Garden Suites in Peterborough and the Kawarthas: city plans, township by-laws
The City of Peterborough has pre-approved detached ARU plans, a fee rebate and an interest-free loan. Cavan Monaghan still does garden suites the old way, by temporary use by-law. Selwyn and Kawartha Lakes sit in between. Same county name on the map, completely different permit paths.
At a glance
Each municipality sets its own zoning. The numbers here come from their own published guides, linked below.
In the City of Peterborough you can build one detached ARU, smaller than the house, up to 4.3 m high and two bedrooms, with pre-approved plans available and up to $5,000 in permit fees rebated. In Cavan Monaghan a garden suite is a temporary unit of 50 to 100 m² approved for up to 20 years. Selwyn and Kawartha Lakes allow detached units with septic and distance limits.
Four Municipalities, Four Rulebooks
The City of Peterborough is a separate city with full municipal services and its own zoning. Cavan Monaghan and Selwyn are townships in Peterborough County, mostly on wells and septic outside a few serviced settlements such as Lakefield. The City of Kawartha Lakes is one big single-tier municipality stretching from Lindsay to Bobcaygeon, Fenelon Falls and the lakes, with a lot of private services.
So the first question is not “how big can it be”. It is “which municipality am I in, and am I on sewer or septic”. A lot with a Peterborough mailing address can easily be in Selwyn or Cavan Monaghan. Check your tax bill.
| Municipality | What they call it | Detached unit size | Height / distance | Approval path |
|---|---|---|---|---|
| City of Peterborough | Additional residential unit (ARU) | Smaller than the main unit; max 2 bedrooms | 4.3 m max; 1.2 m from back of house; 0.6 m from side/rear lot lines | Building permit; pre-approved plans available |
| Cavan Monaghan | Garden suite | Min 50 m²; max 100 m² or 40% of the house floor area | 5.0 m, one storey; 3.0 m from the house | Temporary use by-law (up to 20 years) plus agreement, then permit |
| Selwyn | Second unit | 60% of house footprint (A, RU zones); 40% (RR, R1, R2) | Not above the house; one storey in R1/R2; 8 m or 2 storeys over a garage in A, RU, RR; within 30 m | Registration, then building permit |
| City of Kawartha Lakes | Additional residential unit (ARU) | Equal to or less than the main unit | Up to 10 m and 1.2 m from side/rear lines when the ARU is on an upper storey | Registration under By-law 2020-162, usually a building permit |
Last checked October 2026 · Sources: City of Peterborough, Cavan Monaghan Garden Suite Information, Selwyn Secondary Units Guideline (July 2025), Kawartha Lakes ARU Guide
Peterborough’s Detached ARU Rules in Full
Peterborough allows one ARU in an accessory building on a lot with a single detached, semi-detached or row house. It has to be smaller than the main unit and can have no more than two bedrooms. The city does not give an absolute square-metre cap. The real limit is lot coverage: all accessory buildings together cannot cover more than 10% of the lot. On a 40 x 100 ft lot, that is 400 sq ft, minus your shed.
That 10% rule and the 4.3 m height cap are the two that shape most Peterborough suites. 4.3 m is a one-storey building with a modest roof. A loft or a unit over a garage is not going to fit without a variance. Our minor variance guide covers when that is worth trying.
| Rule | City of Peterborough |
|---|---|
| Setback from back of house | 1.2 m minimum |
| Setback from side or rear lot line | 0.6 m minimum |
| Accessory lot coverage | 10% max, all accessory buildings combined |
| Parking for the ARU | Area 1: 0 spaces; Area 2: 1; Area 3: 1 (tandem allowed). Find your area on the city map |
| Fire access | Hydrant to pumper plus firefighter path to the ARU door: 90 m max. Pumper to ARU door: 45 m max |
| Access route | 0.9 m minimum width, hard stable surface, cross-slope 2–5%, avoid stairs |
| Servicing | Must connect to public water and wastewater, unless the zone does not require municipal services for the house |
| Floodway | Not permitted |
Last checked October 2026 · Source: City of Peterborough: Building a New ARU
The 45 m fire rule kills more backyard suites than zoning. Measure from where a pumper truck can park on the street to the suite’s door, along a path a firefighter can walk. On deep lots and lots with the garage across the side yard, you can be over 45 m before you notice. If you are, you need an alternative solution acceptable to Peterborough Fire Services, which usually means sprinklers or upgraded fire separation.
Pre-Approved Plans and an Interest-Free Loan
The Pre-Approved Plans Program
Peterborough offers pre-approved plans for detached ARUs, designed by local BCIN or P.Eng. designers and already checked for Building Code compliance. Applications that use a plan with no changes get priority review. The catalogue currently lists one design, the Dalton 1, and the city says more are coming. The page does not say what the plans cost; the designer’s contact information is included, so ask them.
Here is what the pre-approved plan does not do for you. The city still wants your own site plan, a site servicing report and construction drawings. Your zoning still has to permit the unit, and heritage or conservation authority approval may still apply. Change anything about the plan and it goes back to normal review. Our pre-approved plans round-up compares Peterborough’s program with the others in Ontario.
Missing Middle CIP money
The city’s Missing Middle Community Improvement Plan is listed as in effect (updated January 2026) and covers second, third and fourth units on a lot:
- Development charge rebate for up to three additional units, capped per unit at the city-wide apartment rate.
- Building permit fee rebate of 100% of City building permit fees, up to $5,000 per owner, paid after occupancy.
- Municipal loan of up to $10,000 per unit, max $30,000 per owner, interest-free for three years.
Eligibility depends on the unit being an “eligible missing middle building typology”, and the full criteria are in the MMCIP document. Ask planning at 705-742-7777 ext. 1501 before you count on it. Details are on the city’s Grants and Incentives page.
Using a pre-approved plan? You still need the rest.
Our Urban Pre-Approved Wrapper adds the site plan, grading coordination, forms and heat loss a city plan leaves out. From $1,499.99 + HST.
Cavan Monaghan: The Temporary Garden Suite, by the Book
Cavan Monaghan’s zoning by-law defines a garden suite as a one-unit detached dwelling with a kitchen and bathroom, ancillary to an existing house and “designed to be portable”. It is approved by a Temporary Use By-law for up to 20 years, with extensions of up to 3 years, and you sign an agreement with the Township covering maintenance, changes and eventual removal.
The size and placement rules
- Minimum 50 m², maximum 100 m² or 40% of the house floor area
- Maximum 5.0 m high and one storey
- At least 3.0 m from the house and from buildings on the next lot
- Not closer to the road than the front wall of the house
- One garden suite per lot, one shared driveway, at least one parking space
The process, in order
- Confirm your zone permits it
- Apply for the Temporary Use By-law and pay the fee
- Sign the maintenance and removal agreement
- Get a building permit (OBC 9.38) and an electrical permit
- Submit drawings, a site plan with parking and drainage, and the septic approval
Septic is the part people underestimate. Where there is no municipal sewer, the Township wants a permit or letter of compliance from Peterborough Public Health confirming your existing system can take the suite, or a permit for a new system. Services should extend from the existing house where there is no municipal water or sewer.
Note the 40% rule: on a 1,500 sq ft bungalow, 40% is about 600 sq ft, not the 1,076 sq ft (100 m²) maximum. The smaller number wins. And because the suite must be designed to be portable, a full basement is off the table. A pier, helical pile or skid foundation is the honest answer here. Our temporary garden suite guide explains the agreement and removal side.
Selwyn and Kawartha Lakes: Permanent, With Strings
Selwyn Township
Selwyn’s July 2025 guideline allows detached second units in the Agricultural, Rural, Rural Residential, R1 and R2 zones. They are not allowed in an accessory building in the Lakeshore Residential zone, in an EP zone or floodplain, on a lot that already has a garden suite or sleeping cabin, or on a property that fronts a private road. That last one rules out a lot of cottage lots on the lakes.
The detached unit must be within 30 m of the house, in the rear or interior side yard, no taller than the house, and cannot be a mobile home or have a basement. It needs its own entrance, at least 7.5 m² of private outdoor space, and one parking space on top of the house’s (each space 3 m by 6 m). Garden suites are still possible through a temporary use zoning by-law in zones that allow single detached or semi-detached houses.
You register the unit before you apply for the building permit. On private services, Selwyn says you may need to upgrade the septic system or install a separate one, and show there is enough potable water. Selwyn’s own building department issues septic permits.
City of Kawartha Lakes
Kawartha Lakes allows one ARU in an accessory building plus one in the house. The ARU’s floor area must be equal to or less than the main unit. On private services, the lot must be at least 0.4 hectares (about an acre) with adequate sewage and water. The ARU cannot be in a floodplain, water setback or hazard land, in the EP, HL or OS zones, or in the Oak Ridges Moraine area, and must meet MDS from livestock barns.
Every ARU must be registered under By-law 2020-162, and an unregistered unit is considered illegal. Permits are generally issued within 10 business days of a complete application. For the septic side, the city’s guide points you to the Building Division’s Sewage System Area Inspector.
Where people get it wrong in the Kawarthas: assuming waterfront means more room. It usually means less. Water setbacks, floodplain mapping, Lakeshore Residential zoning and private roads each knock out a detached unit on their own. Check all four before you fall in love with a site by the dock.
Lake Country Septic: Know Your Litres
Selwyn’s sewage system guide lays out the Building Code math plainly. Daily design flow starts at 750 litres for a one-bedroom dwelling, 1,100 for two, 1,600 for three and 2,000 for four. Add bedrooms or fixtures and the flow goes up. Any time you add bedrooms, add fixtures or exceed the existing system’s capacity, a new sewage application is required before you build.
Put a two-bedroom garden suite next to a three-bedroom house and the designer is looking at roughly 2,700 litres a day on one system. A 1980s cottage system built for weekend use will not have that. Shallow soils, Shield rock north of the Kawarthas and the lake setbacks all push toward raised beds, tertiary treatment units or a separate small system for the suite.
- Pull the old septic permit. Peterborough Public Health, the township or the city may have it on file.
- Check the water too. Kawartha Lakes and Selwyn both want proof of adequate water for the extra unit.
- Get capacity confirmed before you design the suite. The bed location often decides where the suite can go.
- Price the septic first. On some lots it is the biggest single line after the building itself.
We do not design septic systems. Septic design for permits is done through SepticReplacement.ca. Our rural and septic guide walks through the capacity check.
We Build in Simcoe Only. Here’s What We Do for Peterborough.
Plain and simple: ICFhome.ca builds in Simcoe County and the Georgian Bay area. We do not build in Peterborough, the Kawarthas or Cavan Monaghan. For construction, hire a local builder with a current HCRA licence and check them on the Ontario Builder Directory.
What we can do for any lot in the region: read your zoning, check the septic and fire-access questions before you spend on drawings, prepare a permit package, or review the quote your local builder gave you.
$399 + HST Feasibility Report
Zoning, 45 m fire path, septic and servicing for your exact lot, in 48 hours.
Rural Garden Suite Pack
Drawings, site plan, heat loss and septic design through our partner. From $2,499.99 + HST.
Talk to a Builder
30 minutes for $149.99 + HST, or a 60-minute quote review for $249.99 + HST.
Find out which rulebook your lot falls under
City ARU, township second unit or 20-year garden suite: the path decides the foundation, the septic and the budget. We sort it out for your property in 48 hours.
Peterborough and Kawarthas Questions
Can I build a garden suite in Peterborough?
Yes. The City of Peterborough allows one additional residential unit in an accessory building on lots with a single detached, semi-detached or row house. It must be smaller than the main unit, have no more than two bedrooms, be no taller than 4.3 m, and all accessory buildings together cannot cover more than 10% of the lot.
Does Peterborough have pre-approved garden suite plans?
Yes. The city’s Pre-Approved Plans Program offers detached ARU designs by local BCIN or P.Eng. designers, already checked for Building Code compliance, with priority review if you make no changes. The catalogue lists the Dalton 1 so far. You still need your own site plan, site servicing report and construction drawings.
Are there grants for an additional unit in Peterborough?
The Missing Middle Community Improvement Plan offers a development charge rebate for up to three additional units, a 100% building permit fee rebate up to $5,000, and an interest-free three-year loan of up to $10,000 per unit, to a $30,000 maximum. Eligibility depends on the building type, so confirm with City planning first.
How long can a garden suite stay in Cavan Monaghan?
Up to 20 years under a Temporary Use By-law, with extensions of up to 3 years at a time. The owner signs an agreement with the Township covering maintenance, alterations and eventual removal. The suite must be 50 to 100 m² or 40% of the house floor area, one storey and no more than 5.0 m high.
Who approves the septic for a garden suite in Cavan Monaghan?
Peterborough Public Health. The Township requires a permit or letter of compliance from Peterborough Public Health confirming your existing septic system is adequate for the garden suite, or a permit for a new system, as part of the building permit application.
How far from my house can a second unit be in Selwyn?
No more than 30 m from the principal structure, in the rear or interior side yard. It cannot be taller than the house, cannot be a mobile home or have a basement, and is not allowed in an accessory building in the Lakeshore Residential zone or on a lot that fronts a private road.
Can I build an ARU on a septic lot in Kawartha Lakes?
Yes, if the lot is at least 0.4 hectares and has adequate sewage and water. The existing septic system often needs review and may need an upgrade. The ARU cannot be in a floodplain, water setback or hazard land, and must be registered under By-law 2020-162.
Will ICFhome.ca build my garden suite in Peterborough?
No. We build in Simcoe County and the Georgian Bay area only. For Peterborough and the Kawarthas we offer the free Rules Checker, the $399 + HST Feasibility Report, permit packages and paid builder calls, and you hire a local HCRA-licensed builder for construction.