Key takeaways
- Finishing a basement in the GTA typically costs $50,000 to $90,000, and a legal basement apartment typically costs $80,000 to $175,000.
- Our basement finishing starts at $55 per square foot, and our legal basement apartments start at $80 per square foot.
- Ceiling height, water problems, a separate entrance and cutting the slab for drains are the items that move a basement budget most.
- Lowering the floor can add $30,000 to $80,000 or more, and a new separate entrance runs about $30,000, according to published 2026 sources.
- Toronto’s 2026 permit fee is $6.20 per square metre for basement finishing, or $11.53 per square metre plus $56.33 per new unit for an apartment.
- Toronto now pays up to $6,650 per property toward backwater valves, sump pumps and related flood protection, and several other GTA municipalities offer similar subsidies.
Short answer: finishing a basement in the GTA typically costs $50,000 to $90,000 for a standard renovation, and turning it into a legal basement apartment typically costs $80,000 to $175,000. Our own pricing starts at $55 per square foot for basement finishing and $80 per square foot for a legal basement apartment. A new basement bathroom starts at around $20,000. The biggest swing factors are ceiling height (lowering the floor can add tens of thousands), water, a separate entrance, and whether plumbing has to be cut into the slab.
This guide breaks down both kinds of project, prices the line items that move the total, lists the 2026 permit fees and the flood-protection subsidies that can offset part of the cost, and explains where online estimates get the rules wrong. Our own ranges come from projects we quote across Toronto and the GTA; outside figures are labelled with their source and checked in October 2026.
Basement costs at a glance
| Project | Typical GTA cost | What it usually includes |
|---|---|---|
| Standard basement finishing | $50,000 to $90,000 | Framing, insulation, drywall, flooring, lighting, paint, often a bathroom |
| Legal basement apartment | $80,000 to $175,000 | Everything above plus a kitchen, fire and smoke separation, interconnected alarms, code-compliant windows and exits, permits and inspections |
| New basement bathroom | From about $20,000 | More if drains must be cut into the slab or an ejector pump is needed |
Our own pricing starts at $55 per square foot for basement finishing and $80 per square foot for a legal basement apartment. A 1,000 square foot basement therefore starts at about $55,000 finished or $80,000 as a legal suite, before items such as underpinning, a new entrance or waterproofing.
Independent consumer data lines up. HomeStars’ Toronto cost guide (updated August 2026) puts a whole basement renovation at $50,000 to $95,000 and a legal secondary suite at $90,000 to $140,000, rising past $160,000 with underpinning. A contractor quoted in the Globe and Mail in April 2026 put legal suites at around $90,000 to start for 600 to 900 square feet.
Finishing vs. a legal apartment: where the extra money goes
A legal unit is not just a finished basement with a kitchen. To meet the 2024 Ontario Building Code, a two-unit house needs:
- Separation between units: a 45-minute fire separation or, in a house with one secondary suite, a continuous smoke-tight barrier of 15.9 mm Type X drywall.
- Interconnected smoke and carbon monoxide alarms across both units.
- Bedroom windows with at least 0.35 m² of clear opening and no dimension under 380 mm.
- Ceiling height of at least 1.95 m (1.85 m under beams and ducts).
- Sound separation, a compliant exit and heating that does not share return air between units, with alternatives available in houses at least five years old.
- A building permit, inspections and an ESA electrical inspection, plus registration in cities that require it.
Our guide to legal basement apartments in Ontario covers each requirement and the rules city by city.
The line items that move the price
| Item | Published range | Source |
|---|---|---|
| Lowering the floor (underpinning) | Adds $30,000 to $80,000+ | HomeStars Toronto, 2026 |
| New separate entrance | About $30,000 | Contractor quoted in the Globe and Mail, April 2026 |
| Egress window, per window | $3,000 to $6,000 | HomeStars Toronto, 2026 |
| Interior waterproofing | $70 to $230 per linear foot | HomeStars Toronto, 2026 |
| Exterior excavation and membrane | $100 to $300 per linear foot | HomeStars Toronto, 2026 |
| Bathroom rough-in where none exists | $8,000 to $15,000 | HomeStars Toronto, 2026 |
| Kitchen for a suite | $35,000 to $55,000 (kitchenette $20,000 to $35,000) | HomeStars Toronto, 2026 |
These are market figures from published sources, not quotes. What they show clearly is that the expensive items are the ones you cannot see in the finished space: the floor height, the water management and the drains.
Ceiling height decides the budget
If your basement is already at least 1.95 m clear (about 6 feet 5 inches), a legal unit is usually a straightforward project. If it is lower, the floor has to come down, either by underpinning the foundation walls or with a bench footing that steps the new floor in from the walls. That one decision can add more than the rest of the finishing combined, so measure before you dream.
Water comes first
Finishing over a damp basement is the most expensive mistake there is, because the damage shows up after the drywall and flooring are in. Any active leak or seepage has to be fixed first, from the inside or by excavating outside, and a backwater valve and sump pump are worth adding while the floor is open. Older homes in central Toronto are the most likely to need this work.
Drains and the slab
A bathroom or kitchen where there is no rough-in means cutting the slab to reach the drains. If the fixtures sit below the sewer line, an ejector or up-flush system is needed. This is why a basement bathroom starts at around $20,000 rather than the price of an upstairs refresh.
2026 permit fees
Permit fees are a small part of the total. In Toronto, the 2026 schedule charges:
- Basement finishing: $6.20 per square metre.
- Interior alterations for a new unit: $11.53 per square metre of the area affected, plus $56.33 for each new unit.
- Underpinning: $12.37 per linear metre.
- Plumbing fixtures: $23.20 each.
- Minimum fee: $214.79.
For example, a 70 m² basement apartment comes to about $863 in Toronto before plumbing fees. Mississauga refunds the building permit fee for second and third units under its affordable rental program. Drawings by a qualified designer are a separate cost.
Flood-protection subsidies that offset the cost
Several GTA municipalities pay part of the cost of protecting a basement from flooding, which is exactly the work you should do before finishing one:
| Where | What it pays (2026) |
|---|---|
| Toronto | 80% of costs up to: $1,600 per backwater valve (up to two), $2,250 for a sump pump plus $300 for battery backup, $400 for capping the foundation drain connection, and $500 for an assessment. Up to $6,650 per property, expanded May 1, 2026 for work done on or after November 12, 2025. |
| Mississauga | Up to $7,500 in total, including up to $6,000 for a sump pump. Pre-approval required. |
| Peel Region (Mississauga, Brampton) | 60% of a backwater valve, up to $1,500. A basement apartment sharing the house’s sewer line is not eligible. |
| Halton Region (Oakville, Burlington) | 50% of a backwater valve up to $1,600, and up to $6,500 for weeping tile disconnection and a sump pump. |
| Markham | Up to $1,750 for an indoor backwater valve and $5,000 for weeping tile and sump work, in flood-prone areas. |
| Richmond Hill / Vaughan | Backwater valve subsidies of up to $1,500 (Richmond Hill) and $750 (Vaughan). |
| Hamilton | A grant of up to $2,000 plus a loan of up to $2,000. Not available while a secondary unit is being added. |
Programs have conditions, such as licensed contractors, pre-approval or application deadlines, so check the current rules before the work starts.
Where online estimates go wrong
Some widely read cost guides state rules that are not in the Building Code, and they can inflate a budget:
- “A separate entrance is required.” The Building Code does not require one; it requires a compliant way out. Most owners still want a private entrance, and some cities regulate where it goes.
- “Independent HVAC is required.” In a newer house, return air cannot be shared between units, but houses at least five years old can keep one furnace for up to four units with a duct smoke detector that shuts it down.
- “A 45-minute fire separation is required.” In a house with one secondary suite, the 2024 Code allows a smoke-tight barrier of 15.9 mm Type X drywall instead, and older houses have further alternatives.
- Old financing figures. The federal $80,000 secondary suite loan was cancelled before it launched, and the Multigenerational Home Renovation Tax Credit is 14% from the 2026 tax year (up to $7,000), down from 14.5% in 2025.
How long a basement renovation takes
A standard finish is typically 4 to 6 weeks of construction once materials and permits are in place. Adding a bathroom extends that, and a legal apartment, especially with underpinning or a new entrance, takes longer because of the structural work and the extra inspections. For a complete house application, the Building Code sets a 10 business day permit review, and Toronto met its review targets on 87% of applications in 2024.
How to keep a basement budget under control
- Measure the ceiling height and check for water first. Those two answers set the budget.
- Use existing rough-ins and keep wet areas close to the main stack.
- Decide early if it will ever be a separate unit. Building a finish to legal-suite standards later costs more than doing it once.
- Claim the flood subsidies for the valve and sump work you should be doing anyway.
- Compare itemized quotes so you can see what is included. Our guide to vetting a renovation contractor explains how.
Get a real number for your basement
We finish basements and build legal basement apartments across Toronto and the GTA, with permits, inspections and registration handled for you. Book a free consultation for an itemized estimate, and see our basement renovation services. If a suite is part of the plan, our guide to financing a basement suite covers the 90% refinance.
Basement renovation cost FAQs
How much does it cost to finish a basement in the GTA?
Our basement finishing starts at $55 per square foot. A standard basement finish typically costs $50,000 to $90,000 depending on size, finishes and whether a bathroom is included. HomeStars’ 2026 Toronto guide puts a whole basement renovation at $50,000 to $95,000.
How much does a legal basement apartment cost?
Typically $80,000 to $175,000, and ours start at $80 per square foot. Lowering the floor, adding a separate entrance and new bedroom windows are what push a project toward the top.
How much does underpinning add?
HomeStars’ 2026 Toronto guide puts it at $30,000 to $80,000 or more. A bench footing can be a less expensive way to lower the floor, at the cost of a step around the edge of the room.
What does a basement permit cost in Toronto?
Usually a few hundred dollars: $6.20 per square metre for basement finishing, or $11.53 per square metre plus $56.33 per new unit for a basement apartment, with a $214.79 minimum.
Is there a grant for finishing a basement?
Not for finishing itself, but most GTA municipalities subsidize backwater valves and sump pumps, Mississauga refunds the permit fee for second and third units, and an in-law suite may qualify for the federal Multigenerational Home Renovation Tax Credit.
How long does it take to finish a basement?
A standard finish is typically 4 to 6 weeks of construction. Bathrooms, legal suites and underpinning add time.