In Alberta, the walls and floors between a secondary suite and the main house don't need a fire-resistance rating if they're covered by a continuous smoke-tight barrier of gypsum board at least 12.7 mm (0.5 in) thick, on both sides of the walls and on the underside of the floor framing (NBC(AE) 2023, 9.10.9.16). Doors in that barrier must be solid-core wood at least 45 mm (1.8 in) thick with a self-closing device (NBC(AE) 2023, 9.10.9.3). Both rules are in the second printing of the National Building Code, 2023 Alberta Edition, in force since 17 August 2026 (Government of Alberta, 2026).
Key takeaways
- As of October 2026, a house with a secondary suite can replace the usual 45 min fire separation between units with a continuous smoke-tight barrier of 12.7 mm (0.5 in) gypsum board (NBC(AE) 2023, 9.10.9.16).
- Every door in that barrier must be a solid-core wood door at least 45 mm (1.8 in) thick with a self-closing device (NBC(AE) 2023, 9.10.9.3).
- A furnace or water heater serving both units can sit in a service room lined with 12.7 mm (0.5 in) gypsum on both sides of its walls and under its ceiling framing (NBC(AE) 2023, 9.10.10.4).
- A suite's exterior exit door within 3 m (9 ft 10 in) of the other unit's window, at a corner of less than 135°, needs that window in wired glass or glass block (NBC(AE) 2023, 9.9.4.6).
- Sound between the units needs 150 mm (5.9 in) of insulation in the joists with resilient channel and 12.7 mm gypsum, or an STC rating of 43, or an ASTC rating of 40 (NBC(AE) 2023, 9.11.1.1).
- The City of Calgary's suite page lists the same 12.7 mm drywall and 45 mm doors, and adds an engineered foundation for any new exterior exit stairwell (The City of Calgary, 2026).
What fire separation does a secondary suite need in Alberta?
A smoke-tight barrier, not a rated wall. The general rule for homes is a fire separation of at least 45 min between suites, rising to 1 h where a dwelling unit has 2 or more storeys, basements included. Sentence (4) of the same Article then exempts a house with a secondary suite, as long as the walls and floor framing between the units carry continuous 12.7 mm (0.5 in) gypsum board (NBC(AE) 2023, 9.10.9.16).
The definition is narrow: a self-contained unit in a building with only one other dwelling unit, both forming "a single real estate entity" (NBC(AE) 2023, Division A, 1.4.1.2). A house split into two titles doesn't qualify.
The barrier has to be continuous: it stops smoke across its whole surface, and its gypsum joints must follow CSA A82.31-M (NBC(AE) 2023, 9.10.9.2). The City of Calgary asks for joints "taped and filled with drywall compound" (The City of Calgary, 2026).
Here's where the 12.7 mm (0.5 in) gypsum goes, as of October 2026:
| Element | Where the gypsum goes | Clause |
|---|---|---|
| Walls between the two units, or between a unit and a common space | Both sides of the wall | 9.10.9.16.(4) |
| Floor between the units | Underside of the floor framing | 9.10.9.16.(4) |
| Shared exit, such as a common stair | Both sides of its walls and the underside of the floor over it | 9.9.4.2.(2) |
| Service room with a furnace or water heater serving both units | Both sides of its walls and the underside of the floor over it | 9.10.10.4.(2) |
| Light-frame walls, columns and beams holding up the floor between units | Not less than 12.7 mm on the member | 9.10.8.3.(2) |
| Exterior wall within 1.2 m of an inside corner where the two units' openings meet | Interior face of the wall | 9.10.12.3.(3) |
Note: code minimums for a house with a secondary suite, not a fire rating for the assembly. The City of Calgary reviews them at permit and checks them at inspection.
Floors inside a house with a secondary suite don't have to be fire separations (NBC(AE) 2023, 9.10.9.4), and the floor rating table doesn't apply once the 12.7 mm barrier covers the framing (NBC(AE) 2023, 9.10.8.10). The Sentence names loadbearing steel too, so a steel beam and posts carrying the floor between the units get boxed in too. The Note says the light-frame rule doesn't cover heavy timber, masonry or concrete (NBC(AE) 2023, Note A-9.10.8.3.(2)), which is guidance, not a requirement.
What door goes between a suite and the main house?
A solid-core wood door at least 45 mm (1.8 in) thick, fitted with a self-closing device (NBC(AE) 2023, 9.10.9.3). That covers every door in the barrier: the suite's door onto a shared stair or hall, the main house's door onto the same space, and the service room door.
The code's Note, which is guidance rather than a requirement, treats these doors as giving a 20 min fire-protection rating without a CAN/ULC-S113 label (NBC(AE) 2023, Note A-9.10.9.3.(2)). You don't need to hunt for a labelled fire door.
Inside the suite, doorways can be sized for doors 1 890 mm (6 ft 2 in) high where the ceiling follows the suite's 1.95 m rule (NBC(AE) 2023, 9.5.5.1). The ceiling heights themselves are on the basement ceiling height guide.
Can a suite share a stair with the main house?
Yes, if the stair is lined as an exit. In a house with a secondary suite, an exit gets 12.7 mm (0.5 in) gypsum on both sides of the walls that separate it from the rest of the house and under the floor framing above it (NBC(AE) 2023, 9.9.4.2). Each door onto it then follows the 45 mm rule above.
The City of Calgary adds a layout rule for existing suites: the path to an exit can't run through the mechanical room (The City of Calgary, 2026). Plan the furnace room off the stair, not across it.
An upper unit reached by an outside walkway can need a second way out: where its door opens onto an exterior passageway with a floor rated under 45 min, one exit stair, and a height over 1.5 m (4 ft 11 in) above the ground (NBC(AE) 2023, 9.9.9.3).
Where can windows sit near a suite's exit door?
Not within 3 m (9 ft 10 in) of it at a tight corner, unless the glass is protected. When one unit's exterior exit door is within 3 m horizontally of the other unit's unprotected openings, and the two walls meet at an exterior angle of less than 135°, those openings need wired glass in fixed steel frames or glass block (NBC(AE) 2023, 9.9.4.6). On a flat wall, where the walls don't meet at a corner, the rule doesn't bite.
The diagram puts the 3 000 mm and 1 200 mm distances side by side at the same scale.
The distances, as of October 2026:
| Situation | Distance that triggers the rule | What the code asks | Clause |
|---|---|---|---|
| Exterior exit door near the other unit's window, walls meeting at under 135° | Within 3 m (9 ft 10 in) horizontally | Wired glass in steel frames or glass block | 9.9.4.6 |
| Unenclosed outside stair that is a suite's only way out | Openings within 3 m horizontally and less than 10 m (32 ft 10 in) below or 5 m (16 ft 5 in) above it | Wired glass in steel frames or glass block | 9.9.4.4 |
| Openings of the two units on walls meeting at 135° or less | Under 1.2 m (3 ft 11 in) apart | Keep them at least 1.2 m apart | 9.10.12.3 |
Note: code distances, applied by the City of Calgary at plan review. Wired glass in fixed frames doesn't open, so it can't fix a bedroom's egress window.
Calgary's Building Advisory B23-012, dated 5 March 2026, says stairs and ramps 600 mm (2 ft) or less above the ground beside them aren't unenclosed exterior exit stairs for this rule, and accepts a fire shutter as another way to protect an opening (The City of Calgary, B23-012). The City says its advisories have no legal status.
How do smoke and CO alarms connect in a house with a suite?
Across the whole house. Smoke alarms in a house with a secondary suite must be wirelessly interconnected or hard-wired so that any one sets off all of them, in both units (NBC(AE) 2023, 9.10.19.5). Carbon monoxide alarms work the same way: one sounding makes all of them sound (NBC(AE) 2023, 9.32.3.9).
The City of Calgary's suite page asks for alarms permanently wired to the panel, interconnected so the suite's alarms sound with "a minimum of one smoke alarm" in the main home (The City of Calgary, 2026). The code's wording is wider, so plan for every alarm in the house to sound together. Where each alarm goes, room by room, is on the smoke and CO alarm guide.
What sound separation does a secondary suite need?
Less than between apartments, which need an apparent sound transmission class (ASTC) rating of 47 or a sound transmission class (STC) rating of 50. A house with a secondary suite can use any of three lighter options (NBC(AE) 2023, 9.11.1.1):
| Option | What it takes | Clause |
|---|---|---|
| Prescribed build-up | Joist spaces filled with at least 150 mm (5.9 in) of sound-absorbing material, stud spaces filled, resilient channel at 400 or 600 mm (1 ft 4 in or 2 ft) on centre on one side, and 12.7 mm (0.5 in) gypsum on ceilings and both sides of walls | 9.11.1.1.(2)(a) |
| Tested assembly | STC rating of at least 43 | 9.11.1.1.(2)(b) |
| Whole path | ASTC rating of at least 40, separating assembly and adjoining construction together | 9.11.1.1.(2)(c) |
Note: minimum sound ratings; a quieter suite is a design choice. The Note explains the lower bar: each household hears only one other unit, and often the owner decides how much protection to add (NBC(AE) 2023, Note A-9.11.1.1.(2)). The resilient channel also lowers the finished ceiling by its own depth, which matters in a basement near the 1.95 m minimum.
What else does the code ask of the suite itself?
Every dwelling unit with piped water needs a kitchen sink, a lavatory, a bathtub or shower, and a water closet (NBC(AE) 2023, 9.31.4.1). Ceilings must be at least 1.95 m (6 ft 5 in), or 1.85 m (6 ft 1 in) under beams and ducting (NBC(AE) 2023, 9.5.3.1). Every bedroom needs an escape window, covered on the egress window guide.
Calgary asks for one structural item the code doesn't spell out here: a new exterior exit stairwell needs a shallow foundation designed by a registered professional engineer, because digging it out cuts into the frost cover (The City of Calgary, 2026). The zoning, permit and cost side of a suite is in the legal basement suite guide.
Seeing the suite plan at full size
At 1to1 Plans Calgary, your basement plan is shown at full size on a walkable LED floor, with room names and dimension lines. You can stand at the foot of a shared stair and see which doors open onto it and whether the exit path passes the service room. Changes are shown on the floor right away.
Sessions are quoted for the plan, and the quote is free (see pricing). See renovations and suites, the other building code guides, or book a session.
Questions
Does a basement suite need a fire-rated wall in Alberta?
No. In Alberta, a basement suite in a house with a secondary suite can use a continuous smoke-tight barrier of 12.7 mm (0.5 in) gypsum board instead of a fire-rated separation, on both sides of the walls and under the floor framing, as of October 2026. The joints must be taped and filled so smoke can't pass.
What kind of door is required between a basement suite and the house?
In Alberta, a door between a basement suite and the main house, or onto a shared stair, must be solid-core wood at least 45 mm (1.8 in) thick with a self-closing device. The code's Note says it doesn't need a fire-door label.
Does the furnace room need drywall in a house with a suite?
Yes. In Alberta, a furnace or water heater serving both units in a house with a secondary suite must sit in a service room lined with 12.7 mm (0.5 in) gypsum on both sides of its walls and under its ceiling framing. Its door follows the same 45 mm self-closing rule.
Do smoke alarms in a basement suite have to connect to the main house?
Yes. In Alberta, smoke alarms in a house with a secondary suite must be hard-wired or wirelessly interconnected so any one alarm sets off every alarm in both units. Carbon monoxide alarms in the house must be wired the same way.
Sources
- NBC(AE) 2023, 9.10.9.16 nrc-publications.canada.ca
- Government of Alberta, 2026 alberta.ca
- The City of Calgary, 2026 calgary.ca
- The City of Calgary, 2026 calgary.ca
- The City of Calgary, B23-012 calgary.ca
