Question

How would you use the following formula?

2R + T = 25

Answer

This is the standard formula for determine the relationship between Risers (R) and Treads (T) in the design of stairs. The typical code minimums for non-residential stairs with 7-inch risers and 11-inch treads fall within this relationship. The formula is valuable for determining the tread width when using either a taller or shorter riser. A 6-inch riser would have a 13-inch tread, while an 8-inch riser would have a 9-inch tread. The formula is designed to take into account the length of a person's stride and how it changes depending on the steepness of the stair.