What makes a basement apartment legal?
A legal basement apartment has a building permit, passes City inspections and meets the Ontario Building Code for secondary suites. That covers the smoke-tight separation between units (Type X drywall and sealed openings under the 2024 code), interconnected smoke alarms, carbon monoxide alarms, safe exits, ceiling height, light, ventilation and electrical work.
Legal status matters. It protects your tenant, keeps your home insurance valid, and adds a recognized second dwelling when you sell. It is also a condition of the City's interior ARU incentive.
Code items that decide the budget
These are the items that most often move the cost of a basement conversion up or down. The full rules are summarized in the HCRA guide to the 2024 Ontario Building Code.
| Item | Usually simple when | Gets more involved when |
|---|---|---|
| Ceiling height | Clear height already meets code | Ducts, beams or floor need lowering |
| Exits and windows | A walkout or large windows exist | New egress windows or a new door must be cut |
| Separation between units | Open ceiling, easy to drywall | Finished ceilings must be opened |
| Plumbing | Drains are near the planned kitchen and bath | Fixtures sit below the sewer line and need a pump |
| Heating and ventilation | System has capacity for a second zone | A separate system is needed |
| Moisture | Dry basement | Waterproofing or drainage work first |
Our basement apartment process
- Property check: zoning, height, exits, moisture and services.
- Layout and quote: a floor plan and an itemized written price.
- Permit: drawings and application to the City of Kingston.
- Build: framing, unit separation, plumbing, electrical, HVAC and finishes.
- Inspections and occupancy: we coordinate each inspection and close the permit.
Legalizing an existing basement suite
If your basement apartment was built without a permit, Kingston requires it to be legalized. An inspector reviews the unit and lists the deficiencies, then the work is completed under a permit. We can take that list, price it and do the work, so you end up with a legal unit and the paperwork to prove it.
Incentives for interior ARUs
Kingston's Interior ARU Incentive is a forgivable loan of up to 50% of project cost or $30,000, whichever is less. An Accessibility Grant adds $5,000 for units that meet accessibility criteria. Read the conditions in our Kingston ARU incentive guide, or compare with a detached garden suite.
Frequently asked questions
Is my basement tall enough for a legal apartment?
The Ontario Building Code sets a minimum ceiling height for secondary suites, with some allowance under beams and ducts. Many older Kingston basements meet it, some need ducts rerouted, and a few need the floor lowered. We measure during the property check so you know early.
Can I make my existing basement apartment legal?
Usually, yes. Kingston requires existing units to be legalized through a building permit. A building inspector visits, lists the deficiencies, and the work is completed to code. Common items are separation between units, smoke and carbon monoxide alarms, exits and electrical.
Does a basement apartment need a separate entrance?
It needs access that meets the Building Code for a safe way in and out. That can be a separate exterior door or, in some layouts, a shared entrance with a protected path. We design the option that suits your house and budget.
How much rent can a Kingston basement apartment earn?
It depends on size, location and finish. If you use the City interior ARU incentive, rent is capped for five years at 90% of average market rent, which in 2026 is $1,353 a month for a one bedroom and $1,588 for a two bedroom, utilities included.