What is the minimum step depth (tread) allowed on a stair?
Saturday, February 29, 2020
The depth of a stair tread should not be less than 10 inches, measured vertically between the leading edges of adjacent treads, according to the International Residential Code (IRC 3220.127.116.11). The maximum allowable varitation in tread depth is 3/8 inch.
But a nosing (extension of the tread leading edge past face of riser below it) is required for stair treads less than 11 inches in depth to create a minimum tread surface of at least 11 inches (IRC 318.104.22.168). A nosing cannot project less the 3/4 inch or more than 1-1/4 inch.
Also, see our blog post What is the steepest residential stair allowed?
Here’s links to a collection of our other blog posts about STAIRS:
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