Garden Suite Rules by City 71 Ontario municipalities, one table
The province sets the floor. Your town sets the numbers. We pulled size, height, terminology and grants for 71 municipalities from their own pages and by-laws. The spread is wide: from 35 m² in Brampton’s residential zones to no published cap at all in North Bay.
At a glance
Provincial rules apply to urban residential land with full municipal services. Rural and septic lots follow the township by-law.
On an urban Ontario lot with town water and sewer, the province lets you have up to three units, one of them in the backyard. It guarantees at least 45% lot coverage and caps separation rules at 4 m, but sets no size limit. Each town sets its own size, height and setbacks, from 35 m² in Brampton to no cap in North Bay.
One Province, Seventy-One Rulebooks
Ontario did the big move in 2022 with Bill 23: additional units are allowed as of right on most urban lots. Then every municipality wrote its own numbers, in its own words, in its own zoning by-law. That is why your neighbour’s cousin in Mississauga is no help to you in Tiny Township.
Below you get the provincial baseline first, then a translation table for the words towns use, then every municipality we have checked, grouped by region with a link to our local page. If you just want your own town, the Rules Checker is faster.
We are builders. We have built more than 300 custom homes since 1979, and we read by-laws the way an inspector does: looking for the line that stops the job. Where a town does not publish a number, the table says so. We do not fill gaps with guesses.
What Ontario Guarantees Before Your Town Says a Word
These apply to a parcel of urban residential land with full municipal water and sewer. Rural lots and lots on septic are not covered by the guarantees below.
Three units as of right
Under the Planning Act as changed by Bill 23 (2022), a serviced urban lot with a detached, semi or townhouse can have up to three units: three in the main building, or two in the main building and one in an ancillary building such as a garden suite.
45% lot coverage, at least
O. Reg. 299/19, as amended in November 2024 (O. Reg. 462/24), says a town must allow at least 45% lot coverage for all buildings on a lot with additional units. Setbacks can still control where things go.
No FSI cap, no angular planes
Floor space index limits and angular plane rules in a zoning by-law do not apply to lots with additional units under the amended regulation. That removed two of the quiet killers of backyard suites in older cities.
4 m separation cap
A town cannot require more than 4 m between a building with an additional unit and another residential building on the lot. Rules like Toronto’s 7.5 m separation for taller suites are exactly what this caps, so ask your city how it is applying the change.
No special minimum lot size
Minimum lot size rules aimed only at lots with additional units are overridden. A lot that is big enough for a house is big enough for the additional units, as far as minimum lot area goes.
Parking and DCs
Towns cannot demand more than one parking space per additional unit, and the Development Charges Act exempts the second and third units on a lot with a house. Confirm education charges and local wording with your town.
Last checked October 2026 · Source: ERO 019-9210 decision (Dec 4, 2024) · O. Reg. 462/24 amending O. Reg. 299/19
What the province does not set: maximum size, maximum height, side and rear setbacks, where on the lot the suite can go, and whether a rural lot on septic qualifies. Those are all local. That is why the table below exists.
Same Building, Eight Different Names
Search the wrong word on a town website and you get nothing. Here is which word each town uses, from our data.
| Term | Who uses it | What it usually means |
|---|---|---|
| Garden suite | Toronto, Mississauga, Brampton | A permanent detached unit in the back yard. In Toronto, a laneway suite if the lot backs onto a public lane. |
| Garden suite (temporary) | Essa, Ramara, Severn, Tay, Tiny, Orillia, Cavan Monaghan, Selwyn, Guelph/Eramosa, Wellington North, Mapleton, North Dumfries, Clarington | A removable unit approved by a temporary use by-law, usually rural, often for a family member, with a removal agreement. |
| Additional residential unit (ARU) | Barrie, Collingwood, Essa, New Tecumseth, Ramara, Severn, Springwater, Burlington, Milton, Halton Hills, Caledon, Richmond Hill, Vaughan, Newmarket, Kingston, London, Waterloo, Cambridge, Lakeshore, Peterborough, Kawartha Lakes, Puslinch, Centre Wellington, The Blue Mountains, Owen Sound, Muskoka, Bruce | The provincial term. Covers basement, attached and detached units. Newmarket shortens it to DARU for the detached kind. |
| Additional dwelling unit (ADU) | Hamilton, Kitchener, Guelph, Oakville, Whitby, Pickering, Clarington, Niagara Falls, Windsor, North Bay, Greater Sudbury, Thunder Bay, Sault Ste. Marie, Orillia, Tiny, Penetanguishene | Same idea as ARU. Kitchener calls the backyard kind a backyard home. |
| Accessory dwelling unit (ADU) | St. Catharines, Welland, Innisfil, Bradford West Gwillimbury, Clearview, Tay, Wasaga Beach | Same initials, different word. Some older by-laws using this term still limit or ban detached units, so read the section. |
| Coach house | Ottawa (official term); Waterloo for the detached kind | A detached unit in an accessory building. Ottawa’s rules are in By-law 2008-250 s. 133. |
| Second unit / secondary suite | Selwyn, Midland, Markham; Kingston formerly said second residential unit | Older wording, usually from before Bill 23. Often written with basement apartments in mind. |
| Accessory apartment / ancillary unit | Oshawa, Oro-Medonte (accessory apartment); Aurora (ancillary unit) | Check carefully whether a detached building is allowed at all, or only a unit inside the house. |
Last checked October 2026 · Source: municipal pages and by-laws linked in the table below
The full glossary, with granny flats, granny pods, bunkies and tiny homes, is on our garden suite vs ARU vs ADU vs coach house page.
Garden Suite Rules by City: 71 Municipalities by Region
Size and height are the detached unit rules where a town separates them. Money is what we found listed in October 2026, not a promise it is still open.
| Municipality | Term used | Max size | Max height | Money available | Our page |
|---|---|---|---|---|---|
| Toronto · 1 municipality · Read the Toronto page | |||||
| Toronto | garden suite (laneway suite where the lot abuts a public lane) | 60 m² GFA one storey; 120 m² GFA two storey; must be less than main house GFA; suite basement counts | 4.0 m if less than 7.5 m from main house; 6.3 m if 7.5 m or more from main house (from average grade) | None found | Guide |
| Peel Region · 3 municipalities · Read the Peel Region page | |||||
| Mississauga | garden suite (detached ARU in By-law 0174-2023) | Lots 550 m² or less: 55 m², one storey only; larger lots scale with lot area (10% of lot area to a cap – confirm) … | 1 storey 4.6 m sloped / 3.0 m flat; 2 storey 6.8 m sloped / 5.8 m flat; not above main dwelling ridge | Permit fee refund; no grants for 2nd/3rd units; 4th unit may qualify via Affordable Rental CIP | Guide |
| Brampton | garden suite (ARU in a separate building) | 35 m² in residential zones; 80 m² in Hamlet, Estate, Agricultural zones | Lesser of principal dwelling height or 4.5 m (7.5 m in Hamlet, Estate, Agricultural) | Garden Suite Grant Program closed July 21, 2025; none found | Guide |
| Caledon | detached additional residential unit | R zones: not more than ground floor area of main dwelling and not more than 80 m²; RE/RR and A1-A3: 110 m² GFA | R zones 4.5 m; RE/RR and A1-A3: no taller than main dwelling or zone limit, whichever is less | None found | Guide |
| York Region · 5 municipalities · Read the York Region page | |||||
| Markham | secondary suite / additional dwelling unit (coach house or garden … | Not published – check zoning by-law 2024-19 | Not published – check zoning by-law 2024-19 | None found | Guide |
| Vaughan | Additional Residential Unit in an Accessory Building (web: secondary … | ARU floor area not more than GFA of principal dwelling unit | not in ARU section – check zoning by-law | None found | Guide |
| Richmond Hill | Additional Residential Unit in an Accessory Residential Building | building coverage max 80.0 m² incl. integral garage | 2 storeys; main walls 6.0 m; 7.5 m to highest point of roof | None found | Guide |
| Newmarket | Detached Additional Residential Unit (DARU) | 1 storey: lesser of 10% of lot area or 75 m²; 2 storey or above garage: lesser of 10% of lot area or 100 m² | lesser of main house height or: 1 storey 5.5 m pitched / 3.5 m flat … | None found | Guide |
| Aurora | Ancillary Unit (Registration By-law 6660-24) … | Not published – check zoning by-law 6000-17 | Not published – check zoning by-law 6000-17 | None found | Guide |
| Halton Region · 4 municipalities · Read the Halton Region page | |||||
| Burlington | Additional Residential Unit (detached ARU) … | 80 m² floor area; 15% of lot area in LN5 and LN6 zones | 7 m peaked roof / 6 m flat roof | ARU Incentive Program closed Oct 1, 2025 (was up to $95,000 forgivable loan detached affordable, $70,000 interior, $15,000 legalization … | Guide |
| Oakville | additional dwelling unit (detached additional dwelling unit) | lot coverage greater of 5% or 42.0 m² (Table 6.5.3); counts toward lot coverage in Residential Low zones | 4.0 m from grade | None found | Guide |
| Milton | Additional Residential Unit (additional dwelling unit in zoning text) | draft by-law: lesser of 10% of lot area or 110 m² GFA – confirm enacted text | draft: 4.3 m gable/hip/gambrel/mansard; 3.5 m flat | None found | Guide |
| Halton Hills | Additional Residential Unit | ARU lesser of 40% of floor area or 110 m², or entire basement (fully serviced lots) | Not published – check By-law 2010-0050 | None found | Guide |
| Durham Region · 5 municipalities · Read the Durham Region page | |||||
| Oshawa | accessory apartment / accessory dwelling (two-unit house) | most restrictive of 8% of lot area, 50% of house lot coverage, or 60 m² ground floor area | 14 ft 9 in roof peak from grade in most cases | None found | Guide |
| Whitby | Additional Dwelling Unit (detached ADU) | 75 m² GFA (By-laws 8141-24 / 8143-24) | 4.5 m Residential zones; 5.5 m other zones | HAF fee reimbursement (permit, registration inspection, curb cut, below-grade entrance, education DCs on detached ADUs): permit issued … | Guide |
| Pickering | Additional Dwelling Unit | Not published – check zoning by-law | Not published – check zoning by-law | None found | Guide |
| Ajax | additional residential unit (provincial term) – confirm Town wording | Not published – check zoning by-law | Not published – check zoning by-law | None found | Guide |
| Clarington | additional dwelling unit; garden suite (temporary, rural) | Smaller than the main house floor area | 5.25 m Urban Residential; 6.5 m Agricultural / Rural Residential | None found | Guide |
| Hamilton · 1 municipality · Read the Hamilton page | |||||
| Hamilton | Additional Dwelling Unit – Detached (ADU) … | Urban: lesser of 75 m² or principal dwelling GFA (By-law 05-200 s. 4.33.2, By-law 22-132); Rural: not more than principal dwelling GFA | Urban 6.0 m (By-law 22-132); Rural 6.0 m (By-law 24-039) | ADU and Multi-Plex Housing Incentive Program (HAF): grant 70% of eligible costs up to $40,000 per unit, $240,000 per site … | Guide |
| Niagara · 3 municipalities · Read the Niagara page | |||||
| St. Catharines | accessory dwelling unit (ADU); detached / exterior ADU | Not published – check zoning by-law 2013-283 (pre-approved designs 37-80 m²) | Not published – check zoning by-law 2013-283 (a 2025 Committee of Adjustment notice cites 6 m for detached … | CIP ADU Grant up to 70% of costs, max $80,000 exterior / $40,000 interior – Funding depleted for 2025; no 2026 intake posted, ask the City | Guide |
| Niagara Falls | additional dwelling unit (ADU) | no ADU cap; all accessory buildings incl. detached ADU limited to 93 m² lot coverage | urban: walls 4.5 m, pitched roof 6 m; rural: walls 5.5 m, pitched roof 7 m | None found | Guide |
| Welland | accessory dwelling unit | Not published – check zoning by-law 2017-117 s. 5.2 | Not published – check zoning by-law 2017-117 s. 5.2 | None found | Guide |
| Waterloo Region · 4 municipalities · Read the Waterloo Region page | |||||
| Kitchener | ADU (additional dwelling unit); detached = backyard home | 80 m² building footprint; accessory buildings typically 15% lot coverage | 4.5 m; 6.0 m if main house over 9.1 m | ADU Grant (DCs) first-come while HAF funding lasts, priority permits by Oct 31, 2026 … | Guide |
| Waterloo | ARU (additional residential unit); detached = coach house | Not published – check zoning by-law (2018-050) | 6 m | City ARU Grant: detached 50% of costs max $30,000 (interior max $20,000), 5-yr affordable rent at or below 80% AMR, first-come while HAF … | Guide |
| Cambridge | ARU (additional residential unit) | Not published – check zoning by-law 26-007 s. 4.19 | Not published – check zoning by-law 26-007 s. 4.19 | ARU Financial Assistance Program: one-time grant up to $10,000 (since Nov 1, 2024; no end date published) … | Guide |
| North Dumfries | garden suite (temporary, portable); coach house … | coach house subordinate in size to main dwelling; not published – check zoning by-law | Not published – check zoning by-law | Region of Waterloo Secondary Suites forgivable loan up to $25,000 may apply | Guide |
| Guelph and Wellington County · 8 municipalities · Read the Guelph and Wellington County page | |||||
| Guelph | additional dwelling unit (ADU) | 80 m² (861 sq ft) per detached ADU; floorplate up to 90 m² for building with two ADUs | 6.1 m to roof midpoint | Affordable Housing CIP grant (min 15 years affordable) | Guide |
| Puslinch | additional residential unit (ARU) | 45% of principal dwelling floor area, max 130 m² (1,399 sq ft) | varies – check zoning by-law | ARU Grant Program: $10,000-$15,000 per ARU, max $20,000 per property; rent max 80% of CMHC AMR for calculated period; no STR … | Guide |
| Centre Wellington | additional residential unit (ARU) | detached ARU no larger than principal dwelling, max 186 m² (agricultural lots) | 8.0 m accessory building | None found | Guide |
| Guelph/Eramosa | additional residential unit (ARU); garden suite = temporary use | 2022 proposal: ARU 45% of main dwelling GFA up to 115 m² (confirm adopted) … | 2022 proposal: 5 m for whole-building ARU | None found | Guide |
| Wellington North | additional dwelling unit; garden suite = temporary portable unit | Not published – check zoning by-law | Not published – check zoning by-law | None found | Guide |
| Mapleton | additional residential unit; garden suite = temporary portable unit | Not published – check zoning by-law | Not published – check zoning by-law | None found | Guide |
| Erin | garden suite / additional residential unit | garden suite cap 74.9 m² per 2015 Guelph/Eramosa report (old – confirm with Town) | Not published – check zoning by-law | None found | Guide |
| Minto | Not published – check with Town | Not published – check zoning by-law | Not published – check zoning by-law | None found | Guide |
| London · 1 municipality · Read the London page | |||||
| London | Additional Residential Unit (detached ARU) | ARU GFA max 80% of primary dwelling GFA (Interim Control By-law CP-1600-300, until appeals to Mar 3, 2026 amendment … | Not published – check Zoning By-law Z.-1 s.4.37 (general accessory 4.0 m limit does not apply to detached … | ARU Construction Grants ($20,000 / $45,000 affordable / $45,000 Indigenous; permits Apr 29 – Sep 7, 2026) closed, funds allocated … | Guide |
| Windsor-Essex · 2 municipalities · Read the Windsor-Essex page | |||||
| Windsor | ADU (additional dwelling unit) | Not published – check zoning by-law 8600 s. 5.99.80 | 8 m with roof slope 20 degrees or more; 6 m if flatter (variance to 8 m possible) … | None found | Guide |
| Lakeshore | ARU (additional residential unit); agricultural ARU | 50% of primary dwelling, max 120 m² GFA (agricultural 140 m²) | 6.5 m, not taller than primary (agricultural 7.5 m) | None found | Guide |
| Ottawa · 1 municipality · Read the Ottawa page | |||||
| Ottawa | coach house (additional dwelling unit in an accessory structure) | Footprint lesser of 40% of principal dwelling footprint (or 50 m² if dwelling 125 m² or less), 40% of yard, and 80 m² … | Rural-type zones: lesser of main house or 4.5 m (6.1 m with parking garage) … | None found | Guide |
| Kingston · 1 municipality · Read the Kingston page | |||||
| Kingston | ARU (additional residential unit); formerly second residential unit | GFA equal to or less than principal dwelling | Not published – check zoning by-law 2022-62 (2019 guide: accessory height of the zone, 4.5/4.6/5 m) | Detached ARU forgivable loan lesser of 50% or $40,000 (5-yr rent at or below 90% AMR); Accessibility grant $5,000 … | Guide |
| Peterborough and the Kawarthas · 4 municipalities · Read the Peterborough and the Kawarthas page | |||||
| Peterborough | additional residential unit (ARU) | smaller than principal unit; max 2 bedrooms | 4.3 m | Missing Middle CIP (in effect Jan 2026): building permit fee rebate 100% up to $5,000 … | Guide |
| Cavan Monaghan | garden suite (temporary use) | min 50 m²; max 100 m² or 40% of dwelling GFA | 5.0 m, one storey | None found | Guide |
| Selwyn | second unit; garden suite = temporary use | 60% of principal dwelling footprint (A, RU); 40% (RR, R1, R2) | not above principal structure; one storey in R1/R2; 8 m or 2 storeys over detached garage in A, RU, RR | None found | Guide |
| Kawartha Lakes | additional residential unit (ARU) | equal to or less than primary unit floor area | up to 10 m if ARU on upper storey of accessory building | None found | Guide |
| Simcoe County and Georgian Bay · 18 municipalities · Read the Simcoe County and Georgian Bay page | |||||
| Barrie | Additional Residential Unit (ARU); detached ARU / coach house | Zone standard – Zoning By-law 2009-141 s. 5.2.9 (R1 to RM2-TH) or 14.5.2 (R5, NMU); City page gives no number | Zone standard – Zoning By-law s. 5.2.9; check with City | County up to $50,000 forgivable + Barrie Bonus $15,000 + 2026 permit fee cut 50% | Guide |
| Orillia | Additional Dwelling Unit (ADU); garden suite = temporary use | By lot area: 75 m² (lot up to 460 m²), 100 m² (460-1,000 m²), 140 m² (1,000 m²+), porches and decks included; each unit max 75 m² | 6.5 m pitched roof; 5.0 m flat or mansard; no rooftop patio | County up to $50,000 forgivable; City affordable housing incentives case by case | Guide |
| Adjala-Tosorontio | Additional residential unit / garden suite (temporary use) | Not published – check zoning by-law | Not published – check zoning by-law | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Bradford West Gwillimbury | Accessory Dwelling Unit (ADU) | ADU GFA cannot exceed 45% of the GFA of the main building (Town ADU page) | Not published – check zoning by-law | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Clearview | Accessory Dwelling Unit (ADU); ARU in new draft by-law | 111 m² habitable living space, basement counts (s. 2.5.1) | Zone provisions – no ADU-specific height (check zone) | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Collingwood | Additional Residential Unit (ARU) | No floor area cap stated in Town summary – check zoning by-law | 7.5 m or height of main building, whichever is less | County up to $50,000 forgivable + Town Rapid ARU grants up to $15,000 | Guide |
| Essa | Additional Residential Unit (ARU); garden suite = temporary use | ARU: check ARU Guide / zoning by-law. Garden suite: must be smaller than the house | Not published – check zoning by-law | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Innisfil | Accessory Dwelling Unit (ADU) | 50% of principal dwelling GFA, max 100 m² (By-law 080-13 s. 3.5, as amended by 043-21; shoreline lots use the Community Planning Permit System) | Height of the house or 6 m, whichever is less | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Midland | Additional Residential Unit / second unit | Zoning By-law 2004-90 s. 3.39 (Second Units) – check with Planning (free Planning First Zoning Certificate) | Not published – check zoning by-law | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| New Tecumseth | Additional Residential Unit (ARU) | Max 50% of principal building GFA and 80 m² (Zoning By-law 2021-128 s. 2.1.1 b) iv) | 6.5 m and not taller than principal dwelling (s. 2.1.1 b) vi) | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Oro-Medonte | Accessory apartment (current by-law text) … | Accessory apartment 50 to 70 m²; house must exceed 110 m² (s. 5.4) | Detached accessory buildings 4.5 m (s. 5.1.4) | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Penetanguishene | Additional Dwelling Unit (ADU); garden suite | Not published – check zoning by-law | Not published – check zoning by-law | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Ramara | Additional Residential Unit (ARU); garden suite = temporary use | ARU: less than principal dwelling GFA; SR zone detached: less than 50% of principal GFA. Garden suite: 92.9 m² GFA max | Accessory building with ARU up to 10.0 m (s. 2.(1)(7)); garden suite one storey, 4.5 m | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Severn | Additional Residential Unit (ARU); garden suite = temporary use | Lesser of 75% of principal building floor area or 110.0 m² | 5 m (one storey); 8 m if ARU in a half or second storey; not taller than principal dwelling | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Springwater | Additional Residential Unit (ARU) | 40% of primary dwelling GFA, capped by zone accessory floor area or a stated maximum (Township page shows 115 / 1,238 … | Max 2 storeys, not above primary dwelling, max 4.5 m (s. 3.48.3(c)) | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Tay | Accessory Dwelling Unit (ADU); garden suite = temporary use | By lot area: 56 m² (up to 0.20 ha), 74 m² (0.24-0.4 ha), 111 m² (over 0.41 ha); min 37 m² outside full-service areas | 4 m single storey; 6 m total if above a detached accessory structure | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Tiny | Additional Dwelling Unit (ADU); garden suite counts as an ADU … | Detached: 45% of principal dwelling GFA (s. 2.2.3 b) | General accessory building max 5.0 m (s. 2.1.3) – confirm it applies | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Wasaga Beach | Accessory Dwelling Unit (ADU) | Attached ADU 37 m² min, max 45% of main dwelling GFA (s. 3.28.2). By-law 2003-60 s. 3.28.1.5 still says no detached ADU without a temporary use by-law – ask the Town how it applies this after Bill 23 | Detached accessory buildings 5 m to ridge (3.5 m flat roof), one storey | County Secondary Suites Program: up to $50,000 forgivable over 15 years (rent limits) | Guide |
| Cottage Country (Muskoka, Grey, Bruce, Haliburton) · 6 municipalities · Read the Cottage Country (Muskoka, Grey, Bruce, Haliburton) page | |||||
| Muskoka (District) | additional residential unit (ARU) – zoning set by each area … | Not published – check zoning by-law | Not published – check zoning by-law | MAHIP ARU stream: $40,000 (10 years affordable) or $50,000 (15 years affordable); 2027 window open until Jan 8, 2027 | Guide |
| The Blue Mountains | additional residential unit (ARU) | greater of 50% of primary unit or 100 m²; max 2 bedrooms | 5 m; 8 m if above another accessory use | None found | Guide |
| Owen Sound | additional residential unit (ARU) | per underlying zone | per underlying zone | None found | Guide |
| Grey County (other municipalities) | additional residential unit (ARU) | Not published – check zoning by-law | Not published – check zoning by-law | None found | Guide |
| Bruce County | additional residential unit (ARU) – zoning set by local municipality | Not published – check zoning by-law | Not published – check zoning by-law | Affordable ARU Funding Program: up to $50,000 or 75% of construction cost, forgivable over 10 years, registered on title … | Guide |
| Haliburton County | accessory / additional dwelling unit (incl. tiny homes) | Not published – check zoning by-law | Not published – check zoning by-law | None found | Guide |
| Northern Ontario · 4 municipalities · Read the Northern Ontario page | |||||
| Greater Sudbury | additional dwelling unit (registered secondary unit) | Not published – check Zoning By-law 2010-100Z | accessory building 8 m | GSCIP Not-for-Profit ADU program only; none found for homeowners | Guide |
| North Bay | additional dwelling unit (ADU) | no maximum GFA for detached ADU (By-law 2025-37); up to size of main dwelling, subject to coverage and setbacks | Not published – check Zoning By-law 2015-30 | Growth CIP and District of Nipissing Housing Services ADU Program named; amounts not published | Guide |
| Thunder Bay | additional dwelling unit (Type C = separate accessory building) | Not published – check zoning by-law | Not published – check zoning by-law | Housing CIP (HAF): ADU grant 100% eligible costs up to $20,000/unit; permit fees grant up to $10,000; servicing grant up to $10,000 … | Guide |
| Sault Ste. Marie | additional dwelling unit (ADU) | no size limit stated; pre-approved designs 448, 680 and 732 sq ft | check max storeys in zoning by-law (updated Oct 2025) | Housing CIP Per Door Grant for 1-4 new units incl. garden suites with affordability agreement (amount not published) … | Guide |
Town names link to the official municipal source we used. “Not published” means we could not confirm the number from the town’s own pages or by-law text. Full detail for every row, including setbacks, parking, fees and servicing, is in the Rules Checker.
Last checked October 2026 · Sources: municipal zoning by-laws and ARU / ADU pages linked in each row
Found your town? Now check your lot.
A town rule is the ceiling. Your survey, septic, slope and services decide what actually fits. The $399 + HST Lot Report checks your address against all of it in 48 hours.
Go Deeper on Your Region
Each page has the full rules, local costs and traps, grants with deadlines and the official links.
Simcoe County local pages: Barrie · Orillia · Innisfil · Bradford West Gwillimbury · New Tecumseth · Springwater · Oro-Medonte · Severn and Ramara · Midland · Tiny Township · Wasaga Beach and Collingwood · Clearview · All of Simcoe County. We build in Simcoe County and Georgian Bay; if you are here, see our Simcoe garden suite builder page or ICFhome.ca.
On Septic? Different Game.
The three-unit guarantee and the December 2024 relief apply to urban land with full municipal services. On a rural lot with a well and septic, the township’s by-law is the whole story, and the septic bed is usually the first thing that says no.
Many townships now allow a permanent detached ARU on rural lots, often with a distance limit from the house (30 m in Tiny and Ramara’s hamlet zones, 50 m in Clearview, 75 m in Severn’s rural zones). Others still only allow a temporary garden suite: a temporary use by-law under the Planning Act for up to 20 years, with extensions, and an agreement to remove the unit later. That is a rezoning application, with fees and a public meeting, not just a building permit.
Rule of thumb from the field: get the septic checked before anything else. A designer can tell you in one visit whether the existing system can take the extra flow. Septic designs go through SepticReplacement.ca. The full rural process is on our temporary garden suite and rural and septic pages.
Reading a Rules Table Without Getting Burned
Read “the lesser of” twice
“Lesser of 50% of the house or 80 m²” on a small bungalow means the 50% wins. People design to the big number and get a correction notice back.
Check the zone, not just the town
Most towns have different numbers for urban, estate, rural and agricultural zones. Caledon, Brampton and Ottawa all split their rules by zone. Look up your zone on the town map first.
Do not trust a closed grant
Several 2025 programs in this table are already closed or fully subscribed. Never build a budget on a grant until you have an approval letter, and never start work before it.
Old by-law, new law
Some consolidated by-laws we read still show pre-Bill 23 wording. Where a by-law conflicts with the Planning Act or O. Reg. 299/19 on an urban serviced lot, the provincial rule wins. Ask the town how it is applying it.
Pre-consult before you pay for drawings
Most planning departments will look at a sketch and a survey before you commit. Twenty minutes on the phone is cheaper than paying a designer to draw the same building twice.
Skip the PDFs. Check Your Town in One Click.
The free Rules Checker shows every field we have for your municipality, the drawings you will need and the next step. No email, no account.
Rules by City Questions
Can I build a garden suite anywhere in Ontario?
On most urban lots with town water and sewer, yes. The Planning Act lets you have up to three units on a serviced urban residential lot, and one can be in a separate backyard building. On rural lots and lots on septic, the province does not guarantee it, so your township’s own by-law decides, and some still treat a backyard unit as a temporary garden suite.
Which Ontario city has the biggest garden suite size limit?
In our data, the largest published caps are on rural and farm lots: Centre Wellington allows a detached unit up to 186 m² on agricultural lots, Puslinch 130 m², Lakeshore 120 m² (140 m² agricultural). Toronto allows 120 m² for a two-storey suite. North Bay and Niagara Falls publish no size cap at all, only coverage and setbacks.
Which city has the smallest limit?
Brampton, at 35 m² (about 377 sq ft) in residential zones, is the tightest published cap in our table. Mississauga allows 55 m² one storey on lots of 550 m² or less. Ottawa caps a coach house footprint at 80 m² or 95 m² depending on the area, and lower on a small house or yard. Check the size limits page for every town side by side.
Did Ontario change the garden suite rules in 2024?
Yes. Amendments to O. Reg. 299/19 decided in December 2024 (ERO 019-9210) apply to urban residential land that allows three units. They guarantee at least 45% lot coverage, override floor space index limits, angular plane rules and ARU-specific minimum lot sizes, and cap the separation a town can require between residential buildings at 4 m. Towns still set size, height and setbacks.
Do I pay development charges on a garden suite?
Usually not for the second or third unit on a lot with a house. The Development Charges Act exempts additional units, including one in an ancillary building, on lots with a detached, semi or townhouse. Education charges and special cases vary, so confirm with your town before you budget. More on our development charges page.
What does garden suite mean in a township?
Often something different. In many rural townships a garden suite is a temporary, usually portable unit approved by a temporary use by-law under the Planning Act, for up to 20 years with extensions, tied to a removal agreement. Essa, Ramara, Severn, Tay, Tiny and Cavan Monaghan all use the term this way. See our temporary garden suite guide.
Are there grants for garden suites in 2026?
Some. In our data the open or listed programs include the County of Simcoe Secondary Suites Program (up to $50,000 forgivable), Bruce County (up to $50,000), Muskoka MAHIP ($40,000 or $50,000), Hamilton (up to $40,000), Kingston (up to $40,000) and Puslinch. Several 2025 programs are closed. Our funding directory keeps the status current.
How accurate is this table?
Every row was checked against the town’s own page or by-law in October 2026, and every town name links to that source. Where a number was not published or we could not confirm it, we say so instead of guessing. It is still a summary, not a zoning certificate: confirm with your town’s zoning review before you design.