Know the number before you dig.
Underpinning is the most expensive thing most people do to their house, and it is invisible once finished. So quotes vary by double and nobody explains why. We publish the real ranges, the permit fees, the engineering costs, and what actually drives the price.
- 01Existing footing, undisturbed
- 02New concrete, poured deeper
- 03Alternating sections, never all at once
- 04New slab at the lower level
- 05Waterproofing while exposed
- 06Headroom gained: 2 to 4 feet
Section through an underpinned foundation. Amber sections are poured first, then the adjacent ones, so the house is never unsupported.
01 · What you probably came here to find out
Every number the industry normally makes you call for.
Thirteen guides covering cost, method, permits, process and the parts nobody volunteers. No gates, no forms in the way.
What underpinning actually costs
$500-750 per linear foot, the permit fee, the engineering, and why two quotes for the same basement differ by double.
→02Benching vs underpinning
Benching costs 20-40% less but permanently eats 18-24 inches around the perimeter. The measurement that settles it.
→03Basement lowering
Going from a 6-foot basement to 7 foot 6 or more. How much depth is achievable, and what governs it.
→04Basement walkouts
$15,000-30,000 on top of underpinning, and far cheaper bundled than added later. Grade and drainage decide the price.
→05Permits and engineering
$11.89 per linear metre to the City, stamped engineer drawings required, and a 6-12 week approval wait nobody mentions.
→06The process, week by week
The alternating-section sequence, the real 3-6 month timeline, and how to tell the work is being done properly.
→07How to compare quotes
The twelve line items to demand, the five variables behind a 2x spread, and the questions that reveal real experience.
→08Legal basement apartments
Second suites are allowed city-wide. Ceiling height is what stops them, and 6 ft 5 in is the number that matters.
→09Is it worth it?
$70-150 per sq ft against $400-650 for an addition. Run against moving, including the cases where the answer is no.
→10Semis and row houses
Party wall foundations change the engineering, the sequence and the price. Condition surveys and the neighbour conversation.
→11Waterproofing
Exterior $150-350 per linear foot, interior $80-180, and why doing it during underpinning costs a fraction of either.
→12Foundation cracks
Direction tells you more than width. Which cracks are cosmetic, which are structural, and what each costs to fix here.
→13Living through it
The noise, the dust, the real timeline, and an honest read on whether you can stay in the house.
→02 · Why quotes differ by double
Five questions that make three quotes comparable.
A 2x spread between underpinning quotes is normal, and it almost never means one contractor is twice as greedy. It means the quotes are for different work, each priced honestly, with nothing on the page telling you so. Ask every bidder these five, in this order.
Is waterproofing included?
The single most common difference between two quotes. The foundation is accessible exactly once in the life of the house, and the marginal cost while it is open is a fraction of the standalone price.
Are permits and engineering in the number?
A quote that excludes the $1,500 to $2,500 engineering package and the City permit fee looks cheaper and is not.
How deep, exactly, and measured to what?
Two feet and four feet are not proportional in cost. Ask for the finished floor-to-ceiling height in writing, not the depth to the underside of the joists.
Is the new slab included?
Sometimes quoted separately, occasionally forgotten. The same applies to the gravel base, the vapour barrier and any bathroom rough-in.
What is the soil contingency?
Nobody knows the ground for certain until they dig. An honest quote carries a contingency or states plainly what happens if conditions differ.
03 · Work it out yourself
Three tools, no email address required.
Built from the same published Toronto figures as the guides. They will not tell you what a contractor will charge, but they will tell you whether the number in front of you is sane.
Cost calculator
Your perimeter and target height, itemised into a range you can take to a contractor.
Open it →Tool 02Quote scorecard
Three bids, normalised to the same scope, so you can see what the real difference is.
Open it →Tool 03Method decision tool
The width subtraction that settles benching versus underpinning in about a minute.
Open it →04 · The honest version
What underpinning is really like.
The parts that get left out of the sales conversation, because they are the parts people find out about in week two.
It is mostly waiting
4 to 6 weeks of work, but 3 to 6 months in total. The City permit review alone is 6 to 12 weeks and nobody can speed it up.
The disruption is real
Jackhammering most days, fine dust upstairs despite barriers, and in a tight lot every wheelbarrow of soil comes out through your house.
The sequence is the safety
Sections are poured in alternating order so the house is never unsupported. If a crew has a whole wall open at once, stop and call the engineer.
Do the waterproofing now
The foundation is accessible exactly once. Doing it later means excavating the perimeter a second time at far greater cost.
05 · Common questions
How much does basement underpinning cost in Toronto?
$500 to $750 per linear foot of foundation wall, or roughly $70 to $150 per square foot of basement floor. For a typical home with 100 to 140 linear feet of perimeter, that is $50,000 to $105,000 before permits and engineering.
How long does underpinning take?
4 to 6 weeks of on-site work, but 3 to 6 months end to end once you count the engineer’s drawings, the 6 to 12 week City permit review, and slab curing.
Do I need a permit and an engineer?
Yes to both. A building permit is required, and it will not be issued without stamped structural drawings from an engineer licensed in Ontario.
Should I choose benching instead?
Sometimes. Benching costs 20 to 40 percent less but permanently gives up 18 to 24 inches around the perimeter. In a wide basement that is a fair trade. In a narrow Toronto semi it usually is not.
Why do quotes vary so much?
Because they usually cover different scopes: waterproofing in or out, permits and engineering in or out, depth of lowering, and whether the new slab is included. Itemise those five things and quotes converge.
Get a real range
Not a brochure. Tell us the basics and we will come back with numbers that reflect your actual foundation.