Stair Runs and Risers


Why does your Stair Case Calculator always give one less run than the number of risers?


A carpenter usually never builds his first step even with the top floor, he drops the first step down one riser. This riser is the one that puts the number of runs one less than the risers, but it still has to be in the calculation of the total rise.

The only time I ever build the top step level with the floor is when I build a set of stairs outside of a patio door, when an older couple may trip over the sill on their way down to the first step. In this case the number of risers equals the runs.


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