Finding the Staircase Footprint :: Architectural Turnings

Finding the Staircase Footprint	Last Updated: Thursday, December 31 2009
By Kim Vedros - Friday, December 11 2009	Comment(s): 0 \| Overall Rating:

I got a call some time back from friend regarding his stairway construction. His new home was "blacked-in" and his carpenters were ready to frame in the stairway. There appeared to be a discrepancy, however, between the house plans and the reality of his foyer space. The plans showed the stairway neatly fitting in the foyer and ending where the great room began. It was apparent, however, that the architect had not left enough room between the front wall of the home and the first step. And so, my friend called me to see what his options were. This scenario is played out more often than you might think. So I thought I might write a few simple steps to calculate the "footprint" of a stairway.

The first step in establishing the foot print of the stairway is to measure the height of the staircase from finished floor to finished floor. If your floors are not finished you will have to add the floor thickness(es) of the proposed floor(s) to your rough measurement.
Divide the height by 7 1/2" (for example:132 / 7.5 =17.60) What this number tells us is that there will be 17 risers (and a fraction) To find the actual riser height divide 132 by 17 (132 / 17 = 7.76") - 7 .76 is your actual riser height.
Since you have 17 risers you know that there will always be one less tread than risers. And so there are sixteen treads to this staircase.
Multiply 16 X 10.5 and this will get the length of your stairway. 16 X 10 = 160" Your staircase with this size tread will be 160" long
Next step is to determine if 160" will fit into the available space. If so - great!! If not you may have to reduce the number of steps (which will yield a higher riser). The rule of thumb that I like in considering what will work is 2 risers plus one tread should equal 25" for the ideal riser and tread dimensions. What this little formula means is that as the riser increases in height the tread will decrease in depth. Apart from the formula though there are stair codes in most communities that will dictate riser height and tread depth. So ultimately, consult your local building code.

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