The numbers that matter
| Situation | Minimum clear height | Where it applies |
|---|---|---|
| Secondary suite in an existing house (Part 11 compliance alternative) | 1.95 m (6'5") | Habitable rooms: bedrooms, living room, kitchen |
| Same suite, under beams and ducts; bathrooms, hallways, laundry | 1.85 m (6'1") | Local low points, not the whole room |
| New construction, living areas | 2.3 m (7'6") | Living room, dining, kitchen, bedrooms in a new house or addition |
| Many municipal second-unit bylaws (varies) | Up to 2.13 m (7'0") | Check your city — some ask for more than the Code minimum |
Two things trip people up. First, the Code measures clear height: finished floor to finished ceiling, after your flooring and drywall go in, not slab to joist. A basement that reads 6'6" to the joists loses an inch to the floor and two to the ceiling and comes in under the line. Second, the lower 1.85 m allowance is for beams, ducts and service rooms — an inspector will not accept a whole bedroom at 1.85 m because there is a duct in one corner.
How to measure your basement properly
- 1Measure slab to the underside of the joists in at least four spots — basements are rarely level and the slab often slopes to the drain.
- 2Subtract the floor build-up you plan to add: subfloor and finish flooring together are usually 25–40 mm (1–1.5 in).
- 3Subtract the ceiling: a fire-rated drywall ceiling on resilient channel is about 40–50 mm; a dropped ceiling is far more.
- 4Note the lowest beam and the lowest duct — those spots must still clear 1.85 m after finishes.
- 5The smallest resulting number is the one the inspector will see.
Why Toronto basements come up short
Houses built before the 1950s were given basements for the furnace and the coal, not for living in; the slab was poured where the footings happened to be, which in Toronto's older neighbourhoods means 6'0"–6'4" is normal. Even 1960s and 70s bungalows and semis in Scarborough, Etobicoke and North York often measure 6'6"–6'10" to the joists, which is fine for a rec room and fails as a suite once the finishes go in. A basement that already clears 7'2" to the joists is the exception — and the cheap conversion.
Your three options when you're short
1. Underpinning — lower the floor, keep every square foot
Underpinning excavates beneath the existing footings in short alternating sections, pours new deeper footings, and then lowers the slab across the whole basement. You choose the depth: 2 ft is standard and takes a 6'3" basement to 8'3"; 3 ft gets you a 9 ft ceiling. It is the only method that keeps the full floor area, and because the new footings are deeper and reinforced, the house ends up on a stronger foundation than it started with. The structural phase runs $35,000–$140,000, with a typical 1,000–1,500 sq ft basement lowered 2 ft at $55,000–$85,000 including engineering, permits and inspections.
2. Bench footing — lower the middle, leave the footings alone
Bench footing pours a sloped concrete bench against the inside of the existing footings and lowers only the floor inside that bench. No work happens under the house, so it is faster and typically 30–40% cheaper than underpinning for the same depth. The cost is floor space: the bench takes 12–24 inches off each exterior wall. In a wide detached basement that is a shelf you can build cabinets on; in a 15-ft-wide semi it is a bedroom you can no longer fit a bed into.
3. Live with it — a non-suite finished basement
A basement that will never be a rental unit does not have to meet the suite height. A family rec room or home office can be finished at the existing height for $60–$90 per sq ft. Just be clear-eyed that it adds living space, not rentable or legally habitable bedrooms, and that a future buyer who wants a suite will price in the lowering you did not do.
Decide on height once. Lowering a basement after it has been finished means tearing out the finishes you paid for. If a suite is even a possibility in the next ten years, underpin now and finish once.
What each option costs in 2026 (GTA)
| Option | Height gained | Floor area | Typical cost |
|---|---|---|---|
| Underpinning, 2 ft | +24 in | Keeps 100% | $55,000–$85,000 (typical 1,000–1,500 sq ft) |
| Underpinning, 3 ft | +36 in | Keeps 100% | Add 20–30% to the 2-ft price |
| Bench footing, 2 ft | +24 in | Loses 12–24 in per wall | 30–40% less than underpinning |
| Finish at existing height | 0 | Keeps 100% | $60–$90 per sq ft, no structural work |
Owner-Operator at Buildoreno with 25+ years of hands-on GTA construction experience. Last reviewed October 2026.