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Accessory Dwelling Units
Accessory Dwelling Units designed, permitted and built across the 30 municipalities of the Greater Toronto Area - zoning review, permit drawings and construction handled by one team.
Accessory Dwelling Units - Overview
Key Takeaways
- Key features: Feasibility and lot review before you commit, Design, permit and build under one contract, Zoning and by-law handling for all 30 GTA municipalities
Full-service accessory dwelling unit design and construction across the GTA - we take a single-family lot from feasibility review through permit approval, build and final occupancy sign-off on one contract.
Features & Specifications
- Feasibility and lot review before you commit
- Design, permit and build under one contract
- Zoning and by-law handling for all 30 GTA municipalities
- Fixed-scope pricing before construction starts
- Occupancy sign-off and final inspections included
Key takeaways
- An accessory dwelling unit is a second, self-contained home on a lot that already holds a house - its own entrance, kitchen, bathroom and services, legally recognised as a separate dwelling.
- Ontario recognises four physical forms: a detached garden suite or laneway house, an internal basement or upper-floor suite, a garage conversion, and a factory-built module.
- Bill 23 permits up to three residential units as-of-right on most serviced GTA lots, so the six-to-twelve-month rezoning application is no longer the default path.
- A typical detached 500-600 sq ft unit runs $200,000 to $350,000 in the GTHA; permit review takes four to eight weeks and the honest end-to-end range is eight to fourteen months.
Accessory dwelling units are second, self-contained homes on a lot that already holds a house. An accessory dwelling unit has its own entrance, kitchen, bathroom and services, and is legally recognised as a separate dwelling. In Ontario the category covers four physical forms: a detached suite in the rear yard (garden suite or laneway house), an internal suite carved out of a basement or upper floor, a conversion of an attached or detached garage, and a factory-built unit craned onto a prepared foundation. We design and build all four across the 30 municipalities of the Greater Toronto Area under a single contract.
Most of our clients are one of three people. A homeowner adding rental income on a lot they already own. A family moving a parent or an adult child into their own front door rather than a spare bedroom. An owner planning ahead, building the unit now and deciding its use later. All three are buying the same thing underneath: a legal second dwelling that will pass final inspection and can be insured, financed and rented.
What this includes
- Feasibility and lot review before you sign - servicing, setbacks and lot coverage checked against the local by-law
- All four ADU forms built in-house: detached garden suite, laneway house, internal secondary suite, garage conversion
- Bill 23 as-of-right assessment - up to three residential units on most serviced GTA lots, no rezoning application
- Ontario Building Code construction with SB-10/SB-12 energy compliance filed in the permit package
- Conservation authority screening for TRCA, Credit Valley and Oak Ridges Moraine lots before design begins
- Zoning and by-law handling across all 30 GTA municipalities under one contract
- Fixed-scope pricing issued before construction starts, in the $300-$600/sq ft GTA band
- WSIB clearance certificate and $2M general liability supplied on request, re-verified every 90 days
What is possible on a given lot changed with Bill 23, the More Homes Built Faster Act (2022), which requires Ontario municipalities to permit up to three residential units as-of-right on most lots already holding a detached, semi-detached or townhouse dwelling on full municipal services. Before Bill 23 a second dwelling unit typically meant a rezoning application: six to twelve months, expensive, and refusable. The provincial framework is O. Reg. 299/19 on additional residential units, amended November 2024, with O. Reg. 462/24 harmonising municipal by-laws against province-wide garden-suite criteria. Construction is built to the Ontario Building Code, with energy compliance filed under the SB-10 and SB-12 supplementary standards.
Typical detached units run 500 to 600 sq ft. Construction in the Greater Toronto and Hamilton Area runs roughly $200,000 to $350,000 for a unit that size - a figure CEO Sarah Cipkar of Resimate gave CBC News in July 2025 - or $300 to $600 per square foot depending on site access and finish. Permit review takes four to eight weeks, construction four to eight months, and the honest end-to-end range including design and approvals is eight to fourteen months.
Two site conditions decide feasibility before design starts. Since 1 April 2024 an amended Conservation Authorities Act requires TRCA or Credit Valley Conservation sign-off for units inside regulated areas - ravine, valley land, Oak Ridges Moraine or Niagara Escarpment lots carry a real scheduling risk. And servicing capacity, lot coverage and setbacks vary municipality to municipality even under a harmonised provincial rule.
We carry WSIB registration and $2M general liability, and we issue a clearance certificate on request; under the Construction Act and the WSIA an owner is liable for an unregistered contractor's premiums, and the certificate must be re-verified every 90 days.
Accessory Dwelling Units - Permits and Approvals by Municipality
What approval typically costs, and what the lots look like, in the GTA municipalities we build in most.
| Municipality | Typical approval fees | Lot typology |
|---|---|---|
| Toronto | $8,000-$14,000 in permit, development and plan-review fees | Narrow downtown lots with rear public laneways - Toronto has over 300 km of them, more laneway frontage than any other Canadian city. |
| Brampton | $5,500-$10,000 including Brampton registration and Peel charges | Deep newer-subdivision lots, many with an existing unregistered basement apartment that must be brought to Ontario Building Code fire-separation standard. |
| Mississauga | $6,500-$11,000 in City of Mississauga and Region of Peel charges | Large 1970s-90s subdivision lots with attached garages; garage conversions and rear coach houses are both common outcomes. |
| York | $8,000-$14,000 under the City of Toronto fee schedule | Older narrow semi-detached lots on a laneway grid, with frequent shared-driveway conditions that must be resolved before permit. |
| Etobicoke | $8,000-$14,000 under the City of Toronto fee schedule | Split personality - laneway-served lakeshore grid in Mimico and New Toronto, versus large treed lots in The Kingsway where garden suites dominate. |
| Ajax | $7,000-$12,000 including Durham Region charges | Compact 1990s-2000s subdivision lots where the required 1.2 m side-yard construction access sets the maximum module width we can crane in. |
| King | $9,000-$16,500 including York Region and septic charges | Estate and agricultural parcels, many over an acre, on private well and septic with moraine core-area restrictions. |
| North York | $8,000-$14,000 under the City of Toronto fee schedule | Deep post-war bungalow lots, commonly 50 ft × 120 ft, with rear yards large enough for a detached garden suite plus the required 1.5 m separation. |
Fee bands are indicative, drawn from project experience - confirm current tariffs with the municipality before budgeting.
Related Unit Types
Frequently Asked Questions
Everything you need to know about our services.
Full-service accessory dwelling unit design and construction across the GTA - we take a single-family lot from feasibility review through permit approval, build and final occupancy sign-off on one contract. Concretely that means: feasibility and lot review before you commit; design, permit and build under one contract; zoning and by-law handling for all 30 gta municipalities; fixed-scope pricing before construction starts. One contract covers design, permit and construction, so there is no handoff between a designer and a builder halfway through.
Related service: Our ADU services
On a 700 sq ft reference unit our estimate band runs $268,000-$359,500 in Brock up to $281,500-$377,000 in East York - roughly $383 to $402 per square foot. The spread is not a markup: this work involves a new foundation, new servicing and a full building envelope, and the per-municipality difference comes from approval fees, frost depth and snow load. Final pricing follows a site visit.
Related service: Our ADU services
Yes - a building permit is required in every GTA municipality. Bill 23 (More Homes Built Faster Act, 2022) and O. Reg. 299/19 permit up to three residential units as-of-right on most serviced lots, so a rezoning application is usually not needed.
Municipal approval costs range from $5,500-$10,000 including Brampton registration and Peel charges in Brampton to $9,000-$16,000 including Peel Region and septic permit charges in Caledon, quoted separately from construction. Plan review typically takes four to eight weeks.
Related service: ADU Building Permit
All 30 municipalities of the Greater Toronto Area, from Toronto out to Clarington. Each one has its own by-law, fee schedule and review stream, and we file into the local one - the municipal page for your address carries that city's approval band, frost depth and building season.
Related service: Our ADU services
Eight to fourteen months is the honest end-to-end range: design and drawings, four to eight weeks of plan review, then construction. Because this work is a new foundation, new servicing and a full building envelope, the build phase is the part that moves most between projects. Excavation is scheduled inside the local building season, and interior work carries on through winter.
Related service: Our ADU services
Ready to Get Started?
Ready to start your accessory dwelling units project? Send us your address and we will tell you what your lot allows, what it costs and how long the permits take.