Underpinning rebuilds the foundation underneath your house a few feet at a time, so the floor can go down and the walls stay exactly where they are. It is the only method that buys headroom and keeps the full floor area — and because it is structural work, it starts with a stamped drawing and a City permit, not a shovel.
Almost every job we look at comes down to one of these. They are not the same job, and they do not need the same amount of depth.
A 1960s side-split in Cooksville or a bungalow in Lakeview commonly measures between six and a half and seven feet from slab to joist, and the ducts and beams take a few more inches out of that. There is no other way to change that number: the joists cannot move and the house cannot be raised. The floor has to come down.
A building permit on its own does not make a basement apartment legal in Mississauga. The unit has to be registered with the City afterwards, and the registration asks for a copy of the permit signed off by every inspector involved. Ceiling height is one of the first requirements a low basement fails.
An addition means setbacks, a larger footprint, a new roof and new exterior walls. Lowering the basement adds finished floor area inside the walls that are already standing and already paid for, and nothing about the outside of the house changes.
The wall is never undermined along its length. It is opened in short, separated pieces, one round at a time, and each piece is filled with concrete before its neighbours are touched.
Usually three to four feet wide, numbered on the drawing before anyone picks up a shovel.
A section is excavated while the ground on both sides of it is still completely undisturbed. The existing footing simply spans the gap.
Formed, reinforced where the drawings call for it, and filled with concrete to just under the old footing. The last inch or two is dry-packed and rammed tight so the new pin actually picks up the load.
This is the honest reason underpinning is measured in weeks rather than days. Anyone offering to open a whole wall at once is describing a different job than the one on the drawings.
Both get the floor lower. They differ in what happens under the existing footing — and in how much of the finished room you are left standing on.
| Underpinning | Bench footing | |
|---|---|---|
| Work below the existing footing | Yes | None |
| Floor area you keep | All of it | Less a strip around the perimeter |
| Relative cost | Higher | Lower |
| Relative time on site | Longer | Shorter |
| Finished wall | Flat, floor to ceiling | A permanent angled ledge |
| Where it wins | Narrow rooms, second units, anywhere the perimeter is usable space | Wide basements, tighter budgets, rooms where a ledge is no loss |
Lowering a basement rarely arrives on its own. These are the pieces that usually come with it.
A door of its own, cut through the wall and out to grade.
See how it works
We do not publish a per-foot number, because the four things below can change it as much as the length of the wall does. A quote that arrives before anyone has measured your basement is a guess.
How the soil gets out and the concrete gets in. A back yard a machine can reach is a different job from a semi where every barrow goes out the front door. Usually the largest single swing.
Every extra foot is more excavation, more concrete and more spoil leaving the property.
One room under a rear addition is not the same job as the full footprint of a bungalow.
Poured concrete, block and older rubble walls each need different handling, and wet ground changes the staging.
Eight stages, in this order, on every underpinning job. The order is not negotiable — the permit, the inspections and the curing time are all tied to it.
Slab to joist in several places, the wall type, where the services sit, and how material could get in and out of the house.
Before drawings and before quotes. Sometimes the depth you want is not available, and that is much cheaper to hear now.
Section widths and their order, the new bearing depth, reinforcement, and the lintel over any new opening.
The application goes to the City with the drawings. Who submits it and who books inspections is agreed in writing first.
Dust separation, a protected route through the house, services capped or moved, then the old slab comes out.
Dug, formed, poured in numbered order, with curing time between rounds. The longest stage, and it cannot be compressed.
Weeping tile at the new footing level into a sump pit, clear stone, vapour barrier, then the concrete.
City inspections at the stages the permit calls for, and a bare, level, drained floor handed back ready for framing.
Four things worth understanding first. No sales pitch in them — they are the questions we get asked on every first visit.
The one decision that changes the price, the schedule and the finished room.
Read itWhat the City actually requires, including the registration most people miss.
Read itNine things that move the number, and which of them you control.
Read itWhy this job starts with a stamped drawing and not a shovel.
Read itMississauga first, and the parts of the west GTA close enough that a crew is not sitting in traffic instead of in your basement. The older parts of the city are where most of this work is: that housing stock was built when a seven-foot basement was normal, and nobody expected anyone to live down there.
Send us the height from your basement floor to the underside of the joists, and what you want the room to become. That is enough for a straight answer about whether underpinning, a bench footing or neither is the right call.