How Many Exits Does a Basement Apartment Need?

Egress fails more basement suites than any other requirement. It’s also the one where the answer most often gets simplified into something wrong — “you need two exits,” “you need a separate door,” “any window will do.”

The actual requirement is specific, it’s written down, and it’s checkable with a tape measure. This guide sets it out. Because provincial codes differ in places, jurisdictions are stated separately where they diverge.

What the code actually requires

The governing provision across Canadian provincial codes is Section 9.9.10, Egress from Bedrooms, in Part 9 of the building code as adopted in each province.

The core rule: except where the suite is sprinklered, each bedroom — or combination bedroom — must have at least one outside window or exterior door that opens from the inside without the use of keys, tools or special knowledge, and without the removal of sashes or hardware.

Note what that means structurally. The requirement attaches to each bedroom, not to the suite as a whole. A basement apartment with two bedrooms needs compliant egress from both, regardless of how good the main entrance is.

Where a bedroom is located in an unsprinklered suite in a basement, an escape window or door must be located in the bedroom itself — not down the hall, not in the living room.

The provincial codes:

• Ontario Building Code — the current edition is the 2024 Code
• BC Building Code
• National Building Code – Alberta Edition, applied under the Safety Codes Act

All three carry the same core dimensions. Where they differ is mainly sill height treatment in basements, covered below.

Egress windows in detail

The numbers, and what each one actually means.

Unobstructed opening area: not less than 0.35 m² (3.77 sq ft).

This is the clear opening — the hole a person can pass through when the window is fully open. Not the glass area. Not the frame. A large picture window that only tilts open at the top fails, however impressive it looks.

No dimension less than 380 mm (15 inches).

Both dimensions matter independently. A window can reach 0.35 m² total while having one side under 380 mm — a long narrow slot, for instance. That fails. Height, width and area must all clear.

It must maintain the required opening during an emergency without additional support.

The window has to stay open on its own. A hinged casement that swings shut, or a slider that won’t stay put, doesn’t satisfy this — someone escaping shouldn’t have to hold it.

It must open without keys, tools or special knowledge, and without removing sashes or hardware. A window painted shut, security-barred without a quick-release, or missing its crank handle is non-compliant regardless of its dimensions.

Sill height: generally a maximum of 1,000 mm above the floor, except for basement areas, which provinces treat differently — Ontario commonly applies a 1.5 m maximum in basements. Confirm which applies to you, because it’s one of the genuine cross-province differences.

Window wells: a clearance of not less than 760 mm must be provided in front of a window that opens into a well.

That last figure is the one almost nobody publishes, and it’s a common retrofit failure. Enlarging the window is pointless if the well in front of it is too shallow for a person to turn around and climb out. Size the well and the window together.

When a second exterior exit is required

Three situations change the picture.

The sprinkler exemption. The bedroom egress window requirement applies “except where the suite is sprinklered.” A sprinklered suite is treated differently. For most homeowners retrofitting a basement, sprinklering is more expensive than enlarging a window — but it’s genuinely an alternative route, and worth pricing if your windows are hard to enlarge (deep foundations, a driveway or neighbouring structure directly outside, heritage constraints).

Number of units and building configuration. As you move from a second unit toward a triplex or larger, code requirements for shared exit stairs and protected exiting step up. Calgary lists “protected exiting” among the safety elements its incentive programme reimburses, which is a useful signal of how routinely it comes up.

Where the suite’s only access is through the main dwelling. That isn’t a second unit at all under most definitions — independent access is one of the four elements that make a suite self-contained.

What is generally not required: a separate exterior door for a basement apartment, provided every bedroom has compliant egress and the unit has independent access. The “you need your own door” belief is the most common oversimplification here, and it leads people to budget for cutting a foundation entrance they may not need.

Shared vs separate entrances

This distinction saves real money and is widely misunderstood.

Independent access means the occupant can get in and out without passing through the main dwelling’s living space. It does not automatically mean a separate exterior door.

The City of Calgary is explicit: the entrance must be accessible from outside without passing through the main dwelling unit, and a shared stairwell is acceptable provided each unit has its own private entrance off it. A common indoor landing, with the main house’s door on one side and the suite’s on the other, satisfies the requirement.

That’s frequently a much cheaper solution than excavating and cutting a new below-grade entrance — which involves concrete work, a stairwell, drainage and often a retaining structure.

Where a shared stairwell is used, expect the fire separation requirements to apply to it — Alberta requires solid core doors at least 45 mm thick with self-closing devices between dwellings and in common spaces.

Common failures and what retrofits cost

The failures, in order of frequency:

1. Window too small. Existing basement windows in older houses are frequently well under 0.35 m².
2. One dimension under 380 mm. Common in older horizontal slider windows.
3. Window won’t stay open, or can’t be opened without tools.
4. Window well too shallow — under the 760 mm clearance.
5. Sill too high above the floor.
6. A bedroom with no exterior window at all — a converted interior room. This one can’t be fixed with a window; the room simply isn’t a legal bedroom.

What retrofits involve: enlarging a below-grade opening means cutting the concrete foundation, installing a new lintel, fitting the window, and excavating and building the window well with proper drainage. It’s a real job involving structural work, but a defined one — and considerably cheaper than the ceiling height fix, which requires underpinning.

We don’t publish a cost figure, because it varies with foundation type, depth, access and how many windows need doing. What we’d say is that it’s usually in a different, lower category than underpinning — so if egress is your only failure, the project is normally viable.

The order to check: ceiling height first (the expensive one), then egress, then separation and alarms. That sequence tells you within an hour which category your project is in.

Who signs off

The building permit authorises the work. Inspections confirm it was done as approved — and egress is checked at the framing stage, before anything is covered.

The practical rule: don’t drywall over a new egress opening before it’s been inspected. Reopening finished work is how a modest retrofit becomes an expensive one.

For a basement apartment, expect the inspector to verify the clear opening dimensions, that the window operates without tools and stays open, the window well clearance, and the sill height — plus fire separation and interconnected alarms as separate items.

Where the work involves structural changes to the foundation, a designer or engineer may need to be involved before the permit is issued. Our planning and permits page covers the approvals stage.

Code provisions are amended periodically and provinces adopt them with variations. Confirm the current requirements for your jurisdiction with your municipality or a qualified designer before relying on any dimension for a design.

Find out whether your basement can meet egress

Egress is measurable today, and if it’s your only failure the project is usually viable. What matters is checking it alongside ceiling height, since the two together determine the scale of the work.

HouseLyft’s free property assessment establishes what your property supports and what compliance would require. Our secondary suites overview covers the category, and our FAQ answers common questions. Request your free report.