Proposed Change 1772

Sentence 3.4.6.5.(3) of Division B of the NBC provides requirements for intermediate handrails where stairs or ramps are too wide to readily reach one of the handrails on the outer edges of the stair or ramp.

Clause 3.4.6.5.(3)(b) is worded such that for stairs or ramps that require an intermediate handrail, one portion of the stair or ramp must have the minimum width required. As it is written, this provision could be interpreted to mean that the dimension (1 100 mm in many cases) must be the exact minimum width. The 1 100 mm width allows for two people to use the stairs or ramp side by side. Clause 3.4.6.5.(3)(c) indicates that other portions of stairs or ramps must have a clear width of at least 510 mm between handrails, leaving room for wider portions of stair or ramp, if desired. These portions are intended to be wide enough to allow at least one person to use the stairs. The intent for both requirements is to provide minimum dimensions to serve in emergency situations where people are likely to circulate only in one direction.

It is intended that the portion of stair or ramp having the minimum width required also be “at least” this wide, while also having handrails within reach as required by Clause 3.4.6.5.(3)(a). However, the Code language does not currently reflect this intent.

Additionally, there is confusion where the Code uses different terms such as “minimum width” and “clear width”, especially in the same Sentence. Some Code users may interpret these terms as having the same meaning, while others do not. This could lead to different levels of performance in exit facility design, which may not be sufficient to facilitate a timely evacuation as originally intended by the Code. For clarity and ease of design and enforcement, this proposed change clarifies the terms used in this Sentence by introducing an explanatory Note and related figures.

The dimensions of portions of stairs or ramps were previously reviewed and given due consideration. It is acknowledged that some stair or ramp widths might not comply with the existing requirements (for example, for stairs that are 1 400 mm wide, a portion of 1 100 mm plus a minimum of 510 mm for the other portion is not possible). However, this would be the case regardless of the minimum dimension (510 mm or another number).

This proposed change revises Clause 3.4.6.5.(3)(b) to reflect the Code intent to require a portion of stairs or a ramp to be “at least” the minimum width required and clarify how the width should be measured.

This proposed change also introduces explanatory Note A-3.4.6.5.(3) to clarify where the intermediate handrail is required by Sentence 3.4.6.5.(3) and how to measure the relevant dimensions. Additionally, two figures are provided to illustrate where an intermediate handrail is not required and where a handrail is required.

The proposed change clarifies the existing provisions to avoid misinterpretation and for consistent application by designers, builders and building officials.

As the proposed change clarifies the existing provisions, no increased cost is associated with it. Unnecessary costs associated with redesign or rework can be minimized by clarifying the current Code provisions. The clarification would provide guidance for designers and building officials so that the design of stairs and ramps can permit the efficient evacuation of people, as well as consider normal daily traffic on the stairs and ramps.

Depending on how the Clause 3.4.6.5.3.(b) was previously interpreted, the addition of “at least” would not have a particular impact. However, where it was interpreted to mean that a portion of stairs or ramps was required to match the exact exit width (for example, exactly 1 100 mm), the proposed change would provide additional flexibility in stair or ramp design, while still maintaining the level of safety (handrails within reach from any location in that portion of stair or ramp).

The proposed change makes consistent use of the term “minimum width”, which would allow ease of design and enforcement in the field. The width at shoulder height of the average person is considered to be the more critical measure for egress purposes than “clear width” between handrails.

The clarification provided in the proposed change should facilitate the more consistent application of the requirements. Stair and ramp widths can be measured using existing methods and basic measurement tools.

The proposed change clarifies the existing provisions for building designers and authorities having jurisdiction so that the provisions can be interpreted consistently.