Mind Your Step: Looking at Stair Construction in Slip-and-Fall Accidents
June 17, 2022
Slip-and-fall accidents have a substantial economic and social impact. According to the British Columbia Injury Research and Prevention Unit, about 8% of 2017 hospitalizations were due to stair-related injuries. In the US, falling on stairs is the second most common cause of accidental death after car accidents.
Hospitalizations were over $17 million in the 2013/14 fiscal year. According to the Public Health Agency of Canada, the societal and economic cost of stair-related accidents in Canada was $19.8 billion in 2004.
Several parties can be involved in slip-and-fall claims. Potentially responsible parties include:
- The Designer – Stairs should always be designed based on the building code of the relevant jurisdiction.
- The contractor – Responsible for following the design drawings to build the stairs.
- Owner – Responsible for maintaining the stairs to ensure they continually meet the requirements of the building code.
- Stair users – Stairs should always be used as intended.
In many cases, the party responsible for an accident is relatively easy to determine. If the stairs are perfectly designed but the contractor does not follow the drawings or install the handrails properly, the loss is the contractor’s responsibility. If the stairs are designed and built correctly, but the owner paints them in a manner that makes them invisible, the owner is held responsible.
The anatomy of stairs
Figure 1: A schematic of a flight of stairs.
The schematic in figure 1 shows all the crucial components of stairs. A step has a vertical and horizontal element. The vertical element is called the riser, and the vertical dimension is called the rise. The horizontal dimension is called a run. Sometimes there is a projection of the run beyond the adjacent step. There is tread depth, which is a combination of run and nosing.
The handrail may sometimes be located beside a wall. There should be a clear distance between the handrail and the wall. Otherwise, it will be impossible to grab the handrail when a person loses balance. The railing should be spaced close enough that people don’t fall out.
Different types of stairs
Figure 2: Different types of stair treads (reproduced from Appendix A of the 2012 Ontario Building Code.
The Canadian Building Code defines three classes of stairs: rectangular, angled, and Winders. For angled stairs, the treads are of different widths. Instead, they are trapezoidal to make a spiral shape. Winders have concentric tread edges, and some of the treads are triangular.
Building codes in Canada
The National Building Code of Canada (NBCC) is a model code without legal status. It was first published in 1941 and updated every five years, with the latest edition published in 2015.
Provinces and jurisdictions in Canada adopt or amend the NBCC, and then it becomes a legal document. Ontario has adopted and amended the NBCC to create the Ontario Building Code (OBC). The OBC was first published in 1975, with the latest edition published in 2012. This is now the legal document in Ontario. Every province has a building code that is based on the NBCC.
Design principles for stairs
In Canadian building codes, there are two classes of requirements for stairs. The first class is based on ergonomics, ensuring that an average healthy person can use stairs without difficulty. This means people with physical or cognitive disabilities and senior citizens who cannot use the stairs will require special assistance.
Examples of these ergonomic requirements are a reasonable range of rise and run of stairs. The stairs should not be so steep that you feel tired when you get up or so deep that you take a vast stride to walk up. Walking on the stairs should match your natural stride.
The second class of requirements is to ensure that the risk of falling is minimized. Examples of these requirements include non-slip treads, uniform run and rise to prevent tripping, and a reachable and graspable handrail by the sides of the stairs.
Example: Uniformity of stairs
Figure 3: A stair flight to a subway station in Sunset Park, New York.
People tripped over the stair flight at a subway station in New York. After an investigation, they found a half-inch difference between one of the steps and the adjacent steps at the top of the stair flight. Allegedly, there was one step at the top of the stair flight that people would trip over.
Figure 4: A section of stairs with a half-inch difference in rise.
A half-inch difference in a flight of stairs is imperceptible. However, this slight difference can create a safety hazard. When you take the first few steps in any stair flight, the brain automatically calculates the dimensions of the steps. Your brain then automatically adjusts your stride. If one step is odd, you’ll trip over it because it does not match the calculations. Therefore, uniformity is a crucial part of stair design.
OBC requirements for rectangular stairs
In residential buildings, the width of stairs should be ≥ 36’’. The width should be ≥34’’ in single-dwelling units. Nonresidential buildings must be ≥ 36’’ wide or 5/16’’ per person based on occupant load limits specified by the OBC.
Table 1: The OBC load limit specifications for different building types.
The maximum number of people to use a specific building can be calculated based on the limits specified in table 1.
Stairs should have enough headroom to ensure people don’t bump their heads into the ceiling. The OBC states that there should be a minimum of 77’’ headroom in single dwelling units and 81’’ in other buildings.
Figure 5: An illustration of staircase dimensions.
There should be a maximum of 12 feet between consecutive landings to avoid fatigue when people are using stairs.
3. Run and rise
There should be a minimum of three risers in dwelling units. In houses, fewer than three risers are a tripping hazard.
Table 2: Step dimensions, as outlined in OBC 2012.
The requirements for public buildings are generally stricter than for houses. People generally are not familiar with public buildings. The occupant is typically very familiar with the environment, including the stairs. Therefore, the requirements are stricter.
Figure 6: An illustration of OBC requirements for stairs with winders.
When there is a winder, it should be less than 90°, and the angle treads should be 30° to 45°. The run is measured at the center of the step, and the average run should be between 6’’ and 8’’.
4. Uniformity of stairs
Stairs should be uniform to avoid a tripping hazard. The slope of threads should be less than 1:50. The tolerance of rise and run between adjacent treads should be 3/16’’ (approx. 5 mm), and the difference between the largest and smallest run and rise should be 3/8’’ (approx. 10 mm).
Figure 7: A graphic representation of OBC requirements for rectangular stairs.
The difference between the tallest and the shortest riser should be 10 mm. The difference between the deepest and the shallowest tread should be 10 mm. Additionally, the nosing should only take away from the required tread depth by 15 mm.
Handrails guide the stair user. They also provide safety for people with impaired vision and those carrying bulky items. Using the handrail is the responsibility of the stair user. Therefore, if a slip-and-fall occurs while the person is not using handrails, that person is liable for the accident.
Table 3: The minimum number of handrails, based on stair location.
If the required width of the stairs is larger than 7’2’’, a third interior handrail is required.
Figure 8: An illustration of a third handrail.
The third handrail should be positioned such that the distance between any two handrails is not larger than 5’4’’. For safety reasons, someone in the middle of the stairs should have enough access to a handrail.
Figure 9: An illustration of dimension requirements for handrails.
The height of the handrail should be between 34’’ and 38’’. There should be an extension at the top and bottom of the handrail (min. 12’’) to indicate when the user reaches the top or bottom of the stairs. This is also crucial for visually impaired people, people with other disabilities, or those carrying bulky items. The distance between the handrail posts should be 4’’ (max).
Figure 10: A graphical representation of OBC requirements for rectangular stairs.
Rectangular stairs should have graspable handrails. There should also be a clear height for the stairs. A railing should be attached to the handrail, with a maximum opening of 4’’ for houses and 8’’ for industrial buildings.
Figure 11: A closeup of OBC requirements for handrail dimensions.
If there is a wall beside the handrail, there should be a clear distance between the handrail and the wall. Otherwise, users might hit the wall when they reach for a handrail, resulting in a slip-and-fall accident. Moreover, the handrail and its attachment should not reduce the stair width by more than 4’’.
Case study: Lack of handrail
A restaurant patron slipped and fell while walking down a stair flight.
Figure 12: The stair flight in question.
The building was renovated in 1980 when OBC 1975 was in effect. The measured stair width was 44.5’’. There was no requirement for uniformity of steps in OBC 1975. However, a handrail was installed only on the ascending side of the staircase, which contravenes OBC 1975.
According to OBC 1975, stairs wider than 44’’ require a minimum of two handrails. In this case, there was only one handrail, and the person slipped while coming down. That was a construction liability.
Figure 13: Illustration of the stair uniformity.
We measured the stairs, and the rise of every step is shown in figure 14. There was a ¼’’ difference between the adjacent steps. The maximum allowable tolerances under OBC 2012 is 3/16’’.
Figure 14: A closeup indicating the lack of stair uniformity.
The differences observed in these steps were not acceptable under OBC 2012. However, this was built and renovated before OBC 1975 was in effect. Therefore, the only viable contravention in this example was the lack of one handrail.
Attachment of handrails
Handrails must be properly attached to the wall or floor to ensure they are graspable. Attachments of handrails should resist a minimum 200 lbs concentrated load. In a public building, handrails should resist a minimum of 48 lb/ft distributed load.
Prescriptive construction requirements for dwelling units that can be replaced
- Handrails can be screwed to wood blocking or studs with a minimum of two wood screws penetrating (1.25’’) into solid wood.
- Attachments should be spaced 4’ maximum
- The first attachment should be 12’’ max. from the end of the handrail.
Figure 15: A graphical representation of handrail attachment requirements in single dwelling units.
The black dots in figure 15 represent attachments. These should be attached to the studs with a minimum of two screws or to a solid blocking with two wood screws. The solid blocking should be attached to the wall studs.
Case study: Attachment of handrails
Figure 16: The failed handrail attachment.
A resident grabbed the handrail in a dwelling unit to regain balance while walking upstairs. The handrail attachment failed, and the resident fell. When we attended the site, we noticed that the handrail was attached to drywall, not a blocking.
Figure 17: A photo (left) and sketch (right) of the improper handrail attachment.
We found solid wood in the wall cavity behind the drywall. The piece of wood is shown on the left-hand side image in figure 17.
We discovered that a framer installed the wall and stairs, and then the drywall installer did all the dry walls in the house. The handrail installer did not find any blocking between the studs. So, he cut a hole in the drywall, put blocking in the cavity, and attached it to the drywall using screws. Finally, he attached the handrail connection to that blocking and patched the drywall. However, this does not meet the requirements of blocking.
The OBC states that the blocking should be attached to wall studs. When you attach the blocking to the drywall, it carries the force on the handrail. But the drywall is too flimsy to carry that load, making this a contravention of the building code.
When the handrail installer found no blocking between the studs, he should have installed a proper blocking and then attached the connection. Alternatively, he should have attached the connection to the stud at the end of the wall. Another option would be to notify the contractor of the absent blocking. Then, the framers would install it.
There should be coordination between the sub-trades and the contractor because improvising can cause hazardous circumstances.
OBC requirements for spiral stairs
Figure 18: An illustration of OBC requirements for spiral stairs.
In spiral stairs, the run should be a minimum of 6’’ and an average of 8’’. Flight height should be 12’4’’ maximum between landings. The stair width should be 34’’ for dwelling units and 35.5’’ for public buildings.
1. Landing requirements
Figure 19: Landing requirements for rectangular (left) and spiral stairs (right). Source: OBC 2012 Part 9, Appendix A
For individual dwelling units, the landing for interior stairs should be 34’’. It should be 36’’ for exterior stairs. For public buildings, it must be 43’’.
Figure 20: Landing requirements for stairs with sharp turns. Source: OBC 2012 Part 9, Appendix A
Stair turns between 30°, and 90° require different dimensions. The exact dimensions for individual dwelling units and other buildings are outlined in figure 20. The imaginary line shown in the diagram is the Walking Line, which is 90’’ away from the stair end.
Landing requirements for spiral and angled stairs
Figure 21: Landing for stair turns over 90°.
When you have a ≥90° turn, the landing has a width of B, which carries along the turn.
Safety requirements for stairs
The following OBC requirements should be met:
- Strength of handrail attachments.
- The strength of stair framing and treads should meet the requirements of the OBC.
- The surface of stairs should be slip-resistant, wear-resistant, smooth, even, and free from defects. If the stair is wet, there should be a warning sign around the steps. If no warning sign is present and someone slips, the owner will be liable for the loss. In public buildings, treads and landings should have slip-resistant finish or slip-resistant strips that extend min. 1 mm above the surface. For houses, the following finishes are acceptable:
- Vertical grain softwood
- Resilient flooring
- Low-pile carpet
- Mat-finish ceramic tile
- Plywood (for stairs to unfinished basement or garage).
- There should be enough lighting for the stairs. If lighting is not maintained or repaired and someone falls as a result, the owner is held liable.
- The leading edge of the stairs should be designed appropriately. The top edges of the steps should be visible. Otherwise, the stair user cannot distinguish between the different steps, and they might trip. Sloped or beveled edges improve visibility. Furthermore, stairs in public buildings should have color contrast or a distinctive pattern to demarcate the leading edge of treads and landings.
Requirements for the leading edge of stairs
Figure 22: An illustration of a section of the staircase.
A step nosing should be 1.0’’ maximum. Close inspection of the nosing in figure 22 shows a straight line and a rounded part. However, the rounded part should not take away from the required tread depth by more than 5/8’’, whether it is nosing or a bevelled edge.
Table 4: Historical changes in OBC requirements.
Example: Fail on spiral stairs
Figure 23: The spiral staircase.
A person slipped and fell on a spiral staircase in a shopping mall. The building was constructed in 1997 when OBC 1990 was in effect. Three factors contributed to the accident. Surveillance camera footage revealed that the person was carrying bulky items, making that a user’s responsibility. However, the stairs were wet, and there was no warning sign installed around the wet stairs. That part was the owner’s responsibility.
Table 5: Uniformity of runs for the bottom flight of stairs (based on OBC 2012).
We also measured the run of the treads. The successive difference between the runs is shown in table 5. The difference between the shallowest and deepest tread was approximately 16 mm, and the allowable difference was 10 mm. However, OBC 1990 needs to give acceptable tolerance between runs. Therefore, the nonuniformity based on OBC 2012 was not litigable.
- Stairway accidents lead to numerous serious injuries and significant financial losses.
- Canadian Code key requirements address ergonomics and safety.
- OBC requirements for rectangular and spiral stairs vary considerably.