I'm designing a stairs in a very tight space that has an upper landing and a lower landing, each segment requires a 90 deg turn. If the landing riser heights are different from the main run - does this present a hazard? If so - why?

Presently the upper landing is 10.5" drop, followed by steps of ~9.5", and back to 10.5" on the lower. The stair runs are 11.5"

  • 1
    My thought is - once the walking gait pattern in broken - you effectively have a different stairs. For example, the stairs in my home go to a small landing at the front door - then there is a step out of the front door that drastically different height. 10.5 is a large drop (although the step stool I use is 14") - but you fall into the landing - not the stairs. I'm aware of the code - but by code a stairs are not possible - so I've been using a ladder. Code is also based on average size of people - how well would code stairs work for small or large people?
    – pathfinder
    Commented Apr 20, 2018 at 13:54
  • What do you mean by the "landing risers"? Are you referring to entire stair runs between landings, or the single rise above or below a landing?
    – isherwood
    Commented Apr 20, 2018 at 13:56
  • @isherwood The first step down would be 10.5", followed by a 90 deg turn, followed by steps ~9.5", followed by a 90 deg turn, followed by what I call 2 steps to the floor. Maybe riser isn't the correct word - so I call them drops.
    – pathfinder
    Commented Apr 20, 2018 at 14:01
  • I think the answer has been given - diy.stackexchange.com/questions/38128/…
    – pathfinder
    Commented Apr 20, 2018 at 14:06
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    If that's a duplicate, please delete your question.
    – isherwood
    Commented Apr 20, 2018 at 14:12

1 Answer 1


Code says risers can’t be more than 8” high and can’t vary from the largest to smallest by more than 3/8”. (See IRC R311.7.5.)

Treads can’t be less than 9” and can’t vary by more than 3/8”.

  • The question was does it present a hazard - not what does code say.
    – pathfinder
    Commented Apr 20, 2018 at 13:47
  • There are “exceptions”: If it’s just access to mechanical space, spiral stairs, etc.
    – Lee Sam
    Commented Apr 20, 2018 at 13:52

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