Replies

1. 
   JohnWW | Jun 11, 2007 09:23pm | #1

   Stair layout is pretty straight forward, the details of building a stair can be daunting depending on the type of construction.

   For the layout, a good stair rise is around 7 to 7 1/2 inches per step, so take the distance between the the two finished floor surfaces and divide by 7.5, in your case that would be 109/7.5=14.53.  Being you came up with a fraction, you'll have to use either 14 or 15 risers.  I would use 15 risers which would make the rise per step 7.27 inches.  Using only 14 risers would make the steps taller than recommended.

   The rule of thumb for stair layout is that the rise and run for one step should add up to 17 to 18 inches.  If we take the middle ground, 17.5 inches, for the calculation the run would be 17.5 - 7.27=10.23 inches. 

   In any stair there is always one less tread than there are risers, so you are going to need 15 risers and 14 treads.  14 treads at 10.23 inches each means you will need a total run of 14x10.23=143.22 inches.  You were planning on a 120 inch run, so you have a problem.

   I would strongly recommend that you don't try to wedge the stair into the available space by making it steeper, it will be awkward and dangerous to walk on, especially for kids and the elderly, and a steep stair will violate building codes.  Possible solutions are to find more space for the stair or to add landings or winding steps.

   You will probably have more questions after mulling over the math, so feel free to ask.

   John White 

   
   

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   Edited 6/12/2007 10:42 am ET by JohnWW

1. 
   chewey | Jun 12, 2007 07:18pm | #2

   Hi John:

   Understanding the math is important but perhaps some of the details were not clear in my original message.  Because I'm not having risers and the stairs will essentially be "open", the run(tread) of approximately 10 inches will protrude under the next step, above.  Does this not change the equation?  thanks chewey

1. 
   JohnWW | Jun 12, 2007 07:41pm | #3

   Sorry to say it doesn't change the math, when you are climbing up the stairs the ability to stick your toes under the step above doesn't count because you can't lift your foot upward, it would snag on the upper step, you need the clear 10 inches+ from the nose of one step to the nose of the next step.

   John W.

   Edited 6/12/2007 1:38 pm ET by JohnWW