http://www.nrc-cnrc.gc.ca/ci-ic/article/v19n2-4
Codes Commission considers proposal to increase stair tread dimension in residences
Volume 19, Number 2
The tread dimension (i.e., run) of residential stairs is set to increase in the near future, if a proposed change in the fall 2014 public review is subsequently approved by the Canadian Commission on Building and Fire Codes (CCBFC). The proposed change was recommended by the CCBFC Standing Committees on Use and Egress and on Housing and Small Buildings, which found that increasing the stair run to 254 mm (10 in.) from the current minimum of 210 mm (8¼ in.) could reduce fall incidences by up to 64%. No change was proposed for the height of stair risers, as no correlation was found between falls incidence and lowering the rise dimension below the current maximum permitted rise of 200 mm (7.87 in.).
The Committees arrived at these recommendations by assessing the technical literature related to step dimensions as well as falls and injuries on stairs. Their aim was to determine if changing the rise/run step dimension would reduce the incidences of falls and injuries. They established that falls were three times more likely to happen during descent and that steps with a larger run dimension would provide better foot placement and greater stability margins, leading to fewer falls on stairs.
A cost/benefit analysis on various step dimensions was then carried out. Using 2012 as the reference year, the analysis compared the incremental cost of installing stairs with larger runs against the expected reduction in deaths and in health care costs. Five proposed run dimensions and two ceiling heights were used in this analysis.
The Committees determined that the optimum value from a cost benefit perspective occurred at a run dimension of 254 mm (10 in.) for both eight and nine foot ceilings. Subsequent calculations showed that implementing this change in the 2015 National Building Code could prevent 13,000 injuries and 39 deaths over a five-year period. The long-term benefits over 75 years would also outweigh the one-time incremental installation cost.
Based on this information, and the costs associated with introducing new stair dimensions, the Standing Committees recommended increasing the required run dimension of stairs to 254 mm (10 in.) within dwelling units, while leaving the required rise dimension untouched.
The recommendation was accepted by the CCBFC and a proposed change was developed for the fall 2014 public review. Following the public review, all comments will be examined. The final change, if approved by the CCBFC, will be published in the 2015 Codes.
