A basement unit can bring in rental income or house a family member, and provincial law now allows one in most GTA houses. Ontario’s 2024 Building Code and your city’s permit process decide whether yours can become one. These are the steps from idea to occupancy.
1. Confirm that zoning allows it
The More Homes Built Faster Act, 2022 amended Ontario’s Planning Act so that municipalities cannot prohibit up to three units on a parcel of urban residential land: three in a detached house, semi or rowhouse, or two in the house and one in a building such as a garden suite. Official plans and zoning by-laws also cannot require more than one parking space for each additional unit. Your city’s zoning still sets the details.
- Toronto has separate permit paths for a secondary suite and for converting a house into a multiplex, from a duplex up to a sixplex where zoning allows.
- Vaughan allows suites only in eligible detached, semi-detached and street townhouses, not in a floodplain or the Woodbridge Special Policy Area, and requires one extra parking space per unit.
- Mississauga allows up to two additional units, or a fourplex, on a detached, semi-detached or townhouse property.
2. Check what your basement can support
Measure three things first. They drive the design and much of the cost.
- Ceiling height. Ontario’s code requires at least 1.95 m in a secondary suite, and 1.85 m clear under beams and ducts. Falling short means lowering the floor or rerouting ducts, both costly.
- Bedroom windows. Unless a door on the same level opens directly outside, every floor level with a bedroom needs at least one outside window that opens from inside without tools, with an unobstructed opening of at least 0.35 m² and no dimension under 380 mm. A window opening into a window well needs at least 550 mm of clear space in front of it. Enlarging a basement window means cutting the foundation wall.
- The entrance. A new below-grade entrance, if the unit needs one, requires a permit in Toronto and Mississauga and adds excavation, a stair and drainage.
3. Get drawings and a building permit
You need a building permit to create a unit, and Vaughan treats a secondary suite as a separate permit from a basement finish. Toronto’s secondary suite application asks for a site plan, floor plans showing each room with smoke alarm, carbon monoxide alarm and plumbing fixture locations, cross-sections with floor-to-ceiling heights, and stair and guard details. Vaughan requires drawings by an architect, a professional engineer or a qualified designer. HVAC and plumbing permits run alongside, and electrical work needs an ESA permit, done by a Licensed Electrical Contractor if you hire it out.
Allow for review time. Mississauga lists 15 business days for the first review of a complete second-unit application and an average of 10 weeks to issue the permit. One cost you avoid: the Development Charges Act exempts a second or third unit in an existing detached house, semi or rowhouse from development charges, within the limits it sets.
4. Build the fire and life-safety items
- Fire separation. The 2024 code accepts a continuous, smoke-tight layer of 15.9 mm (5/8 in) Type X gypsum board on both sides of the walls and under the floor framing between units, and waives the rating in a sprinklered house. In an existing house, a Part 11 alternative accepts a 15-minute floor separation where smoke alarms in every unit and common area are interconnected.
- Smoke alarms on every storey, in each bedroom, outside the bedrooms and in any shared hallway or common area. They are hard-wired with battery backup, include a visual signal, and are interconnected so one alarm sounds them all in both units.
- Carbon monoxide alarms beside each bedroom, and on each storey without one, in a unit that has a fuel-burning appliance, gets warm air from a fuel-burning furnace, or shares a wall, floor or ceiling with a furnace room or garage.
- Heating. In an existing house with up to four units, Part 11 lets the existing system be altered to serve both units if each unit has smoke alarms and a smoke detector in the ductwork shuts off the furnace’s fuel and power. A separate system for the suite avoids that and gives each unit its own thermostat.
5. Pass inspections and close the permit
Toronto’s inspection list for houses shows the usual sequence: framing with plumbing and HVAC rough-ins, fire separations before interior finishes go on, insulation and vapour barrier, then final and occupancy inspections. Close the permit at the end, because open permits can hold up a sale.
6. Register the unit where your city requires it
Mississauga requires every second unit to be registered with the City. Registration is free once all inspectors have signed off the permit. Toronto asks for a Rental Renovation Licence screening form with the permit application, and Vaughan sends suites built before July 14, 1994 to Vaughan Fire and Rescue Service for a fire code inspection. Check your city’s rules before a tenant moves in.
How MKC can help
MKC Group takes basement units from first measurements to final inspection. Our in-house engineering department prepares the drawings and engineering, we apply for the permits, and our crews build the unit, including the mechanical work MKC started with. Financing is available on eligible projects through Financeit, which sets approval, rates and terms. Call (647) 637-6052 for a free estimate.