Underpinning vs bench footing
The one decision that changes the price, the schedule and the finished room.
Read itFAQ
Questions we get asked every week
Fifteen of them, answered the way we would answer them standing in your basement.
What is basement underpinning?
It is the process of extending a foundation downwards. Short sections of the wall are excavated below the existing footing and filled with new concrete, one round at a time, until the whole perimeter bears at a lower level. Once it does, the floor can be dug out and rebuilt lower. See the full explanation.
How is the house held up while you dig underneath it?
By the ground and concrete on either side of every open section. The perimeter is divided into short numbered sections, and only non-adjacent ones are ever open at the same time. The existing footing spans the gap. Each section is poured and left to cure before its neighbours are touched.
How long does an underpinning job take?
Weeks rather than days, and the curing time between rounds is a large part of that. The variables are how much perimeter is involved, how deep you are going and how quickly material can move in and out of the house. Anyone quoting a few days for a full perimeter is describing a different job.
What does it cost?
We do not publish a number, because the two things that move it most — access to the house and how much depth you are adding — cannot be assessed remotely. Here are the nine factors that actually drive the figure, so you can judge a quote when you get one.
Do I need a building permit?
Yes. Excavating below a footing and pouring new foundation is structural work on a house, and in Ontario that means drawings from a qualified designer and a building permit before the work starts. So does benching. More on permits and engineering.
Underpinning or a bench footing — which do I need?
The deciding question is whether the perimeter of that basement is space you were planning to use. Bench footings are cheaper and faster and take a permanent strip around every wall they run along. Underpinning costs more and leaves the room intact. Full comparison here.
How much extra height can I actually gain?
It is decided by the drawings, and usually limited by the depth of the buried drain line under your existing slab and by the soil and water at the new level. Homeowners are often surprised by the answer, which is why we measure and look for the drain before anyone talks about numbers.
Can I stay in the house during the work?
In most cases yes. It is loud, dusty work with a lot of material moving through the property, so dust separation and a protected route matter. The basement itself is unusable from the day the slab comes out until the new one is poured.
Do you handle the drainage as well?
Yes, and it is not optional. Lowering the floor puts it closer to groundwater, and the original weeping tile ends up above the new level, so it cannot serve it. A new tile at the new footing level, clear stone, a sump pit and pump and a vapour barrier go in before the slab. More on drainage for a lowered floor.
Will you finish the basement afterwards?
We hand back a bare, level, drained concrete floor with the drainage in and the sump running. Framing, insulation, plumbing fit-out, drywall and finishes are a separate trade and a separate budget. Comparing quotes is only meaningful when both stop at the same point.
Does underpinning make a basement apartment legal?
No — it can make it possible. A legal second unit in Mississauga needs to satisfy the Building Code, the Fire Code and zoning, be built under a permit, pass its inspections, and then be registered with the City. Ceiling height is one requirement among several. Read the second-unit guide.
My basement wall has a crack. Is that an underpinning job?
Usually not. Most cracks are a repair or a waterproofing question rather than a bearing one. Underpinning becomes the answer when a footing has settled because the ground beneath it will not carry it. How to read what the wall is telling you.
Can you underpin a semi-detached or a townhouse?
Yes, and the party wall changes the design and the conversation with your neighbours. It has to be dealt with on the drawings from the start, so raise it at the first visit rather than at permit stage.
What happens if you find something unexpected under the floor?
Old fill, a buried footing, an unrecorded drain, or more water than expected. It happens. What matters is that the contract says in advance how a change like that is priced and approved, so it is a conversation rather than a surprise invoice.
Do you work outside Mississauga?
Yes, in the nearby west GTA where the drive does not consume the working day. Areas we cover.
Still unsure?
Send the height from your floor to the underside of the joists and a photograph of the wall. That answers most of these questions for your house specifically.
Longer answers
Four guides that go further than a paragraph.
Not on the list?
Ask it directly. We would rather answer a question early than quote a job that was never the right one.