Start with the height you have
Measure from the basement floor to the underside of the joists, above any drywall. Then measure again under a duct, because that is the number that decides how the room feels.
Under about 6 feet 6 inches the space will feel like a basement no matter what you spend on it, and it starts to read as a room somewhere around 7 feet. Eight feet is the height at which it reads as part of the house.
Most Toronto houses built before the sixties give you somewhere between 6 and 7 feet. That gap is the reason anyone underpins.
What underpinning is
The footing under your foundation wall sits at a certain depth. Underpinning goes below it, in short sections, and extends the wall and the footing downward. You dig out a metre or so of the basement floor, and the walls follow the floor down.
It is done in sequence, never all at once. A crew excavates and pours one section, lets it cure, then moves along the wall. The order and the widths matter, because at any moment part of your house is being held up by the sections either side of the one that is open.
That is why this is not a job for a general handyman with a bobcat. It needs an engineer's drawings, a permit, and a crew that does this specific work, because the failures are structural, not cosmetic.
Benching, the cheaper alternative
Benching leaves the footing where it is and builds an angled concrete shoulder inward from the base of the wall, then drops the floor in the middle.
You get the ceiling height in the middle of the room. What you lose is floor area around the perimeter, and the bench itself is a permanent concrete ramp along your walls that you have to design around.
Benching is meaningfully cheaper and faster than underpinning, and it carries less engineering risk, though it is still permitted and engineered work. In a wide basement where the perimeter is not precious, it is often the right answer, and it is not always offered. Ask for both prices.
What it costs
Underpinning in Toronto is generally quoted by the linear foot of wall. The rate moves with access, soil, how deep you are going and what is in the way, so the figure is a range rather than a number. Most residential jobs land somewhere between two and five hundred dollars a linear foot, and a typical semi-detached perimeter is a lot of linear feet.
For a whole basement, expect the underpinning alone to be a five-figure number well into the middle of that range, before you have a finished room. Then add the things that always come with it: a new floor slab, new drainage and a sump, waterproofing while the walls are exposed, and usually the electrical and plumbing rough-in.
Benching commonly comes in well under that, and the saving is mostly in engineering, sequencing and time.
Neither number includes finishing the basement. That is a separate project, and it is the one people budget for and then discover they cannot start.
Do it while the walls are open, or do not do it at all
If you are underpinning, everything that belongs against or under that wall gets done now.
Interior weeping tile and a proper sump. Exterior waterproofing if you are excavating outside anyway. A new slab poured over vapour barrier and rigid insulation rather than straight onto soil. Plumbing rough-in for the bathroom you might want in three years, laid now while the floor is open.
Coming back later to do any one of these means opening what you just closed. The extra cost during the dig is small, and afterwards it is the whole job again.
The test for whether you should
Underpinning pays for itself in two situations, and neither of them is "we wanted a nicer basement".
The first is when the extra height creates usable space in a house that has run out of it. A family that needs a fourth bedroom and cannot afford to move is a good candidate.
The second is a legal secondary suite. A basement apartment has to meet minimum ceiling height, egress, fire separation and a set of other requirements before anyone will call it legal. Markham's secondary suite guide puts the height at 1.95 metres in the rooms and 1.85 under beams and ducts, so a basement with 6 feet 6 inches may already clear it. Where it does not, lowering the floor is the only way to get there.
Outside those two, look hard at benching, and look harder at whether the money would do more upstairs.
How long
An engineered drawing set and a permit runs a few weeks to a couple of months depending on the municipality. The underpinning itself, for a typical Toronto house, is usually several weeks of sequenced work, and it does not compress, because the sequence is what keeps the house standing.
Then the basement is a shell, and finishing it runs like any other renovation of that size. Plan on a season for the structural work alone, before the finishing starts.
Send us your two ceiling measurements, one in the clear and one under the lowest duct, and a photo of the stairs. We will tell you whether the height is worth chasing, and whether benching would get you there. Start a conversation.