Legal secondary units in Kingston, built start to finish
We design, permit and build secondary units in Kingston, Ontario, also called additional residential units (ARUs). Garden suites, basement apartments and garage conversions, handled by one team from the first zoning check to the occupancy permit.
- Design, permits and build in one contract
- Help applying for City incentives
- Local office on Princess Street
Secondary unit types we build
Kingston's zoning allows an additional unit inside the house, attached to it, or in its own building in the yard, as set out in the City of Kingston ARU rules. The right choice depends on your lot, your budget and who will live there.
Garden suites and detached ARUs
A separate small home in your back yard. The most privacy for a tenant or a parent, and the largest City incentive.
Garden suite buildsBasement apartments
Turn an unfinished or underused basement into a legal one or two bedroom suite with its own entrance.
Basement apartment conversionsGarage conversions
Reuse a detached or attached garage as a self-contained unit, often with less site work than building new.
Garage to suite conversions| Type | Where it goes | Best for | Max City incentive* |
|---|---|---|---|
| Garden suite (detached) | New building in the yard | Privacy, long-term rental, aging parents | Up to $40,000 |
| Garage conversion (detached) | Existing detached garage | Lots with a sound garage and services nearby | Up to $40,000 |
| Basement apartment (interior) | Inside the main house | Lower budgets, fastest rental income | Up to $30,000 |
| Attached addition | Built onto the house | Lots too small for a detached unit | Up to $30,000 |
*Forgivable loan, capped at 50% of project cost, with five years of affordable rent. See the Kingston ARU incentive program guide for the conditions and current waitlist status.
How a secondary unit project works with us
Most delays on ARU projects come from zoning surprises, incomplete permit drawings and trades that are booked separately. We run the whole sequence so those gaps do not open up.
- Free property checkWe review your lot against Kingston's ARU zoning rules, servicing maps and constraint areas before you spend anything.
- Design and budgetYou get a layout, a written itemized quote and a clear picture of which incentives you may qualify for.
- Permits and incentive paperworkWe prepare permit drawings, apply for the building permit and help with the City incentive application.
- ConstructionOne project manager schedules every trade and coordinates each City inspection.
- Final inspection and occupancyWe close out the permit so the unit is legal, insurable and ready to rent.
- Move-inYour tenant or family member moves in. We hand over warranties, manuals and as-built details.
What does your town allow?
Every municipality writes its own ARU rules. Pick a town to see the headline numbers, then open the full guide with official sources.
Kingston: City of Kingston
- Units per lot
- Up to 4 (low-rise residential)
- Size limit
- Up to the main house GFA
- Development charges
- Exempt
- Best incentive
- Up to $40,000 forgivable loan (waitlisted)
Kingston allows up to four units per lot in low-rise residential areas, including attached, detached, garage and basement ARUs. An ARU can be as large as the main house and needs one parking space. The City offers forgivable loans of up to $40,000, now waitlisted.
Kingston ARU guideFree tools to plan your unit
Built on the same official data as our city guides.
Why build a secondary unit in Kingston now?
Kingston has a steady rental market driven by Queen's University, St. Lawrence College, CFB Kingston and the hospitals. Ontario law now allows up to three homes on most serviced residential lots (the main house plus two units), and the City offers forgivable loans that can cover a large share of construction for owners who rent affordably.
Homeowners usually build for one of three reasons:
- Rental income that helps carry the mortgage.
- Family housing for a parent who wants independence close by, or an adult child saving for a home.
- Long-term property value from a second legal dwelling on the same lot.
Whichever it is, the unit has to be legal to be worth anything. An unpermitted suite can void your insurance and is hard to sell. Our design and permit service exists to get that part right first.
Financing a secondary unit
Beyond the City incentives, CMHC-insured refinancing and home equity lines are the most common ways owners pay for an ARU. The federal Secondary Suite Loan Program announced in 2024 was cancelled before it launched. Our secondary suite financing guide explains what is actually available in 2026.
Secondary unit questions we hear most
What is an additional residential unit (ARU) in Kingston?
An ARU is a second self-contained home on a residential lot, with its own kitchen, bathroom and entrance. In Kingston it can be inside the house (such as a basement apartment), attached to it, or detached (such as a garden suite or converted garage).
Do I need a building permit for a secondary unit?
Yes. Every new ARU in Kingston needs a building permit and must meet the zoning bylaw and the Ontario Building Code. Existing unpermitted units also need a permit and an inspection to be made legal. We prepare the drawings and handle the application for you.
Can I get money from the City to build an ARU?
Possibly. Kingston offers forgivable loans of up to $40,000 for a detached ARU and up to $30,000 for an interior ARU, in exchange for renting at an affordable rate for five years. As of October 2026 new applications go on a waitlist and need a permit issued by December 1, 2026.
How much does it cost to build a secondary unit?
It depends mostly on the type of unit, its size, and how much servicing work your lot needs. A basement conversion usually costs less than a new detached garden suite. We give you a written, itemized quote after a free property check, so you know the number before you commit.
Which areas do you serve?
We are based in Kingston and build across Eastern Ontario, including Napanee, Picton and Prince Edward County, Belleville, Brockville and Cobourg. Each municipality has its own ARU rules, so we publish a free guide for each one.
More answers on our secondary unit FAQ page.
Find out what your property can hold
Send us your address and what you have in mind. We will check the zoning, flag any servicing issues and tell you which incentives you may qualify for, at no cost.