In short
- The City of Ottawa allows up to two additional dwelling units on a lot with a house, and a lot on municipal water and sewer may have both inside the building.
- A lot on a well or septic is limited to one additional dwelling or coach house.
- HomeStars prices a legal secondary suite in Ottawa at $80,000–$120,000; a basement kitchen or kitchenette alone is $20,000–$50,000.
- Ontario's second-unit page lists a 30-minute fire separation between units, reducible to 15 minutes with interconnected smoke alarms in the whole house, and a 1.95 m basement ceiling.
- A building permit is needed even where little or no work is planned, because a change of use is reviewed.
Typical prices in Ottawa
| Job | Typical range | Notes |
|---|---|---|
| Legal secondary suite, one-bedroom, all-in | $80,000–$120,000 | HomeStars Ottawa, 2026; older homes needing structural or asbestos work can pass it |
| Basement kitchen or kitchenette | $20,000–$50,000 | From sink and mini-fridge to a full kitchen with gas line and cabinets |
| Egress window, per window | $3,500–$6,000 | Needed for every bedroom |
| Electrical upgrades, panel and circuits | $1,500–$5,000 | A separate electrical permit and an ESA inspection apply |
Sources. Seen 29.10.2026: City of Ottawa, Adding an apartment (additional dwelling units). Ontario, Add a second unit to your house, a page that warns some parts predate the 2022 land-use changes. HomeStars, 2026 Basement Renovation Cost Guide for Ottawa (updated 21/08/2026); the guide’s permit-fee and zoning statements were left out. City of Ottawa, Comprehensive Building Code Fee Schedule. City of Ottawa Building Code Services, egress windows advisory (August 2025).
What the City calls it
Ottawa uses the term additional dwelling unit for an apartment in the same building as a house, whether detached, semi-detached, linked-detached, duplex or townhouse. The City says these units are permitted in urban, suburban and rural areas where the property is fully serviced, under section 3.2 of the Official Plan and section 133 of the Zoning By-law. A lot may have up to two additional units, and three units in total.
Before 2005, secondary units were allowed only in some former municipalities: Cumberland-Urban, Gloucester, Nepean-Urban, Osgoode, Goulbourn and West Carleton. A unit that dates from that time still has to meet the Building Code and the Fire Code.
A permit even for a small change
The City says a building permit is required before adding a unit to an existing dwelling. Alterations to walls, a larger window, a new exterior door or an internal shared entrance all count. The City adds that even when little or no work is planned, the change of use is reviewed against the Ontario Building Code and other law.
The City’s development information officers answer inquiries within 2 to 3 business days.
The building rules in plain numbers
The Ontario page on second units lists the points a basement apartment meets. It warns that some of its content predates recent land-use changes, so the company confirms each figure with the City.
- Ceiling height: 1.95 m (6 ft 4¾ in) across the required floor area in a basement unit.
- Fire separation: 30 minutes between units. It can drop to 15 minutes if the whole house has interconnected smoke alarms.
- Smoke alarms on every level, outside sleeping areas and in each bedroom of the unit; carbon-monoxide alarms where the house has fuel-burning equipment or an attached garage.
- A separate electrical permit, inspected by the Electrical Safety Authority, and a light switch at the top and bottom of the stairs.
- Hot and cold water, a bathroom, a kitchen sink, access to laundry and a separate water shut-off for each unit.
- Bedroom windows that meet the City’s egress rule, described on the egress bedroom page.
Price: what the number covers
HomeStars’ Ottawa guide puts a one-bedroom legal suite at $80,000 to $120,000 all-in. That includes a kitchen ($20,000 to $50,000 on its own), a bathroom (see the basement bathroom page), egress windows at $3,500 to $6,000 each, and electrical upgrades of $1,500 to $5,000. The guide warns that older Ottawa homes needing structural or asbestos work can pass the range.
At $12.75 for each $1,000 of assessed value, minimum $117, the City’s fee on a $100,000 project comes to $1,275. Drawings come on top of that.
Rent
HomeStars lists one-bedroom rents of $1,200 to $1,800 a month in Centretown and Sandy Hill. Your address will differ, so work out payback from your own quote.
Where the rest of the cost sits
Whole-basement budgets, contingencies and permit timing are in the basement renovation cost guide. Water and insulation, which come before any drywall, are covered in moisture and insulation. The permit guide lists the other City rules.
Who prices the suite
A suite request goes from the Desk to one independent renovation company. It visits, measures, prices the suite line by line and applies for the permits in its own name.
Questions to ask the company
- Does the plan keep the suite inside the house, and how is the fire separation between the two units built?
- Who is the designer of record: the homeowner, or a person registered with a Building Code Identification Number?
- Does the price include a separate electrical permit, the ESA inspection and the heating and ventilation changes?
- How does a person leave the suite if the stairs to the main floor are blocked?
Have this ready for the call
- House type: detached, semi-detached or townhouse
- Whether the lot has City water and sewer, or a well and septic
- Floor plan or rough sketch with the stairs, the furnace and the water heater marked
- Ceiling height at the lowest beam and duct
- Current entrances, including any walk-out or side door
Questions people ask
How many apartments can an Ottawa lot have?
The City says a lot with a principal dwelling may have up to two additional dwelling units: two apartments in the same building, or one apartment and one coach house. The total, including the main unit, cannot pass three. A lot on well or septic is limited to one additional unit, and the Ottawa Septic Office confirms the system can take the load.
Does the suite need its own entrance?
The City’s page says the unit must have separate access on the ground floor of the principal dwelling, unless the building or fire codes allow another means. The City requires no extra parking space. If one is added, it cannot be in the front yard, and tandem parking in the existing driveway is allowed.
Do I need an architect or designer?
Where two additional units go inside the house, the Building Code asks for a person registered under a Building Code Identification Number to take design responsibility. A homeowner can take it for one additional unit when no other exists, the City notes. Ask the company which route your plan follows.
How does a suite affect taxes and insurance?
The City warns that the Municipal Property Assessment Corporation may change your property tax assessment, and rent counts as income under the Income Tax Act. Notify your insurer or broker early, since liability and the value of the home change after the unit is built.
Is there federal money for a suite?
The City mentions financial assistance from the Canada Mortgage and Housing Corporation’s Homeowner Residential Rehabilitation Assistance Program for certain additional dwelling units. Eligibility and amounts sit with CMHC.