Understanding Ontario's Exit Stair Requirements and the Ongoing Debate
Ontario exit stair requirements continue to play a critical role in shaping the design and feasibility of mid-rise residential development across the province. As Ontario faces sustained housing supply and affordability pressures, mid-rise residential buildings, typically four to six storeys, are increasingly recognized as an important building form. These buildings offer higher density than low‑rise housing while remaining compatible with established urban neighbourhoods.
A key regulatory factor influencing mid-rise design is the Ontario Building Code exit stair requirement, which generally mandates two enclosed exit staircases for buildings of this scale. While these exit stair requirements are intended to support life‑safety objectives, they also have significant implications for building efficiency, construction cost, floor plate design, and achievable unit layouts. As other jurisdictions re‑examine single‑stair models and new research emerges, the debate around one staircase versus two staircases in Ontario has become a growing focus within the development, design, fire protection and code‑consulting community.
Current Regulatory Framework in Ontario
Under Part 3 of the Ontario Building Code, residential buildings exceeding two storeys generally require a minimum of two exits from each floor area (Article 3.4.2.1). In practice, this translates into two exit stair shafts serving most mid-rise apartment buildings. Single exit designs are permitted only in limited circumstances, such as low buildings (i.e. two storeys or less) or specific non-residential occupancies.
The intent of the two-exit requirement is redundancy: if one exit becomes compromised due to fire or smoke, occupants retain access to an alternative path of egress. This approach has long been a foundational principle of building and fire codes, particularly in North America, and continues to be viewed as a conservative life safety measure.
However, the application of this requirement alongside modern building systems, including full sprinkler protection, enhanced alarm and detection systems, and improved fire-resistant construction, has prompted renewed examination of whether prescribed exit counts always represent the most proportionate response to risk.
Design and Development Implications
Requiring two exit staircases has several practical impacts on mid-rise residential design. Stair enclosures occupy a significant portion of a building’s gross floor area, often driving longer corridors, reduced façade exposure for residential units, and increased complexity in structural and mechanical layouts.
From a development perspective, these impacts can translate into higher construction costs and reduced efficiency. Studies examining compact residential buildings (i.e. small footprint and floor areas) have found that eliminating a second stair in qualifying conditions can reduce both circulation space and overall floor area requirements. While the magnitude of these impacts varies by project, they are frequently cited as factors influencing unit mix, market feasibility, and building massing.
At the same time, proponents of the current approach emphasize that prescriptive rules provide clarity and consistency, reducing reliance on project specific performance analysis and Alternative Solutions.
Approaches in Other Jurisdictions
Several jurisdictions in Canada and internationally have introduced or are evaluating alternative exit stair approaches for mid-rise residential buildings.
- British Columbia amended its Building Code in 2024 to permit single-stair residential buildings up to six storeys, subject to a set of conditions including sprinkler protection, limitations on floor area, maximum travel distances, and enhanced smoke control measures.
- National Building Code of Canada (NBC) committees are currently reviewing proposals related to single egress mid-rise buildings, informed by international precedents and research into fire safety outcomes.
- Municipal studies, including work undertaken by the City of Toronto in 2024, have evaluated the feasibility of limited single exit configurations, although no local code changes have yet been adopted.
- Alternative Solutions, including performance-based fire engineering analyses, have been applied in cities such as Edmonton to support single stair designs on a project-by-project basis.
Internationally, many European jurisdictions and selected U.S. cities permit mid-rise single stair residential buildings, often under codes that rely more heavily on fire compartmentation, suppression, and smoke management strategies than on multiple exits.
Safety Considerations
Life safety is the primary concern in discussions about exit stair requirements. A key issue with single‑stair buildings is the risk of losing the only escape route if the stairwell is affected by a fire. Firefighting in buildings with just one stairwell is often regarded as more dangerous than in buildings with two exits, as evacuation and fire suppression efforts can conflict. Firefighters carrying heavy equipment up the stairwell are likely to encounter occupants trying to escape, which can slow response times and delay rescues. If the stairwell becomes unusable, occupants may be trapped and firefighters are left with very limited options, significantly increasing the risk to life.
Recent studies, including research by the Pew Charitable Trusts, have reviewed fire incident data from jurisdictions where single‑stair residential buildings are common. These studies suggest there is limited evidence of increased risk when such buildings are equipped with robust fire protection systems. However, building officials and fire services continue to stress that acceptable risk levels depend on local conditions, including emergency response capacity, enforcement practices, and overall risk tolerance.
Where single stair buildings are permitted, they are typically subject to additional safeguards, such as:
- Full NFPA 13 sprinkler systems
- Fire rated and pressurized stair enclosures
- Enhanced smoke detection and alarm systems
- Strict limits on building height, floor area, and travel distance
These requirements are intended to mitigate reliance on a single egress path and to maintain tenable conditions during evacuation.
The discussion around single‑exit residential buildings benefits from this kind of evidence‑based caution and operational insight. Recent NRC research highlights gaps in the existing literature, particularly related to firefighting operations, system redundancy, and real‑world occupant behaviour, which remain important considerations in evaluating alternative egress models. Addressing these gaps will require ongoing, multidisciplinary engagement as jurisdictions consider potential next steps.
Policy Context in Ontario
Ontario’s recent planning policy changes, including Regulation 462/24 under the Planning Act, reflect an increased emphasis on housing supply and flexibility, particularly for low‑rise residential forms. While these reforms focus primarily on zoning and land use permissions rather than building safety regulations, they have prompted broader discussion about the alignment between planning objectives and technical code requirements.
Some stakeholders have suggested that a review of exit stair provisions could form part of a longer-term examination of mid-rise housing delivery. Others caution that building code changes require extensive technical review and consensus to ensure consistent safety outcomes across the province.
Ongoing Industry Discussion
The question of exit stair requirements sits at the intersection of architecture, fire protection engineering, development economics, and regulatory policy. Architects and housing advocates often highlight design efficiency and affordability considerations, while building officials and fire authorities prioritize effectiveness, reliability, and clarity of life safety provisions.
Most participants agree that any potential changes would need to be evidence based, clearly scoped, and supported by enforceable performance criteria. Options discussed in other jurisdictions include pilot programs, expanded use of Alternative Solutions, or incremental code amendments tied to specific building parameters.
Conclusion
Exit stair requirements for mid-rise residential buildings remain an evolving area of policy and technical review. Ontario’s current two exit approach reflects longstanding life safety principles, while developments elsewhere demonstrate how alternative models can function under defined conditions.
As housing demand continues to place pressure on urban development models, ongoing evaluation of building code provisions—including exit stair requirements—may help inform future updates. Any adjustments would need to balance safety objectives with design efficiency, cost considerations, and regulatory consistency, supported by research, stakeholder engagement, and careful implementation.