and how the job runs
Both methods change how a house is supported, so both need a building permit and are usually designed from stamped structural drawings. Ontario's Building Code Act requires a permit for any material alteration of a building, and Oakville and Mississauga list both excavating to increase existing headroom and underpinning foundation walls as permit work.
The usual order is an assessment and soil check, engineered drawings, the permit, then excavation of the floor and either the underpinning sections or the bench, followed by new drainage, the slab, inspections and sign-off. Expect several weeks on site, with underpinning usually running longer than a bench.
Basement lowering questions
How much does it cost to lower a basement floor?
How much floor space does a bench footing take?
Can I lower my basement floor without underpinning?
Do I need a permit to lower my basement?
Can we stay in the house while the basement is lowered?
Basement lowering with AVH
Related guides
AVH Foundations works across Hamilton, Burlington, Oakville, Milton, Ancaster, Dundas, Stoney Creek, Waterdown, Cambridge, Brantford, Caledonia and Grimsby.