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I am designing a staircase to be built inside a house. At the moment I am not concerned about materials or supporting structure but rather with the usability and safety. I realize I may not build a perfect staircase which is compliant with the code due to space constraints.

I have read a few articles about the requirements for safe stairs, such as angle, raiser height, tread depth, overhang length and walk line.

Based on what I have read and the set of constraints imposed by the location where the staircase has to fit, I came up with a design. I do see a few limitations of this design. Specifically, I am concerned about the following:

  • Some stairs have width at walk line of just ~17cm(6.6"). I've read the minimum required is ~25cm(10"). Is this going to be much of an issue?
  • I am not sure if I have measured the distance to the walk line correctly (please see the screenshot). Please correct me if this is wrong.
  • Some stairs are 10cm(~4") wide at the narrow end. Is this acceptable?
  • Rise is 19cm(~7.5"). Is this acceptable?

stair size overview multiple stair sizes walk line

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    make steps 6 through 12 all the same angle ... 180 degrees divided by 7 – jsotola Aug 18 at 4:41
  • @jsotola thanks, in fact step #9 has some width to spare so may allow me to make other steps wider. – Andrew Aug 18 at 4:50
  • make sure that the resulting steps are not too wide ... you may have to adjust the angle of more steps – jsotola Aug 18 at 4:58
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In the U.S., (I see you use cm. Metric is too difficult for us Americans,) there are several types of stairs that “bend” around corners, etc. We call them 1) spiral stairs, 2) winding stairs (your stair design), 3) curved stairs.

One of the most important requirement in the Code is that the stairs must be uniform. That means uniform height, depth, depth at wall line, etc. (I see your treads vary in width 31 cm from the narrow end.)

For spiral and winding stairs, our Code requires a minimum of 7 1/2” wide at a point 12” from the narrow end (the walk line).

Nosings shall not exceed 1 1/4” beyond the riser below and beveling nosings shall not exceed 9/16”.

Standard risers shall be a maximum of 7” and a minimum depth of 11”. However, in residences, the maximum riser height shall be 7 3/4” and the minimum tread depth of winder stairs is 10” in residences. (There are exceptions to these dimensions for spiral stairs...see above.)

Remember, using winding stairs is most dangerous descending. The likelihood of missing a narrow tread while descending is far more likely than missing a tread ascending. Make sure handrails are installed on both sides of the stairs...if not possible, make sure you have a handrail on the right side descending.

BTW, excellent drawing.

  • I have updated the drawing with inch sizes. By saying that the Code requires stairs to be uniform, do you mean the depth at walk line should always be uniform? For example, if the stairs that go straight have width at the walk line of 11" should the "bent" stairs also be 11" wide at the walk line? – Andrew Aug 18 at 5:44
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Honestly, I'd suggest a spiral staircase instead. Those are specifically designed for fitting a staircase in a confined space, and should provide a better experience than a custom job.

  • This makes sense. However, I'd like to close the space below the staircase and use it for storage. This may be somewhat more difficult for a spiral staircase. Also, my understanding is that a spiral staircase would have narrower stairs and thus would be less user-friendly. Wouldn't it? Would it be better to have all stairs slightly narrower but uniform (spiral) instead of the custom design? – Andrew Aug 18 at 5:48
  • @Andrew "uniform" is always helpful in a user interface - whether navigating a computer screen or navigating stairs. – manassehkatz Aug 18 at 6:52
  • More storage is always good, but I think your first priority should be a staircase that is safe and functional, and that's going to be an issue in your case due to the restricted area. And, yes, I would prefer a uniform experience. A staircase is as bad as it's worst step, and there's a bunch of bad steps in your design. – user3757614 Aug 18 at 6:59
  • Side note: I'm assuming you're remodeling a rather old house, and that's the reason you're having to cram this staircase into about half the space it needs, but if you're building a new house, or can steal a bit of space from somewhere else, do so. – user3757614 Aug 18 at 7:02
  • Also, if you want storage under a spiral staircase, it's certainly possible, you just can't use a prefab one. The open structure of spiral staircases isn't a requirement. – user3757614 Aug 18 at 7:07

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