It has been reported that stair users are likely to miss a step once in every 2,222 occasions they use stairs, suffer a minor accident once in every 63,000 uses, a painful accident once in every 734,000, and need hospital attention once every 3,616,667 uses. To put your mind at ease, the probability of hospitalization is about 1 in 1000 years.¹

Stair accidents result in many injuries and financial losses each year in Canada and the US. A 2017 study in the US reported over a million stair-related injuries are treated in emergency departments every year.² According to a Health Canada report, about 13% of fall-related injuries to seniors over 65 years old occur when ascending or descending stairs.³ Falling on stairs can also be fatal. Falls on stairs are the second most common cause of accidental death in the US after car accidents.¹ Seniors over 65 are disproportionately affected because they are both at higher risk of falling on stairs and more likely to suffer severe injuries. Seniors account for about 70% of deaths from stair accidents.⁸

Stair-related accidents take a large financial toll on societies. The societal economic cost of stair-related accidents includes medical costs, loss of quality of life and loss of productivity. The societal cost of stair-related injuries in the US is estimated to be $100 billion a year.¹ In Canada, this figure was estimated to be $19.8 billion in 2004.³

If the design or construction of the stairs violates the local building code, the designer or builder could be held liable for any injuries or damages resulting from the use of the stairs. In this article, the key requirements of the Ontario Building Code (OBC) are discussed.⁶

1. Design Principles for Stairs in the Ontario Building Code

Stair design requirements in building codes can be generally grouped into two main criteria: ergonomics and safety. Ergonomics indicate that people who fall within a reasonable range of height and physical ability should be able to use stairs without difficulty. For example, the run and rise of each step should be compatible with the normal stride of an average person. If the run of the step is too deep or the rise is too high, one must lengthen their stride beyond the normal level, resulting in increased fatigue.

The purpose of safety criteria is to minimize the risk of falling when using the stairs. For example, treads should not be slippery, and the run and rise of steps should be uniform such that one does not trip while using the stairs. There should be a reachable, graspable handrail for the stair user to hold onto, if needed, in order to keep their balance. Furthermore, the handrail should be at a proper height. A lower handrail requiring the stair user to bend to grab it forces the body’s center of mass forward, which is dangerous when descending. A higher handrail is inconvenient to grab and takes a longer time to reach in case of a fall incident.

2. Ontario Building Code Requirements: Key Definitions

There are three frequently used terms in the OBC⁶ that describe dimensional requirements for steps: rise, run and tread depth (illustrated in the figure below). Rise is measured as the vertical distance between adjacent steps or walking surfaces. Run is the horizontal nosing-to-nosing distance. Tread depth is the horizontal distance measured from nosing to riser and is typically one inch deeper than the run. For spiral stairs, the terminology, minimum average run, and minimum run are used to describe the angled shape of the steps.

OBC refers to three types of stairs:

• Service & Mezzanines in live/work units, that serve service rooms or spaces and mezzanines not exceeding 20 m² (215 ft²) in live/work units,
• Private stairs, that are within dwelling units or serve a single dwelling unit or a garage that serves a single dwelling unit, and
• Public stairs, which are any stairs not described above.

2.1. Rise and Run of Stairs

As mentioned earlier, the run and rise of the steps should be compatible with the natural stride of an average person to minimize the safety risk of using the stairs and optimize the energy expended by the user. Stair climbing demands a higher rate of energy expenditure than any other routine activity and is comparable to performing heavy labour.⁷ However, climbing very steep stairs is as fatiguing as climbing very low-pitch stairs,⁷ thus the slope of the stairs should be within an optimal range for ease of use. The slope of the stairs is determined by the combination of the run and rise of the steps. Treads should also be deep enough to provide a proper landing for the foot.

The OBC 2012⁶ requires a minimum of three risers in interior stairs of any building other than dwelling units; in dwelling units, the stairs can have less than two risers. The OBC requirements for the run and rise of rectangular stairs are given in Table 9.8.4.1 of OBC 2012. In this Table, private stairs are those within dwelling units or serving a single dwelling unit. As given in this table, for private stairs, the rise should be between 125 mm (5 in.) and 200 mm (8 in.), and the run should be between 210 mm (8¼ in.) and 355 mm (14 in.). Based on these requirements, the slope of a stair flight for a private stair should be between 19⁰ and 43⁰.

Studies with light modelling have shown that bevelled edges on nosing make the tread more visible.⁶ However, the sloped portion of the nosing should not be too wide in order to reduce the risk of slipping. Moreover, too much projection of the nosing could increase the risk of tripping. Therefore, the OBC limits the width of curved or bevelled edges to 25 mm (1 in.) and requires that the leading edge not reduce the minimum tread depth by more than 15 mm (5/8 in.).

In order to bring the OBC into agreement with other Canadian building codes, changes to the dimensional requirements are planned for 2022, some of which are summarized below. One of the noteworthy changes is the increase in the minimum run from 210 mm to 255 mm for private stairs. Tread depth will be required to be no less than the run dimension, and not more than the run plus 25 mm. This change is aimed at reducing incidents on descent, which tend to be more serious.⁹ Research has shown that the risk of an accident on descent is greatly diminished when the tread is larger than the user’s foot.⁷

2.2. Nosing dimensions

Studies with light modelling have shown that bevelled edges on nosing make the tread more visible. However, the sloped portion of the nosing should not be too wide in order to reduce the risk of slipping. Moreover, too much projection of the nosing could increase the risk of tripping. Therefore, the OBC 2012 limits the width of curved or bevelled edges to 25 mm (1 in.) and requires that the leading edge not reduce the minimum tread depth by more than 15 mm (5/8 in.).

2.3. Dimensional uniformity between steps

The most important geometric factor behind many falls on stairs is the dimensional consistency between treads.⁷ If either the rise or the tread varies from one step to the next, then the risk of accidents increases dramatically. Researchers have determined that stair users typically make an unconscious and automatic evaluation of step dimensions within the first step or two. Think of it as your brain generating a mental model of the entire flight of stairs from just the first one or two steps.

When the physical stairs are inconsistent with the mental model your brain created, you can experience a misstep, and potentially a fall.⁵ This is why dimensional consistency is very important in the design and construction of safe stairs.

To improve the safety of spiral and angled stairs, the OBC requires risers and treads to have uniform dimensions, where risers can vary by no more than 5 mm (3/16 in.) between adjacent risers and no more than 10 mm (3/8 in.) between the tallest and shortest risers in a flight. Similarly, treads can vary by no more than 5 mm (3/16 in.) between adjacent treads and no more than 10 mm (3/8 in.) between the deepest and shallowest treads in a flight.

2.4. The type of finishes

To minimize the risk of slipping and tripping when using stairs, the OBC requires the treads and landings to be wear-resistant, slip-resistant, even, and free from defects. In a dwelling unit, the following landing and stair finishes are acceptable by the OBC: hardwood, vertical grain softwood, resilient flooring, low pile carpet, matte finish ceramic tile, concrete, and plywood (for stairs to garages and unfinished basements). In buildings other than dwelling units, treads and landings of interior and exterior stairs should have a slip-resistant finish or be provided with slip-resistant strips that extend less than 0.04″ (1.0 mm) above the surface.

One of the causes of trip and fall accidents on stairs is poor visibility of the edges of treads and landings. Poor visibility causes users to misread the edge of a step and trip. One of the best ways to improve the visibility of the edges is colour contrast. In single dwelling units, the OBC requires all stairs, except in service rooms and spaces, to utilize either a contrasting colour or a distinctive pattern to demarcate the leading edges of treads and landings.

2.5. Handrails and their supports

Handrails are intended to provide guidance and support to the stair user and to arrest falls.

To enhance safety when using stairs, there should be at least one handrail on the side of the stairs to provide support and guidance to the user. In a dwelling unit, the OBC requires that at least one side of any staircase be equipped with a graspable handrail that is continuous for the length of the stairs, except where interrupted by doorways, landings, or posts where stairs change direction. Continuous handrails are important because visually impaired individuals rely on handrails for directional cues and individuals with impaired mobility rely on handrails for support. Discontinuous handrails force the user to release and then re-grasp the handrail along the length of the stairs, putting them at increased risk of a fall.¹¹

Researchers have studied the effect of size and shape of handrails on their grasp-ability and stabilizing effect on the handrail user. Studies have shown that round handrails 1.5″ in diameter gave the most stabilizing force to the handrail user, while vertical rectangular and decorative handrails generated the least stabilizing force.⁷ This is because fingers can easily wrap around a round handrail, creating a power grip, while a vertically rectangular or decorative handrail can only be partially grasped by hands, creating a pinch grip. A handrail should either have an under-surface or a relatively deep finger purchase so that users can grasp the rail firmly and comfortably¹⁰.

In a single dwelling unit, no handrail is required for interior stairs with less than two risers, or for exterior stairs with less than three risers. Handrails must be placed at 865–965 mm (34–38 in.) height and have a minimum clearance of 50 mm (2 in.) from any wall surface behind it. Handrails (including their supports) are not permitted to project more than 100 mm (4 in.) into the required stair width.

Handrails and their attachments should be strong enough to help the user keep their balance. Therefore, OBC 2012 requires that handrails and their attachments shall be designed to resist a minimum 0.9 kN (200 lbs) applied anywhere on the handrail. For a handrail serving a single dwelling unit, this load requirement for handrail attachments is considered to be met if the attachments are spaced a maximum 1200 mm (4 ft) apart and fastened to studs or solid blocking with at least two wood screws penetrating a minimum 32 mm (1¼ in.) into solid wood.

A minimum of two side handrails is required for spiral stairs in non-residential buildings. An additional handrail between the side ones may also be required if the stairs are wider than 2200 mm (86½ in.). The minimum required width of stairs in a non-residential building depends on the occupant load. The middle handrail must be placed such that no position on the stairs is farther than 825 mm (32½ in.) from a handrail. This is to ensure that all people using the stairs can reach at least one handrail. If the handrail is too far from the user then they will be unable to reach it if they stumble.

To provide support and guidance for users as they enter and exit the stairs, at least one side handrail needs to extend a minimum of 12″ (300 mm) horizontally beyond the top and bottom of the stairs. Handrail extension is not required for a single dwelling unit since the residents of the unit are familiar with their surroundings. Table 9.8.7.1. of the 2012 OBC gives the number of sides of a stair required to be equipped with a handrail.

Summary

Falls on stairs cause a lot of injuries and deaths in the US and Canada, and result in enormous medical costs. One of the major risk factors in stair-related injuries is the design of the stair elements, mainly handrails, run and rise of stairs. Building codes in different jurisdictions in Canada have slightly varied requirements for stairs, but the objective of all building codes is to reduce the probability of stair-related accidents. This article briefly navigated key requirements of the 2012 edition of the Ontario Building Code. If a stair-related injury is proven to be the result of poor design, the designer and builder of stairs can be held liable for not following the requirements of the building code.

Nabi Goudarzi, Ph.D., P.Eng.

Nabi specializes in the forensic structural investigation of buildings and the design of retrofitting schemes for damaged or under-designed structures. In the course of his career, Nabi has conducted structural assessments of existing steel, concrete, masonry and wood buildings under gravity loading, vibration and seismic forces. He has also designed steel and concrete structures, including high-rise residential and office towers, commercial retail units, and long-span steel trusses. Nabi holds a MSc. in Earthquake Engineering from Sharif University of Technology and a Ph.D. in Structural Engineering from the University of Alberta.

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