So I'm trying to design a stair railing and I have to have the spaces between the bars to be 4". I just can't think of the way to do the math that would tell me how wide the bars would have to be.

My bars are more like panels.

Railing length: 15' 7 3/16" Design wants: I want one of the ends of the railing to end with a bar/panel. I would like the panels to have a min width of 2".

discussion architecture

  • 1
    The typical requirement is "less than 4" or "does not allow passage of a 4" ball" (infant head simulation) rather than precisely 4" – Ecnerwal Mar 19 '17 at 2:23
  • Ok, I was just wanted that because I want the most for light to bable to pass through – RetroCUBE Mar 19 '17 at 2:30
  • Is the specified length the actual rail length (diagonal) or the horizontal distance the railing covers? – bib Mar 19 '17 at 2:34

Reduce it to inches. 15 feet is 180 inches, plus 7 & 3/16 inches

Total distance 187.1875 inches. Divide by 6 (4" space and 2" slat) 31.1979166666667

Per my understanding of stair code (LESS than 4", not 4") use 32 2" slats. Or 3" or 4" slats, for that matter.

Alternatively, divide by 32 (proposed number of slats) and get a unit (slat and space) of 5.849609375 ; or divide by 31 and get a unit of 6.0383064516129

  • What did you mean when you said "Reduce it to inches. 15 feet is 180 inches, plus 7 & 3/16 inches" ? – RetroCUBE Mar 19 '17 at 2:35
  • The math is more straightforward if you have it all in inches, rather than feet and inches. 12 inches to a foot, so 180 inches in 15 feet; then you had an additional 7-3/16. – Ecnerwal Mar 19 '17 at 2:37
  • So then I just divide the length of the railing by what? – RetroCUBE Mar 19 '17 at 2:40
  • Slow down and read, I told you this 3 different ways in the answer as written. – Ecnerwal Mar 19 '17 at 2:44
  • The Big Bang Theory would be proud. Btw, yes, by code it's, "so that a 4" sphere cannot pass." – Lee Sam Mar 19 '17 at 2:45

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