Additional residential units (ARUs)추가 주거 유닛 (ARU)

What is it?

An additional residential unit (ARU) is an extra home on a lot, besides the main house. A self-contained basement unit (secondary suite), a backyard garden suite and a laneway suite can all be ARUs.

Since a 2022 change to Ontario’s Planning Act, cities cannot block these homes. On a "parcel of urban residential land" with a detached house, semi-detached house or rowhouse (townhouse), a city’s official plan (its big-picture plan) and zoning by-law (its land-use rules) cannot ban up to three units in total, counting the main house (s. 16 (3) and s. 35.1 (1)).

A "parcel of urban residential land" is land in a settlement area where homes are allowed and that is connected to municipal sewers and municipal drinking water (definition in s. 1). Rural land without these services is not covered.

The three cases the law protects

The law counts the units inside the main house and the units in backyard buildings separately. In every case the total is up to three units on one lot.

This is the minimum a city cannot block. A city can allow more. For example, Toronto allows fourplexes (4 units) city-wide.

What a city cannot require

• Parking: a city cannot require more than one parking space for each extra unit that is not the main unit (s. 35.1 (1.1)).
• Minimum size: a zoning by-law cannot set a minimum floor area for an extra unit (s. 35.1 (1.2)).
• Any zoning rule that breaks these limits has no effect to that extent (s. 35.1 (1.3)).
• Provincial regulation O. Reg. 462/24 (in force November 20, 2024): according to the City of Toronto, where a lot ends up with three units or fewer, no angular plane applies, the minimum distance between the house and a backyard suite is 4 m (7.5 m if the suite is taller than 4 m), the maximum lot coverage (the share of the lot covered by buildings) is 45%, and there is no maximum floor space index. Where the City’s rules are more generous, the City’s rules apply.
• We did not open the text of the regulation itself for this page. Confirm the details with the City or your designer.

No appeals against ARU rules

There is no appeal to the Ontario Land Tribunal (OLT) against official plan policies or parts of a zoning by-law passed to allow ARUs (s. 17 (24.1) and s. 34 (19.1)). The only exception is an appeal by the Minister.

So a neighbour cannot use an appeal to stop the city’s ARU rules themselves.

But if your project does not meet a zoning rule (height, setbacks and so on) and you need a minor variance (a small exception to the zoning rules), the people listed in the Act can appeal that decision. In Toronto, that appeal goes to the Toronto Local Appeal Body (TLAB).

In Toronto

• Secondary suites: one is generally allowed inside a detached house, semi-detached house or townhouse (it must meet section 150.10 of Zoning By-law 569-2013). It is a self-contained home with its own kitchen and bathroom.
• Multiplexes: a building with 2 to 6 homes. Four-unit multiplexes are allowed city-wide, and six-unit permissions vary by location (now allowed in Toronto & East York District and Ward 23). City Council adopted the six-unit changes on June 25-26, 2025.
• Garden suites: a backyard building not on a public lane. One garden suite (one unit) is allowed per lot, with a footprint of no more than 60 m².
• Laneway suites: allowed on lots that share a property line with a public lane, up to 8 m wide by 10 m long.
• "As-of-right": if your plan meets the zoning rules, you can apply for a building permit without a rezoning or a minor variance.
• Lots still zoned under a former by-law (for example the former North York or Etobicoke zoning codes) are not covered by the garden suite changes. Call Toronto Building at 416-397-5330.

Permits and the Building Code still apply

Even when zoning allows an ARU, you need a building permit for the work. No one may build or demolish a building without a permit from the city’s chief building official (Building Code Act, s. 8 (1)). Changing how a space is used can also need a permit, even with no construction, if it makes the building more hazardous (s. 10 (1)).

You must also meet the Ontario Building Code, tree protection rules and fire access rules. Toronto says fire access for garden suites is set through a Building Code review, not zoning, and cannot be changed with a minor variance.

Toronto suggests getting a zoning review (Zoning Applicable Law Certificate) before the permit. If part of your plan does not meet zoning, you must first apply to the Committee of Adjustment for a minor variance.

Development charges and taxes

• Development charges (fees a city charges on new buildings): the law exempts a second and third unit in an existing or new house, and one unit in a backyard building (Development Charges Act, s. 2 (3.2) and (3.3)).
• Toronto: the Municipal Code (415-6(A)(2)) exempts the second, third and fourth units from development charges where there are no more than 4 units in total on the lot. For parkland dedication (land for parks, or money instead, that a city can ask for when you build), the Municipal Code (415-30(A)(16)) exempts a second, third or fourth unit in the main building and one backyard unit. This applies only where there are no more than 5 units in total on the lot. Ask the City whether your plan qualifies.
• Property tax: we could not confirm whether or how much MPAC’s assessment changes when you add a unit. Check with MPAC and your city.
• Rent you earn may be taxable, and renting part of your home can affect the principal residence exemption when you sell. Check with an accountant.

Watch out when you buy or rent out

• "ARUs are allowed" is not the same as "this unit is legal". Check the city’s permit records to see whether an existing basement unit or backyard building got a permit and passed final inspection. Toronto treats a backyard building built without a permit as a "new building" under current rules, no matter how old it is.
• In Toronto you cannot sever (split) the lot so the main house and a garden suite end up on two separate lots. The suite cannot be sold on its own.
• If you have a tenant, the Residential Tenancies Act (RTA) applies. It does not apply if the tenant must share a kitchen or bathroom with the owner or the owner’s close family who live in the same building (RTA s. 5 (i)).
• A unit first created after November 15, 2018 may, under certain conditions, be exempt from the rent increase guideline (RTA s. 6.1). See "Rent control exemption".
• This protection covers detached houses, semis and rowhouses only. A condo apartment unit is not covered, and for a condo townhouse you must also check the condo declaration and rules. Ask a lawyer.

Example