Date of Publication: March 30, 2026 [2026.03.V-01.C]
Subject: Egress from Mezzanines
2024 Ontario Building Code Reference(s):
Article 1.4.1.2 of Div. A Definitions
Sentences 3.2.1.1.(3) and (4).
Article 3.4.1.4. of Div. B.
Article 3.4.2.1. of Div. B.
Article 3.4.2.2. of Div. B.
Article 3.4.2.4. of Div. B.
Incoming Request:
“A Group A2 occupancy (Banquet Hall) is proposed in a two storey, new Group D Major occupancy building. In the unit, overlooking the main entrance lobby within the unit, we are proposing a closed mezzanine that is greater than 10% of the floor area of the suite, (hence the two- storey classification) with an occupant load of 45.
Is the mezzanine permitted to egress via an unenclosed stair to the main floor area and exit through the lobby per 3.4.4.2.”
Executive Summary:
Per the 2024 OBC, the default egress requirement for mezzanines is “...exit(s) accessible at the mezzanine level...”. Permission to egress using an open stair is generally limited to mezzanines that do not require termination at a fire separation, have an area less than 500m2, and an occupant load of 60 or less, however they are subject to travel distance requirements.
Discussion & Considerations:
The 2024 OBC has been updated to harmonize with the National Building Code (NBC) and most other provinces. Mezzanine egress requirements have been consolidated into Article 3.4.2.2.. Since the floor area in question fits the definition of mezzanine, (...an intermediate floor assembly between the floor and ceiling of any room or storey...), analysis begins at Article 3.4.2.2..
Sentence 3.4.2.2.(1). States the general rule, that “...the space above a mezzanine shall be served by means of egress leading to exits accessible at the mezzanine level on the same basis as floor areas.”. Generally speaking, this means 2 enclosed exit stairs meeting the requirements
of 3.4.2.1. that lead to a separate building or an exterior open space. An exterior doorway, an enclosed ramp, a horizontal exit, etc (per Article 3.4.1.4.) would also be acceptable, provided it is accessible at the mezzanine level.
Sentences 3.4.2.2.(2)(a) to (d) provide exemptions to Sentence (1), and permit open stairs from a Group A, Div 2 mezzanine if ALL the conditions are met:
- Mezzanine is not required to terminate at a vertical fire separation based on Sentence 3.2.8.2.(1) [is not considered a storey per Sentence 3.2.1.1.(3) or (4)];
- Restriction on the number of occupants, [Max OL of 60];
- Size of the mezzanine is relatively small, [Max 500m2]; and
- Limitation on the travel distance – based on the number of doorways.
Sentence 3.4.2.2.(3). permits ½ of the required egress to be an open stair. This exemption would be used if all conditions in 3.4.2.2.(2) cannot be met. The only condition for this exception is:
- The mezzanine is not required to terminate at a vertical fire separation based on Sentence 3.2.8.2.(1)
Note: Group A, Division 1 and 3 plus Group B major occupancies are treated differently by Article 3.2.8.2. than other occupancies, and as a result have different mezzanine egress requirements.
Egress Requirements:
Since the mezzanine in question is in a Group A, Division 2 occupancy, is closed and is more than 10% of the suite in which it is located, it is required to terminate in a fire separation [does not comply with Sentences 3.2.1.1.(3) or (4)], which disqualifies it from either exemption above. Exits are therefore required at the mezzanine level (one or two, depending on the number of exits required per Article 3.4.2.1.) If enclosed exit stairs are used, they must lead to a separate building or an open exterior space per the definition of an exit.
Exiting through a lobby:
One of the enclosed exit stairs would be permitted to discharge into the lobby area (“exit through a lobby”), provided all of the conditions in 3.4.4.2 are met, which includes all requirements for exits (in particular 3.4.4.4.), minus the specific exemptions. It should be noted that unenclosed stairs from a mezzanine to a lobby is not the same as “exiting through a lobby” as described in Article 3.4.4.2.
Risk/Benefit Analysis:
Where a building contains a mezzanine, the greatest risk is to those on the upper level, as smoke may rise and affect them before those on the lower level. If a fire originates on a lower
level, it may also be difficult for someone on the upper level to see the safest egress path. This is reflected in the egress requirements. The basic principle is that a small open mezzanine (where occupants would be aware of hazards in the space below) may be treated as part of the floor area below it for egress purposes, but a larger, and/or enclosed mezzanine (less awareness of the space below) will usually require separate exits.
Final Recommendation:
In the scenario described, an enclosed exit is required to lead from the mezzanine level to another building or the exterior. Alternatively, an enclosed exit stair would be permitted to discharge through the lobby only if it met all of the requirements of Article 3.4.4.2.. This recommendation is based on the limited information supplied. Changes to the design parameters may change the recommendation.
Recommendation to Ministry of Municipal Affairs and Housing:
None at this time
Referenced Document(s):
2024 Ontario Building Code (OBC) O. Reg. 163/24 amended to O.Reg 5/25
Disclaimer:
This guidance document is intended to assist building officials by gathering relevant information to interpret the OBC Act and the prescriptive requirements of the Ontario Building Code, and is intended to be a best practice aid for building officials.
The views expressed within this guidance document should not be considered as the official interpretation of legislated requirements based on the Ontario Building Code, as the final responsibility for interpretation rests with the local Authority Having Jurisdiction.
The views of this advisory committee should not be construed as legal advice.