Q: Our Home Inspector reported that our basement stair risers are inconsistent and could cause a tripping / fall hazard. What does that mean?
A: It is so easy to slip, trip or fall on a flight of stairs and having any inconsistent stair risers is a real safety hazard that was correctly identified by your Home Inspector. Other types of stairs deficiencies can include loose carpeting, worn / slippery treads, a missing handrail, as well as poor lighting. The National Building Code of Canada (NBCC Section 9.8) defines the consistency requirement for each riser (between adjacent steps) of less than 6mm (¼”). It also outlines how the height of each step or riser shall be between 125mm to 200mm (5” to 7-⅞”), as well as the depth of each tread or run shall be between 230mm to 355mm (9” to 14”). It is also important to note that stair risers that are too high or a tread run that is too narrow can also create a tripping / fall hazard.
One general rule of thumb my Dad taught us was to add twice the height of the riser, plus the length of the run and it should be close to 635mm (25”). As an example, if the step riser (height) is 7”; then the tread run (depth) should be about 11” (i.e. 7”+7”+ 11” = 25”). I’ve seen some contractors refer to this as the 7/11 rule. Ironically, this rule of thumb is somewhat similar to a causal walking stride and is still compliant with our existing building regulations.
I’ve actually seen this similar method used to create a set of stairs up a slight incline on a gentle backyard slope. The designer used a step riser of 100mm (4”) and a tread run that was close to 430mm (17”). In this particular case, we all found it very comfortable to use; as our bodies tend to naturally develop a steady rhythm (gait cycle) when we walk up or down an ergonomically designed flight of stairs. However, for that very reason, it is extremely important that we have consistency with each riser and tread run, as it is the inconsistency that can create a trip or fall hazard.
Surprisingly, any stair location that has only one or two steps can be particularly challenging. This is a design feature or flaw that is often associated with a sunken living room or family room, as these steps tend to be rather difficult to see or anticipate. For those types of stairs a visual or tactile clue should be considered, such as a change in flooring material or even a difference in color or maybe a contrasting color stripe on the nosing of each stair tread. Regardless, if you still have concerns, you should consult with a professional stair contractor on solutions to address your safety concerns.
Lawrence Englehart (Global Property Inspections) is a Registered Home Inspector and be reached at firstname.lastname@example.org or www.gpiweb.ca/englehart or www.facebook.com/GPI.HRM