Stairs cause a lot of household injuries, which is why the code is specific about them. The goal is consistency: every step the same height and depth so your foot lands where your body expects it.
Rise and run
For private residential stairs, the BC Building Code limits riser height (commonly up to about 200 mm) and sets a minimum tread run (around 255 mm), with tight tolerance between steps so no riser varies noticeably from the others. Uneven steps are a trip hazard and a common inspection failure.
Headroom and width
Stairs need minimum headroom so people don't hit their heads, and a minimum width for safe passage. These dimensions are set in the code and checked at inspection.
Handrails and guards
Stairs with more than a couple of risers need a graspable handrail at the required height (roughly 865 to 1070 mm above the tread nosings). Open sides of stairs and landings above a height threshold need a guard with balusters spaced so a small child can't pass through or get stuck.