In Alberta, a loft can be left out of a house's storey count if it covers no more than 40% of the open area of the room it sits in and stays open above, with no partitions over 1 070 mm (3 ft 6 in) (NBC(AE) 2023, 9.10.4.1). Separately, any level more than one storey from a door out of the home needs an openable window at least 1 m (3 ft 3 in) high and 0.55 m (1 ft 10 in) wide, or a balcony (NBC(AE) 2023, 9.9.9.1). Both rules are in the second printing of the 2023 Alberta Edition, in force since 17 August 2026 (Government of Alberta, 2026).
Key takeaways
- As of October 2026, Part 9 of Alberta's code, the part written for houses, covers buildings of no more than 3 storeys in building height and 600 m² (6,458 sq ft) in building area (NBC(AE) 2023, Division A, 1.3.3.3).
- A mezzanine is left out of building height if it covers no more than 40% of the open area of its room, with no partitions over 1 070 mm (3 ft 6 in) and an enclosed part of no more than 10% (NBC(AE) 2023, 9.10.4.1).
- A second mezzanine level stacked over the first always counts as a storey (NBC(AE) 2023, 9.10.4.2).
- A level more than one storey from an exit door needs a window opening at least 1 m by 0.55 m with its sill no more than 1 m above the floor and 7 m (23 ft) above the ground, or a balcony (NBC(AE) 2023, 9.9.9.1).
- Under a sloped ceiling, a bedroom needs 2.1 m (6 ft 11 in) of height over at least 3.5 m² (37.7 sq ft), touching the entry, and a living space needs it over 10.0 m² (107.6 sq ft) (NBC(AE) 2023, 9.5.3.1 and Table 9.5.3.1).
Why does it matter whether a loft counts as a storey?
Because the house rules in Part 9 stop at 3 storeys. Part 9 applies to residential buildings of 3 storeys or less in building height, with a building area of no more than 600 m² (6,458 sq ft) (NBC(AE) 2023, Division A, 1.3.3.3). Building height counts the storeys between the roof and the floor of the first storey, and the first storey is the highest one whose floor is no more than 2 m above grade (NBC(AE) 2023, Division A, 1.4.1.2).
On a three-storey infill, a loft at the top would be a fourth storey if it counted. The mezzanine rules let it stay part of the room below. The code defines a mezzanine as an intermediate floor between the floor and ceiling of a room or storey, including an interior balcony.
When is a loft a mezzanine instead of a storey?
When it passes one of two tests in 9.10.4.1 (NBC(AE) 2023, 9.10.4.1). The first is a small-area test: no more than 10% of the building's floor area, and no more than 10% of the suite's area on that storey. The second is the one lofts usually use:
These are the conditions under the open-room test, as of October 2026:
| Condition | Limit | Clause |
|---|---|---|
| Loft area | No more than 40% of the open area of the room it sits in | 9.10.4.1.(2) |
| Space above the loft floor | Open, with no partitions or walls higher than 1 070 mm (3 ft 6 in) | 9.10.4.1.(2) |
| One closed room on the loft | Up to 10% of the room's open area, without blocking the view between the loft and the room | 9.10.4.1.(3) |
| A second loft level above the first | Counts as a storey | 9.10.4.2 |
| Floor area for occupant load | The loft's area is added to the storey below | 9.10.4.1.(4) |
Note: these decide building height only. They don't make a loft exempt from the egress, ceiling or guard rules below. The City of Calgary rules on how a particular loft is counted.
The 40% is worked from the open floor area of the room. The code's Part 3 note on mezzanine area says any enclosed space under the mezzanine comes off the total first, so a powder room tucked under the loft shrinks the allowance (NBC(AE) 2023, Note A-3.2.1.1.(3)(a)).
The drawing works the numbers for a double-height room 5 000 mm by 4 000 mm (20 m², 215 sq ft) with nothing enclosed below. A loft 2 000 mm deep across the 4 000 mm side covers 8 m², the full 40%, and up to 2 m² of it can be a closed room.
Does a third-floor loft need an escape window?
Usually, yes. Inside a home of more than one storey, you shouldn't have to go up or down more than one storey to reach a level with a way out: an exit door no more than 1.5 m (4 ft 11 in) above the ground outside, or an egress door to a public corridor, an enclosed exit stair or an outside passageway (NBC(AE) 2023, 9.9.9.1). In a typical house, the front door is on the main floor, so the upper floor is fine and a third level is one storey too far.
That third level has two ways to meet the rule:
| Option | What the code asks for | Clause |
|---|---|---|
| An escape window | Opens to at least 1 m (3 ft 3 in) high and 0.55 m (1 ft 10 in) wide, with a sill no more than 1 m above the floor and no more than 7 m (23 ft) above the ground | 9.9.9.1.(2) |
| A balcony | Direct access from that level to a balcony | 9.9.9.1.(3) |
Note: the window option is only open to a home that isn't above or below another suite. In a house with a basement suite, the upper home is above another suite, so plan on the balcony or a real exit, and confirm with the City of Calgary.
The code doesn't say whether a loft that passes the mezzanine test still counts as a storey for this travel limit. The mezzanine rule is written for building height. Plan for the window or balcony unless the City tells you otherwise.
The escape window is bigger than a bedroom's. A bedroom window needs only 0.35 m² (3.8 sq ft) with no side under 380 mm, and the code's note draws that as a 592 mm (1 ft 11 in) square (NBC(AE) 2023, 9.9.10.1 and Note A-9.9.10.1.(2)). The upper-level window needs 1 m by 0.55 m.
A loft bedroom needs an escape window too. A bedroom open to another area can be treated with it as one combination room if the opening between them is at least the larger of 3 m² (32.3 sq ft) or 40% of the wall, and there must be direct passage between the two (NBC(AE) 2023, 9.5.1.2). The note explains the direct passage: it keeps the escape window reachable. The egress window guide covers bedroom windows.
How much ceiling height does a room under a sloped roof need?
The code sets a 2.1 m (6 ft 11 in) ceiling over a minimum area for each room type, and that area has to be contiguous with the room's entry (NBC(AE) 2023, 9.5.3.1.(4)). Outside that area, the table sets no minimum height.
These are the areas that need 2.1 m in an attic room or loft, as of October 2026:
| Room or space | Area that needs 2.1 m (6 ft 11 in) | Clause |
|---|---|---|
| Living room or space, such as a loft family room | The whole space, or 10.0 m² (107.6 sq ft) if smaller | Table 9.5.3.1 |
| Master bedroom | The whole space, or 4.9 m² (52.7 sq ft) if smaller | Table 9.5.3.1 |
| Other bedroom | The whole space, or 3.5 m² (37.7 sq ft) if smaller | Table 9.5.3.1 |
| Bathroom above grade | The whole space, or 2.2 m² (23.7 sq ft) if smaller | Table 9.5.3.1 |
| Hall or passage | All of it | Table 9.5.3.1 |
Note: minimum heights over a minimum area, measured between finished surfaces. The basement ceiling height guide covers the rules for suites and basements.
The contiguous rule is the one that catches attic rooms. If the full-height strip runs along the ridge but the door is in a low knee wall, the 2.1 m area doesn't touch the entry. Put the door where the ceiling is tallest.
The low spaces behind a knee wall can trigger an attic hatch. Any attic or roof space with an open area of 3 m² (32.3 sq ft) or more, at least 1 m in length or width and at least 600 mm (2 ft) high, needs a hatch. For one home, that hatch can be 0.32 m² (3.4 sq ft) with no side under 500 mm (1 ft 8 in) (NBC(AE) 2023, 9.19.2.1).
What else does a loft need?
A guard, a way up, and a check with the City. The open edge of a loft inside a home needs a guard at least 900 mm (2 ft 11 in) high, with openings that stop a 100 mm (3.9 in) sphere. If the drop to the floor below is more than 4.2 m (13 ft 9 in), the guard can't be climbable between 140 mm and 900 mm (NBC(AE) 2023, 9.8.8.3, 9.8.8.5 and 9.8.8.6). The guard height guide has the detail.
A spiral stair can be the only way up to a loft that serves no more than 3 people, though never as an exit (NBC(AE) 2023, 9.8.4.7). The winder and spiral stair guide covers its dimensions.
Calgary's Land Use Bylaw sets its own height limits, separate from the code's storey count. Its additions page lists an upper-floor addition under 10 m² (108 sq ft) that stays below the existing roof height among the common cases that fit the bylaw; a loft that raises the roof is past that line (The City of Calgary, additions). The Calgary building permit guide explains when a development permit comes in.
What does a walkthrough show for a loft?
A loft is hard to judge on paper because it's a floor plan on top of a room you also need to see. At the studio, the LED floor shows one level at full size at a time, so you can walk the room below, then the loft over it, and see how much of the room stays open. The section and elevations go up on the wall-size screen, where the sloped ceiling and the full-height strip are easier to read. Changes are made on the spot.
You keep the recording of the session. Sessions are quoted for your plan, with nothing to pay at booking (how quotes work). Read the other building code guides, see how builders use the studio, or book a session.
Questions
Is a loft considered a storey in Alberta?
A loft in Alberta isn't counted in building height if it covers no more than 40% of the open area of the room it's in, stays open above with no partitions over 1 070 mm (3 ft 6 in), and has no second loft stacked above it. The City of Calgary decides how a particular loft is counted.
Can you build a three-storey house in Alberta?
Yes: Part 9 of Alberta's building code covers houses of up to 3 storeys in building height and 600 m² (6,458 sq ft) in building area. Calgary's Land Use Bylaw sets its own height limits for each district, so check those as well.
Does a third floor need a fire escape window in Alberta?
In Alberta, a level more than one storey from an exit door needs an openable window at least 1 m (3 ft 3 in) high and 0.55 m (1 ft 10 in) wide, with its sill no more than 1 m above the floor and 7 m (23 ft) above the ground, or direct access to a balcony. The window option isn't available to a home above or below another suite.
What ceiling height does an attic bedroom need in Alberta?
An attic bedroom in Alberta needs a ceiling of at least 2.1 m (6 ft 11 in) over 3.5 m² (37.7 sq ft), or 4.9 m² (52.7 sq ft) for a master bedroom, and that area must connect to the doorway. The rest of the room can be lower.
How big does an attic hatch need to be in Alberta?
In a single home in Alberta, an attic hatch can be 0.32 m² (3.4 sq ft) with no side under 500 mm (1 ft 8 in). Elsewhere it must be at least 550 mm by 900 mm (1 ft 10 in by 2 ft 11 in).
Sources
- NBC(AE) 2023, 9.10.4.1 nrc-publications.canada.ca
- Government of Alberta, 2026 alberta.ca
- The City of Calgary, additions calgary.ca
