Can I build a garden suite on well and septic?

It depends on the municipality. Burlington does not permit ARUs on private water or sewer services. Oakville requires municipal water and sewage south of Highway 407. Milton permits up to two ARUs without full services instead of three. Toronto, Mississauga and Brampton do not clearly publish a servicing restriction for ARUs.

Do I still need a building permit if I use a pre-approved plan?

Yes. Toronto states directly that a building permit is still required with a pre-approved plan. Pre-approval covers the building design, not the zoning on your particular lot.

Why does every municipality use a different word?

Ontario legislation uses additional residential unit. Toronto separates garden suite from laneway suite based on whether the lot abuts a public lane. Brampton and Mississauga call the detached form a garden suite. Oakville says additional residential unit in zoning and accessory apartment in building permits. Milton says ARU in planning and ADU in permits. The building is the same; the vocabulary is local.

Did Toronto's laneway suite separation distance change?

Yes. Until 24 July 2025 a laneway suite had to sit 5.0 m from the main house if it was no taller than 4.0 m. By-law 847-2025 reduced that to 4.0 m, which is the same figure that already applied to garden suites. Anything published before that date — including the City's own online office consolidation of By-law 569-2013, which has not caught up — still shows 5.0 m. Check the enacted by-law, not the consolidation.

Garden & Laneway Suite Rules Across the GTA: A 2026 Municipal Comparison

Six GTA municipalities, six different rule sets, and no two use the same vocabulary. This table compares what each one publishes for a detached additional residential unit — the building most people call a garden suite. Every figure links to the municipal source. Where a municipality does not publish a value, we say so rather than guessing.

Municipal sources last verified 29 August 2026. Zoning by-laws and fee schedules change — confirm with the municipality before designing to any figure on this page.

The comparison table

Scroll the table sideways on a phone. Rows read across the six municipalities; the phrase "Not clearly published" means exactly that — the municipality does not publish the value, and we have not substituted one from a neighbour.

Requirement	Toronto	Mississauga	Brampton	Oakville	Milton	Burlington
Municipal term	Garden suite / laneway suite	ARU (detached = garden suite)	ARU (detached = garden suite)	Additional residential unit (detached)	ARU (ADU in permit documents)	ARU (additional residential unit – detached)
Detached permitted	Yes	Yes	Yes	Yes	Yes, except detached not allowed in the Niagara Escarpment Plan area	Yes
Max ARUs per lot	One garden suite or one laneway suite	2 (max 1 detached)	2 (max 1 detached)	2 (max 1 detached)	3 with full municipal services, 2 without; only 1 may be detached	3; only 1 may be in an accessory building
Servicing tier affects unit count	Not clearly published	Not clearly published	Not clearly published	Unit cap does not vary, but municipal water and sewer are required south of Highway 407	Yes — 3 ARUs requires municipal water and sewer	Not permitted on private well, cistern or septic
Rear setback	Garden 1.5 m; laneway 0.0 m where the rear lot line does not abut a street or lane and has no openings, otherwise 1.0 m	1.8 m	2.5 m	0.6 m in a rear or flankage yard where separation from the dwelling is at least 2.0 m, otherwise the same yard as the dwelling	Not clearly published	1.2 m, increasing to 3 m for the portion above 4.6 m (peaked) or 3.5 m (flat)
Side setback	Garden 1.5 m; laneway 0.0 m with no openings, 1.5 m above 4.0 m height beside residential zones, otherwise 1.0 m	0.6 m one storey, 1.8 m two storey (interior); 2.5 m one storey, 4.5 m two storey (street-facing)	1.8 m interior	As rear	Not clearly published	1.2 m, increasing to 3 m above the same height thresholds
Separation from main dwelling	Garden and laneway are now the same: 4.0 m if the suite is 4.0 m or less in height, 7.5 m if taller. Exception: in the East Toronto area bounded by Coxwell Avenue/Coxwell Boulevard/Massey Creek, the Don River/Sunrise Avenue, Victoria Park Avenue/Nursewood Park and Lake Ontario, a garden suite taller than 4.0 m needs only 5.0 m.	1.2 m — reached indirectly via the detached garage standard; confirm with the City	3 m	2.0 m, as the condition for the reduced 0.6 m yard	Not clearly published	4 m
Maximum height	4.0 m if less than 7.5 m from the main building, 6.3 m if 7.5 m or more; laneway also capped at two storeys	Sloped roof 4.6 m one storey, 6.8 m two storey; flat roof 3.0 m and 5.8 m	4.5 m in standard residential zones; 7.5 m in Hamlet, Estate and Agricultural zones — or the height of the principal dwelling, whichever is less	4.0 m, reduced to 2.5 m within 3.5 m of a flankage lot line	Not clearly published	7 m peaked roof, 6 m flat roof
Maximum floor area	Garden suite 120 m² total, 60 m² single storey	55 m² on lots up to 550 m² (single storey only); 10% of lot area to a maximum of 100 m² on larger lots	35 m² in standard residential zones; 80 m² in Hamlet, Estate and Agricultural zones	Accessory building coverage capped at the greater of 5% of lot area or 42 m²	Not clearly published	80 m², or 15% of lot area in the LN5 and LN6 zones. Lot coverage may be the greater of the zone requirement or 45%.
Parking required	None; two bicycle spaces	None additional	None for one ARU; one additional space where there is more than one	One additional space	Not clearly published	Zero for the first ARU; one for the second or third
Fire access path	0.9 m × 2.1 m sprinklered, 1.0 m × 2.1 m non-sprinklered (garden); 0.9 m × 2.1 m (laneway)	1.2 m wide × 2.1 m high	1.2 m pedestrian path — published as a path of travel, not a fire route	Not clearly published	1.2 m wide × 2.1 m high	Not clearly published
Max travel distance from street	45 m; 45–90 m permitted with at least one additional fire-safety measure accepted by the City	45 m	Not clearly published	Not clearly published	Not clearly published	Not clearly published
Registration	Not clearly published	Mandatory for second units, no fee; whether a detached garden suite must register is not clearly published	Mandatory under By-law 157-2022. The City publishes two different fees — $200 and $530 — on different pages	Not required; a Zoning Certificate of Occupancy is required instead	Mandatory since 1 April 2025 — $340 per ARU	Not clearly published
Pre-approved plans	Yes — 8 base designs in 24 fire-access variants; a building permit is still required	Yes — Studio 40 m² (430 sq ft) and One-Bedroom 55 m² (600 sq ft)	None published	None published	None published	None published
Development charges	Exempt for second, third and fourth units; otherwise a dedicated programme defers them for 20 years from permit issuance	The City states development charges "will also apply for additions and garden suites" — confirm for a specific project	Municipally exempt; Education Development Charges still payable	Exempt from Town and Regional charges; education charges may apply	Exempt	Exempt; Education Development Charges may still apply
Other notable requirement	Laneway suites need a lot line abutting a lane for at least 3.5 m; max length 10 m, width 8 m	Building permit fees are refunded after construction and final inspections	New Zoning By-law 14-2026 is under appeal; both it and 270-2004 apply, most restrictive prevailing	By-law 2026-088, adopted 15 June 2026, introduces minimum yards for ARUs — figures above predate it	Detached ARUs not permitted in the Niagara Escarpment Plan area	A Pre-Building Approval application is required before the building permit; review takes 4–6 weeks

City-by-city detail sits on the market pages — the Toronto rules are unpacked on our Toronto garden suite page, the lane-abutting variant on the laneway suite page, and the incentive stack west of the city on the Mississauga page.

Where the rules diverge most

Floor area is the biggest practical gap. Brampton caps a garden suite at 35 m² in standard residential zones while Toronto allows 120 m² and Burlington 80 m². The same design is legal in one municipality and impossible two towns over.

Separation from the house is the second. It ranges from 1.2 m in Mississauga to 7.5 m in Toronto, where a suite taller than 4.0 m must generally stand 7.5 m clear of the house — with a carve-out in East Toronto, where 5.0 m is enough. On a shallow lot that single number decides whether anything fits.

Only Toronto and Mississauga publish pre-approved plans, and only Toronto publishes a development charge deferral. Everywhere else the soft costs are quoted project by project.

What we could not verify

Milton publishes its detached ARU permissions clearly but its dimensional standards sit in Section 4.10 of Comprehensive Zoning By-law 016-2014, which we could not retrieve in full. Brampton's registration fee appears as $200 in the registration by-law and permit package and as $530 on the City's garden suite page. Brampton's new Zoning By-law 14-2026 and Oakville's By-law 2026-088 both post-date the consolidations available to us and both touch ARU standards directly. Treat every figure here as a starting point and confirm with the municipality before designing to it. We update this page when municipal sources change.

If you would rather skip the by-law reading, the fastest way to find out which of these numbers actually bind is to run your address through the lot check.

FAQs

On floor area, Toronto — 120 m² against Brampton's 35 m² in standard residential zones. On unit count, Milton and Burlington both permit up to three ARUs, though Milton drops to two without full municipal services. There is no single most permissive municipality; it depends which constraint binds on your lot.

Keep reading

Guide

Garden Suite Cost in Mississauga (2026)

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Guide

Garden & Laneway Suite Cost in Toronto (2026)

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Guide

Mississauga Garden Suite Permits, Step-by-Step

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Guide

Modular vs Site-Built Garden Suites

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Every figure below is drawn from an official municipal source. Where a municipality does not publish a value, this page says so rather than estimating.

Municipal sources

Sources

Municipal rules, fees, and programs change. Confirm current requirements with the city at application. Modular X provides exact pricing only after a site-specific feasibility review.

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.