Building a Secondary Dwelling Unit (SDU) in Ottawa

What is a secondary dwelling unit (SDU)?

Most second units are built in the basement, but they can be built in any part of the house, building code rules can vary depending on where the second unit is located in your house.

A SDU is a single, self-contained, rental apartment with its own kitchen and bathroom. While many are basement apartments. SDUs are also commonly referred to as "in-law suites".


Requirements to meet city code for an SDU

1. Does the ceiling height meet code, especially within the path of egress

2. Natural light calculation, based on the square footage of the living space

3. Fire & soundproofing the SDU from the main unit

4. Adding egress windows


A basement second unit is permitted to have a finished ceiling height of 1.95 m
(6’ 4¾”) over the entire required floor area, including,duct work, and the route inside the unit leading to the exit.



A fire separation can be a floor, wall, door with a self-closing device, or a combination of those things. It can be built using typical building materials such as lumber and drywall.


Lighting requirements for living and dining rooms are greater, so one must consider positioning of these spaces where you can provide adequate natural lighting through existing, enlarged, or new windows.


egress windows

Egress (emergency escape) You need at least 1 egress window in your basement suite, preferably in the opposite end of where the entrance is for maximum safety.

Fire Safety Items in SDU

  1. Egress Door and Window (for escape)
  2. Fire Rated Floor/Ceiling Assembly
  3. Smoke Alarms
  4. Sprinkler Systems (needed in some cases)
  5. Fire Rated Doors with Self Closing Mechanisms

These items are straight forward, and these are things that the city  looks for. All of the points listed deal with containment of a fire, and preventing the spread of fire from one unit to another, this to allow enough time for any occupants to evacuate.

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