R311.7.5.2

Section R311.7.5.2 is titled 'Treads' and covers the requirements for the horizontal component of steps in a stairway. A minimum depth, method of making depth measurement, and depth consistency within a flight are established. The purpose of this section is to reduce trip and fall hazards.

The model shows two partial stairways. The left stairway shows the vertical planes extended from the foremost projection of the treads, which are used to measure the depth of the treads, and the minimum tread depth. The right stairway, shows two actual tread depth measurements, with the larger tread depth being greater than 3/8" of the smaller tread depth. The red X denotes that this stairway is not compliant with this section of the code. An inspector needs to measure every tread, in every flight, to assure that in each flight the largest tread depth doesn't exceed the smallest by more than 3/8".