What are the standard treads and risers for a regular stairs in a house?
Friday, January 17, 2020
A common combination is 11-inch treads and 7-inch risers, but there is no single standard and the two numbers are often adjusted based on the space available. The International Residential Code sets the maximum riser (vertical part) of a stair at 7-3/4” and the minimum tread (horizontal part) at 10”. Put them together, and you have the steepest stair allowed. However, when a tread is less than 11” it must have a nosing (extension past the face of the riser below) long enough so that the combined length of tread and nosing equals 11”. So a 10” tread would require a 1” nosing. See our blog post When is a nosing required on a stair tread? for more on this.
But the ratio of the riser height to tread depth is the most important thing to get right. If you have ever walked down a garden path with stepping stones that were either too close or too far apart, then you are familiar with the kind of awkwardness that a stair with the wrong riser to tread ratio creates in the cadence of the person ascending or descending them. The only difference is that a stair with a bad ratio can be dangerous.
The building code does not specify a ratio, but one standard that is often used is that one tread plus two risers should equal 24 to 26 (T + 2R = 24 to 26). So, as the tread lengthens, the riser must get shorter to make a comfortable stepping pattern—and vice-versa. When that formula is applied to 11-inch treads and 7-inch riser, the total is 25.
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