Garden suite permits in Ontario: what the province decides, what your city decides, and what you actually submit

Short answer: every garden suite in Ontario needs a municipal building permit, and the process has the same bones everywhere — a zoning check, a complete application with site and grading plans, plan review, a permit, staged inspections, and occupancy. The province sets what a city cannot refuse and the Building Code the suite must meet. The city sets size, height, setbacks, fees, and how long review takes. This guide is the shared skeleton; the nine city guides linked at the end carry the city-specific numbers.

Who decides what

A garden suite permit sits on three layers of law, and knowing which layer a rule comes from tells you whether it can be argued with.

The province sets the floor. The Planning Act stops a zoning by-law from prohibiting one additional residential unit in an ancillary building on most urban residential lots that have a detached, semi-detached or row house (Planning Act s. 35.1(1)). O. Reg. 299/19 says that unit may be occupied by anyone, related to the owner or not, and — as amended by O. Reg. 462/24 — adds standards a by-law cannot go below: the unit "shall be at least 4 metres from another building or structure on the parcel if the other building or structure contains a residential unit" unless the by-law permits less; "up to 45 per cent of the surface of the parcel is permitted to be covered by buildings and structures"; no floor-space-index limit; and minimum lot area cannot be stricter than it would be without the unit (O. Reg. 299/19 ss. 4–5).

The Building Code sets how it is built. Every suite, factory-built or site-built, must meet the Ontario Building Code — now O. Reg. 163/24 — and the city inspects at the stages the Code sets (O. Reg. 163/24). The province's guide to building a modular house is explicit that a factory-built home "still needs a municipal building permit and on-site inspections for the foundation and connections" (Ontario — building a modular house).

The city sets everything in between. Size, height, setbacks, separation from the house, parking, fire access path, trees, fees, and review time are all municipal. That is why the same suite that fits in Richmond Hill fails in Brampton, and why this guide stops at the concepts and hands the numbers to the city guides.

What a complete application contains

The exact forms vary, but across the GTA a garden suite building permit application contains the same things. If any of them is missing, the application is incomplete and the review clock does not start.

1. The provincial application form — the Application for a Permit to Construct or Demolish, with Schedule 1 (designer information) and, where required, a Compliance with Applicable Law form.
2. A survey. Not a sketch. A legal survey of the lot, because every setback is measured from it.
3. A site plan showing the suite's position, every setback, the separation from the house, the path from the street to the suite's door with its width, and any trees near the work.
4. A lot grading and drainage plan. Where the water goes after you have put a roof in the backyard. Several cities require this to be prepared by a professional.
5. Architectural drawings — floor plans, elevations, sections — drawn to the by-law's size and height limits, or a reference to a city pre-approved plan where one fits.
6. Structural, mechanical and plumbing information, including how water, sewer and power reach the suite from the house and whether the existing service has capacity.
7. Tree information where a protected tree is near the work — a declaration at minimum, a permit application where the tree is affected.
8. Any applicable-law approvals that come first: a conservation authority permit on regulated lands, heritage review on a listed property, a minor variance where the design misses a zoning standard.
9. The fee.

Toronto formalises the first step: a Zoning Applicable Law Certificate (ZAP) is part of a complete building permit application, obtained before the permit is filed (Zoning Applicable Law Certificate). Mississauga offers an optional preliminary zoning review that runs in rounds of about 20 business days (preliminary zoning review). Burlington requires a Pre-Building Approval application before the permit (pre-building approval). Different names, same idea: settle zoning before you pay for a permit review.

The sequence, start to finish

Factory production and permitted site work can overlap once the permit is issued. Nothing else in the table can.

What the city controls, in one table

Fees and charges: what is provincial and what is municipal

Development charges. The Development Charges Act exempts one residential unit in an ancillary building on a lot with a detached, semi-detached or row house from development charges, and exempts additional units in existing houses within limits (Development Charges Act s. 2(3.2)–(3.3)). Cities apply that through their own by-laws, and the result is not uniform. Toronto's By-law 845-2025 does not impose development charges on the second, third or fourth unit on a parcel of up to six (By-law 845-2025). Oakville relies on the Act's mandated exemption and notes that education development charges may still apply (Oakville development charges). Mississauga's ARU page says the opposite of what people expect: "Development charges will also apply for additions and garden suites" (Mississauga additional residential units) — while the City's April 2026 incentives table marks second and third units "Exempt as per the Development Charges Act," without reconciling the two. Budget for the charge and confirm in writing. Education development charges, set by school boards, are the ones most often payable regardless: Brampton collects them before the permit is issued (Brampton garden suite process), Whitby states they apply to all detached ADUs (Whitby additional dwelling units), and Burlington says they "may apply to detached Additional Residential Units" (Burlington ARU incentive program).

Permit fees are entirely municipal. Mississauga's ARU page states that "building permit fees are refunded when you're building or legalizing ARUs," by cheque after the ARU is constructed and inspected, and that "garden suites have a fee of $81.90, plus HST, for a new address" (Mississauga ARU page, above). Toronto's 2026 schedule sets a minimum permit fee of $214.79, $56.33 per new residential unit, and a Service Index of $18.56 per m² for houses — $15.75 per m² for permits on certified plans (Toronto building permit fees). Brampton's stack — a $530 planning review fee, a $5,000 security deposit, a $200 registration fee and a $2,004.10 permit fee — is the heaviest in the GTA (Brampton process page, above). Burlington's fee waivers have ended: its ARU Incentive Program "closed October 1, 2025" and municipal fee waivers were "available until Dec. 31, 2025" (Burlington incentive page, above).

Registration is a separate municipal step in a growing number of cities — Milton, Pickering, Whitby, Markham (fire registration), Caledon — usually after the final inspection, sometimes with its own fee. The city guides list each.

Incentives exist and expire. Whitby reimburses permit and registration fees and education charges for detached ADUs permitted on or after 1 April 2024 and registered by 31 March 2027 (Whitby ADU page, above). Ajax pays a grant per new unit after the permit is closed (Ajax ADU grants). Caledon's Gentle Density CIP pays grants at permit issuance for permits issued on or after 25 November 2025 (Caledon housing). Brampton's garden suite grant closed on 21 July 2025 (Brampton garden suites). Programs change; the financing guide tracks them and dates every claim.

Timelines: only the ones a city publishes

We state a review time only where the city publishes one. Toronto's House Stream "also includes ancillary buildings such as garden suites and laneway suites," and "complete applications are reviewed within 10 business days" (building permit review streams). Mississauga: "If your application is complete, the first review may take 15 business days," and resubmissions "may result in delays of two weeks or more" (Mississauga ARU page, above). Burlington issues the permit within 10 business days once the application is complete, after a Pre-Building Approval of about 3–6 weeks (Burlington steps to build an ARU). Oshawa says processing times "vary depending on the type of construction" (Oshawa building permits).

Two things sit outside the permit clock and routinely take longer than it. A Toronto street occupation permit for a crane or truck takes about 12 weeks (street occupation permit). A minor variance through a Committee of Adjustment adds months in any city. Both should be started the day the design is fixed, not the day the permit is issued.

Where permits go wrong

Incomplete applications. The review clock starts when the file is complete. A missing grading plan or an unsigned Schedule 1 does not get a comment; it gets a return. Toronto states it directly: "There is no time frame for review of incomplete permit applications" (review streams page, above).

Trees. "Starting September 1, 2026, changes to Toronto's Tree Bylaws come into effect," including stronger protections for existing trees; injuring or removing a protected tree needs a permit (Toronto tree and ravine protection permits). Trees stop more backyard projects than zoning does, and they are the thing a lot check from the street cannot see.

Conservation authorities. Lots regulated by TRCA, Credit Valley Conservation, Conservation Halton or CLOCA need that authority's permit before the building permit, and the building permit will not proceed without it (TRCA planning permits). A creek at the back of the lot is a regulated area.

Fire access. The path from the street to the suite's door has a minimum width and height and a maximum length, and it is rarely a variance item. Toronto's published options are "a maximum of 45 metres in length measured from the public street to the entry of the Garden Suite," or "a maximum of 90 metres … along with at least one additional fire-safety measure, acceptable to the City of Toronto"; the City's options stop at 90 metres (Toronto fire department access to a new garden suite).

Servicing capacity. A suite shares the house's water service unless the city requires a separate one. Richmond Hill does (Richmond Hill ARU page). Where it shares, the existing pipe has to have capacity, and Mississauga asks for a Water Service Pipe Sizing Form to prove it (Mississauga ARU page, above).

Building without one. Toronto treats a structure built without a permit as a new building, reviewed against today's rules (Toronto garden suites).

Pre-approved plans do not skip the permit

Toronto, Mississauga, Richmond Hill, Caledon, Pickering and Whitby all publish pre-approved or pre-reviewed designs. Every one of them says the same thing: the design has been reviewed; the permit for your lot has not. Toronto's plans skip re-review of the building design, and you still apply for a building permit with the site, grading and fire-access work reviewed against your property (Toronto pre-approved plans). What a pre-approved plan saves is design time and, in some cities, a fee tier. What it does not save is a single step of this guide. See pre-approved garden suite plans for which ones we build.

Your city's rules

The numbers — size, height, setbacks, fees, timelines — live on the city guides: Toronto garden and laneway suite permits · Mississauga garden suite permits · Etobicoke garden suite permits · Brampton garden suite permits · Oakville garden suite permits · Burlington garden suite permits · Milton garden suite permits · Hamilton garden suite permits · Vaughan garden suite permits · Markham garden suite permits.

The step-by-step from the first lot check to the day you get keys is in how the process works, from feasibility to occupancy. The concepts behind every setback and height figure are in garden suite setback and size rules.

What you will see from us

We run the file. That means we pull the survey, confirm zoning before design, prepare the site and grading package, file a complete application, and book every inspection. You pick the plan and the finishes. We will tell you which stage the file is at and what the city has said, in the city's words, not ours. A permit is a sequence, not a promise, and we describe it that way.

Check if your lot qualifies.

Disclaimer: Figures cited are market estimates provided for information only and are not a quote. Municipal rules, fees, and programs change — always verify current requirements with your local authority. Modular X provides exact pricing only after a site-specific feasibility review.