Legal Basement Apartment in Ontario: Rules and Permits (York Region Guide)

General information only, current as of October 2026. Rules change and every property is different, so confirm requirements with your municipality before you start.

What counts as a second unit?

Ontario calls these additional residential units (ARUs). The Town of Newmarket describes an ARU as a separate living unit within your house, including basement apartments and in-law suites. If you rent a room but share the entrance, kitchen or bathroom, that isn't an ARU (Town of Newmarket).

The provincial picture

Through Bill 23 (the More Homes Built Faster Act, 2022), Ontario changed the Planning Act to allow, "as-of-right" (without rezoning), up to three units per lot in many existing residential areas. That can be up to three units in the main house, or two in the house and one in an ancillary building such as a garden or laneway suite (Environmental Registry of Ontario 019-5286).

"As-of-right" zoning doesn't remove the need for a permit. The province's own guide, Add a second unit in your house, says the first step is to speak with your municipal planning and building departments, and that adding a second unit requires a building permit. It also notes:

• A house more than five years old is treated as an existing house under the Building Code, which allows more flexibility when renovating. Newer houses generally have to meet new-construction requirements.
• Development charges are not collected for building a second unit in an existing house.
• Every second unit, new or existing, must be a safe place to live.

The codes that apply

Ontario Building Code

The current code is O. Reg. 163/24, the 2024 Building Code, in force since January 1, 2025. For second units it sets requirements such as fire separations between units, exits, smoke and carbon monoxide alarms, ceiling heights, windows, plumbing, heating and ventilation. Your designer and building department will confirm which requirements apply to your house.

Ontario Fire Code

The Fire Code (O. Reg. 213/07) includes retrofit requirements for existing two-unit houses in Part 9 (Section 9.8, "Two Unit Residential Occupancies"), covering fire separations, means of escape, alarms and electrical safety. Local fire services enforce it.

Electrical safety

Electrical work must be done by a Licensed Electrical Contractor under an Electrical Safety Authority (ESA) permit, and inspected. You can verify a licence with the ESA Contractor Locator. Some municipalities ask for ESA documents when you register the unit.

York Region: municipal steps

Newmarket

• Zoning check first. The Town's 2024 ARU homeowner package describes obtaining a Zoning Preliminary Review letter before applying for a building permit through the Town's Development Portal (ARU package).
• Building permit before any construction starts.
• Registration. Newmarket has required ARUs to be registered since 2013 (By-law 2013-13). For a new ARU, the application follows construction and includes the final building inspection report, ESA compliance reports for both units, a parking sketch and the application form. Registered units receive an "N" plate, and the unit is given a "B" address (Register your ARU).

Aurora

• Aurora's zoning permits second suites in detached, semi-detached and link houses, subject to conditions (Town of Aurora).
• A building permit (or change-of-use permit) is required.
• Aurora's Registration By-law 6660-24 requires every owner to register their ARU, allows up to three units including the principal dwelling, and requires each ARU on a property to be registered separately.

Richmond Hill

• Richmond Hill permits ARUs subject to zoning (Zoning By-law 143-24) and requires a building permit for a new unit. Its submission list includes drawings by a qualified designer and mechanical (heating and cooling) calculations (City of Richmond Hill).

East Gwillimbury and King Township (Schomberg)

Contact the Town of East Gwillimbury or the Township of King building department before you start. The same provincial framework applies, but zoning details, submission requirements and any registration rules are set locally.

A typical project path

1. Feasibility visit: ceiling heights, windows and exits, layout, moisture, parking and mechanical systems.
2. Zoning confirmation with the municipality.
3. Drawings prepared by a qualified designer.
4. Building permit application and approval.
5. Construction with inspections at required stages, plus an ESA permit and inspection for the electrical work.
6. Final inspection.
7. Registration with the municipality, where required.

Common sticking points

• Ceiling height under beams and ducts in older basements
• Exits and windows: bedrooms and the unit need safe ways out
• Fire separation between units, including doors, ceilings and ductwork
• Interconnected smoke and CO alarms across both units
• Heating and ventilation that meet the Code for two units
• Moisture: dealing with any water issues before finishing
• Parking requirements set by the local zoning

How BDF helps

BDF Renovation and Construction Inc. builds legal basement apartments to code, with permits handled when they're needed, and coordinates inspections. Electrical, plumbing and HVAC work is completed through our licensed partner contractors. Final approval always rests with the municipality, so we'll never promise guaranteed approval. We'll tell you honestly what we see at the free on-site estimate. Work we perform comes with a 1-year warranty.

Learn more on our legal basement apartment page. We serve Newmarket, Aurora, Richmond Hill, East Gwillimbury, Schomberg and surrounding areas. Planning the unit's kitchen and bathroom? See kitchen and bathroom renovation.