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Secondary dwelling units in Ottawa
An SDU (secondary dwelling unit) is a complete second home tucked inside your house: its own front door, its own kitchen, its own bathroom.
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Secondary dwelling units
Legal is the whole point
An SDU (secondary dwelling unit) is a complete second home tucked inside your house: its own front door, its own kitchen, its own bathroom. Homeowners build them for rental income, for a parent who wants to live close by, or for grown children who are not ready for Ottawa rents. You will also hear them called additional dwelling units, in-law suites or basement apartments.
An SDU only does its job if it is legal. A unit built without permits can cause trouble with your insurance, can come back to bite you when you sell, and can put the people living in it at risk. The rules come from two places:
- The City of Ottawa decides whether your property can have a secondary unit. Its pages on adding an apartment or a coach house (it now calls them additional dwelling units) explain where they are allowed.
- The Ontario Building Code decides how the unit is built: fire separation between the two homes, safe ways out, smoke and carbon monoxide alarms, and ceiling heights.
A building permit is required to create one.
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Secondary dwelling units
What the work usually involves
- An entrance for the unit that meets the rules
- Fire-rated separation between the two homes, including the ceiling, doors and ductwork
- A kitchen and a bathroom, which means new plumbing and electrical
- Windows and exits that meet the Code for bedrooms and living space
- Heating and ventilation planned for two households instead of one
Is your house a good candidate?
Some houses convert easily. Others need more work, usually because of ceiling height, where the stairs are, or how the plumbing can drain. The fastest way to find out is to have us look. The consultation is free, and you will get a straight answer about your house before you spend a dollar on drawings.
Whole job or one part
The whole project, or any part of it
Carleton Prime can take on the whole project, turnkey, or just the part you need: one phase, or one trade such as the framing, drywall, tile, flooring or painting. Builders, general contractors, architects, designers and engineers can also bring us in as a subcontractor and an extra, experienced member of the team.
Frequently asked questions
Are secondary dwelling units allowed in Ottawa?
In a lot of Ottawa homes, yes. Where they are permitted is set by the City, and its pages on additional dwelling units lay out the details. The terms are explained on our additional dwelling units page.
Is a building permit required for a basement apartment?
Yes. A building permit is required to create a secondary dwelling unit, and the unit has to meet the Ontario Building Code.
Can an already-finished basement become an SDU?
Often, yes, though it usually means opening some walls and ceilings to add fire separation and bring the space up to Code. We will tell you what can stay and what has to change.
Is an SDU the same as an ADU?
They are two names for the same idea: a second self-contained home on the property. Additional dwelling unit is the City of Ottawa's current term. Our additional dwelling units page explains the terms and covers coach houses.
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The permit, Building Code and bylaw points on this page come from these authorities. Rules change, so check the current version before relying on any of it.
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