Underpinning takes 4 to 6 weeks of on-site work, inside a 3 to 6 month total timeline once engineering, permits and curing are counted. The work proceeds in alternating sections, never all at once, because the undisturbed sections hold the house up while their neighbours are open.
Here is what actually happens, including the parts that are unpleasant and that nobody mentions until you are living through them.
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Where the months actually go
Weeks, drawn to scale. Four to six weeks is the crew. Three to six months is the project.
- Design and engineering2–4 wks
Site visit, drawings, engineer’s seal
- City permit review6–12 wks
Outside anyone’s control. The longest single item
- Mobilisation1 wk
Protection, access, bin, utility locates
- Excavation and pours4–6 wks
The noisy phase. Longer for a row house
- Slab and cure2–4 wks
New slab, then curing before loading
- Backfill and restore1–2 wks
If exterior work was in the scope
End to end 16 to 29 weeks, which is roughly 3 to 6 months
The red bar is the City permit review, and it is the single longest item in the project. It cannot be accelerated by paying more, and a contractor who quotes a total timeline without asking when you plan to submit has not accounted for it. What living through it is actually like.
Before anything is dug
Weeks 1-3: engineering. A licensed structural engineer visits, assesses the existing foundation and soil, and prepares sealed drawings specifying footing depths, section widths, reinforcement and the excavation sequence.
Weeks 3-15: permit review. The City of Toronto reviews the application. This is currently 6 to 12 weeks and is largely out of everyone's control. Use it to finalise decisions about waterproofing, walkouts and finishing.
On site
Week 1: setup and access. Protection goes down over floors and stairs, dust barriers go up, and the soil removal route is established. If the house has no rear access, this is when it becomes obvious that every wheelbarrow travels through the interior.
Weeks 1-4: the sequence. Sections roughly three to four feet wide are excavated beneath the existing footing, one alternating set at a time. Each is formed, reinforced, poured and left to gain strength before the adjacent sections are opened. This repeats around the perimeter. It is slow by design.
Weeks 3-5: interior excavation and services. The middle of the floor is dug to the new depth. Plumbing that ran under the old slab, including drains and often the sewer connection, is exposed and frequently updated at this point since it will never be this accessible again.
Weeks 4-5: waterproofing and drainage. Interior weeping tile, a sump if needed, and a vapour barrier. If exterior waterproofing is in scope, it happens while the foundation is exposed.
Weeks 5-6: the new slab. Gravel, insulation where specified, vapour barrier, reinforcement, then the pour.
Weeks 6-8: curing. Concrete gains usable strength over days but continues curing for weeks. Finishing work, especially flooring, should wait. Rushing this is how flooring fails months later.
What it is actually like to live through
The short version is below. The full account of living through an underpinning, including whether you should move out, is on its own page.
The dust and the noise are worse than people expect. The disruption is not the concrete, it is the four to six weeks of it.
- Noise: jackhammering and concrete work through the working day, most days
- Dust: controlled by barriers, never eliminated. Expect fine dust upstairs
- Access: the basement is a construction site and off limits for the duration
- Soil: cubic metres of it leaving the property, often through the interior in tight lots
- Vibration: picture frames and shelves upstairs will need attention
- Services: short planned interruptions to water or drainage during the plumbing stage
Many homeowners stay through it. Some with young children or working from home choose not to. It is worth deciding deliberately rather than discovering it in week two.
Signs the work is being done properly
- Sections are alternating, not a continuous open trench along a wall
- Each pour is allowed to cure before adjacent sections open
- The sequence matches the stamped drawings, not a crew's improvisation
- Inspections happen at stages, and the crew expects them
- The engineer is reachable and involved, not a name on page one
- Soil is removed, not piled against the foundation
If a crew has an entire wall open at once, stop and call the engineer. That is the single clearest warning sign in this trade.
Common questions
How long does underpinning take?
4 to 6 weeks of on-site work for a typical Toronto home, within a 3 to 6 month total timeline including engineering, the 6 to 12 week permit review, and curing.
Can I live in the house during underpinning?
Usually yes. The basement is off limits and the upper floors stay habitable, but expect daily noise, dust and vibration for several weeks. Households with infants, shift workers or full-time home offices often arrange to be elsewhere for the loudest stretch.
Why is it done in sections instead of all at once?
Because the undisturbed sections support the house while the open ones are excavated and poured. The alternating sequence is specified by the engineer and is the core safety principle of the entire method.
When can I finish the basement afterward?
Framing can usually begin shortly after the slab is poured, but flooring should wait until the slab has cured and moisture-tested appropriately. Rushing flooring onto a green slab is a common and expensive mistake.
Will underpinning damage my house?
Properly engineered and sequenced, no. Minor settlement cracks in drywall upstairs are possible and normally cosmetic. Structural problems come from compressed or skipped sequencing, which is what the drawings and inspections exist to prevent.
What happens if they find bad soil or an unexpected footing?
Work pauses and the engineer revises the approach. This is the most common source of change orders, which is why an honest quote includes a contingency rather than pretending the ground is fully known in advance.
Get a real range
Not a brochure. Tell us the basics and we will come back with numbers that reflect your actual foundation.