Multiplex · Southern Ontario
Multiplex Builder in Southern Ontario
Perimeter Homes builds duplexes, triplexes and fourplexes across Southern Ontario, stick-built or modular. Start with what your city actually allows.
Ontario rules
Duplex, triplex and fourplex rules
Ontario's Planning Act and O. Reg. 299/19 allow up to three residential units on a serviced urban residential lot, either three in the house or two in the house plus one in a backyard building. O. Reg. 462/24 adds a 45% lot coverage allowance and lifts floor space index limits on those lots. Some cities go further: Toronto permits fourplexes in Neighbourhoods city-wide.
Province
Up to three units as of right on a parcel of urban residential land, subject to local height and setback rules.
Source: O. Reg. 299/19 (as amended by O. Reg. 462/24), as of November 1, 2026Toronto fourplexes
Duplexes, triplexes and fourplexes are permitted in the R, RD, RS, RM and RT zones. At least one unit must sit fully or partly above another.
Source: City of Toronto: Considerations when building multiplexes, as of November 1, 2026Real Perimeter project
102 Shaver Ave N, Etobicoke
A completed stick-built fourplex: two 1-bedroom-plus-den and two 2-bedroom units. See the project.
By municipality
How many units, city by city
What each city or county allows on a residential lot, from its own published rules. Always confirm your lot's zone.
Ancaster
Ancaster is part of the City of Hamilton. Hamilton says a lot can have up to four dwelling units in some zones, made up of the main house plus internal and detached additional dwelling units. Some Ancaster lots are still under the former Ancaster Zoning By-law 87-57.
Source: City of Hamilton: ADUs, as of November 1, 2026Hamilton (incl. Stoney Creek, Waterdown)
Hamilton says a lot can have up to four dwelling units in some zones (the main house plus internal and detached additional dwelling units), and its ADU team reviews permits for houses with up to two internal units and one detached unit.
Source: City of Hamilton: ADUs, as of November 1, 2026Dundas
Dundas is part of the City of Hamilton. Hamilton says a lot can have up to four dwelling units in some zones, made up of the main house plus internal and detached additional dwelling units.
Source: City of Hamilton: ADUs, as of November 1, 2026Burlington
Burlington's Zoning By-law 009-2026 allows up to three additional residential units on urban residential land where a detached house, semi, street townhouse or rear lane townhouse is permitted. That is up to four units in total.
Source: Burlington Zoning By-law 009-2026, s.5.14, as of November 1, 2026Oakville
Oakville's Zoning By-law 2014-014 (s.4.1.2) allows two attached additional residential units, or one attached plus one detached, with a detached house, semi, linked house or townhouse. By-law 2024-053 proposed three units on some lots, so confirm the current permissions.
Source: Oakville Zoning By-law 2014-014, Part 4, as of November 1, 2026Mississauga
Mississauga allows up to two additional residential units with a detached, semi-detached or townhouse home, and the city lists "a new build with up to three units" as one option.
Source: City of Mississauga: ARUs, as of November 1, 2026Etobicoke
Toronto's By-law 474-2023 permits duplexes, triplexes and fourplexes in the R, RD, RS, RM and RT zones city-wide, so up to four units. Lots still zoned under the former Etobicoke Zoning Code may differ.
Source: City of Toronto: Multiplex study, as of November 1, 2026Toronto
Toronto's By-law 474-2023 permits multiplexes of up to four units in Neighbourhoods city-wide (R, RD, RS, RM and RT zones), within roughly the same envelope as a detached house. Multiplexes are exempt from FSI and can be up to 10 m tall where the zone limit is lower.
Source: City of Toronto: Multiplex study, as of November 1, 2026Scarborough
Toronto's By-law 474-2023 permits duplexes, triplexes and fourplexes in the R, RD, RS, RM and RT zones city-wide, so up to four units. Lots still under former Scarborough zoning may differ.
Source: City of Toronto: Multiplex study, as of November 1, 2026Pickering
Pickering's By-law 8036/23 allows one additional dwelling unit inside a detached, semi or townhouse dwelling and one in an accessory building, so three units in total.
Source: Pickering By-law 8036/23, as of November 1, 2026Ajax
The Ajax Zoning By-law (Section 4.4, March 2026 consolidation) allows combinations of up to two attached accessory dwelling units plus one detached unit, so up to four units.
Source: Ajax Zoning By-law, Section 4, as of November 1, 2026Whitby
Ontario's Planning Act allows up to three units on a serviced urban residential lot. Whitby's By-law 8143-24 sets the standards for an additional unit in an accessory structure (75 m², 5.5 m tall).
Source: Whitby By-law 8143-24, as of November 1, 2026Oshawa
Oshawa allows up to three residential units on a lot, with at most one in an accessory building, in its R1, R2, R3, R5 and specified other zones.
Source: City of Oshawa: Accessory apartments, as of November 1, 2026Niagara (incl. Grimsby)
Niagara Region doesn't zone land. Each local municipality has its own by-law. In Grimsby, Zoning By-law 14-45 (s.4.19) allows up to two additional residential units on serviced residential and downtown lots, so three units in total.
Source: Grimsby Zoning By-law 14-45, as of November 1, 2026Brantford
Brantford's Zoning By-law 124-2024 (s.3.2) allows additional dwelling units in single detached, semi-detached, street and block townhouses and in accessory structures, up to three units per lot.
Source: Brantford Zoning By-law 124-2024, as of November 1, 2026Caledon
Caledon's Zoning By-law 2006-50 (s.6.4) allows up to three additional residential units on lots with a detached, linked, semi-detached or townhouse dwelling, subject to provincial plans.
Source: Caledon Zoning By-law 2006-50, s.6, as of November 1, 2026Milton
Milton's Zoning By-law 016-2014 (s.4.10, March 2026) allows up to three additional dwelling units on detached, semi, semi-link and townhouse lots served by municipal water and wastewater, so four units in total.
Source: Milton Zoning By-law 016-2014, as of November 1, 2026Haldimand & Norfolk
Haldimand County's HC 1-2020 (as amended March 2025) allows up to two additional dwelling units per lot, with at least one inside the main house if there are two. Norfolk County permits Additional Residential Dwelling Units under its own by-law.
Source: Haldimand by-law amending HC 1-2020, as of November 1, 2026Kitchener
Kitchener says up to four dwelling units are permitted on residential lots under its zoning by-law, though lot width, servicing or hazards can limit some lots to one or two.
Source: City of Kitchener: ADUs, as of November 1, 2026Cambridge
Cambridge allows up to two additional residential units on a lot with a detached, semi or townhouse (three units in total), under Section 4.19 of its new Zoning By-law 26-007.
Source: City of Cambridge: ARUs, as of November 1, 2026Waterloo
Waterloo's Zoning By-law 2018-050 allows up to four units on low-rise residential property. A property can have one coach house containing one or two units.
Source: City of Waterloo ARU Guide, as of November 1, 2026Check with the city: unit permissions depend on your zone, servicing and lot size, and several of these by-laws were amended in 2025 and 2026.
Multiplex models and process · Southern Ontario service area
Common questions
FAQ
Can I build a fourplex in Toronto?
Yes, where the lot is in an R, RD, RS, RM or RT zone, under By-law 474-2023, within the multiplex built-form standards.
How many units does Ontario allow on a lot?
Up to three on a serviced urban residential lot under the Planning Act and O. Reg. 299/19. Some municipalities allow four.
Have you built a multiplex?
Yes, a stick-built fourplex at 102 Shaver Ave N in Etobicoke.
Do you build stick-built or modular multiplexes?
Both. The right choice depends on the lot, the city and the timeline.
Start here
Talk to a multiplex builder.
Dan Carrol and the Perimeter Homes team reply within one business day. A phone number is required so we can call you about your lot.