Many of us have 'stumbled' up or down when the step was too short or too tall. Same with a difference in riser height in a single stairway. The average person has to modify their usual stride length to use stairs like that. Take stairs with tread areas of two feet or more. Most of us have experienced that when we have stumbled or felt uncomfortable on stairways(interior or exterior) with treads/risers that are unusual.

I was taught stair codes were developed because humans have an inbred muscle memory height for repetitious stairs. Therefore, local building codes in those areas reflected the necessary changes from the International codes(which are adopted by many governments). I discovered (had never been east of the Big Muddy) houses in mountainous/hilly areas were built tall and skinny by necessity. I never measured them, but in hindsight, there was no way those stairs would pass code now. I almost felt like I was climbing a ladder. When I was stationed in Aberdeen, Maryland, I visited a house that had the steepest, most narrow stairs I had ever seen. So how do your stairs work out according to the article?ħ.357 (r) + 9.077 (R) = 16.434 (below the minimum suggested)ġ4.714 (2r) + 9.077 (R) = 23.791 (again below the minimum suggested)ħ.923 (r) + 9.833 (R) = 17.756 (above the minimum suggested)ġ5.846 (2r) + 9.833 (R) = 25.679 (So here's your answer although I still say it will be difficult for the elderly, vertically challenged and young children to navigate.)

Twice the rise plus the run (2r+R) should be within an inch of 25”. The rise plus the run (r+R) should be within an inch of 18”. I also agree that any less would feel awkward. I think Mark B would agree it was fine when he visited my house and he's a taller dude.

Mine are a 7' riser with a 10' tread (run). You can cheat a bit up or down, but below 17” and more than 19” will result in steps that require strides either too big or too small for most people.' Why? That’s what most people find to be a comfortable stride on most stairs. 'Rule one says that rise plus run (r+R) should equal 18 inches. It’s the horizontal distance from the face of one riser to the face of the next riser, or from nosing to nosing, and the other stringer cut-it’s NOT the size of the tread itself, which includes a leading edge overhang of ¾” to 1 ¼” (according to the IRC for most residential stairs).' 'The “Run,” however, seems to cause some confusion. As the article states, you don't consider the nosing as part of the tread width.

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