For stepped assembly aisles with a slope exceeding 12.5 percent, the minimum tread depth shall be _____ inches.

• A. 8.5
• B. 10
• C. 11
• D. 12

Answer: (C)

In the context of stepped assembly aisles, which are common in venues such as theaters and auditoriums, the Building Code specifies that when the slope exceeds 12.5 percent, there are certain requirements for tread depth to ensure safety and accessibility.

The minimum tread depth of 11 inches for slopes greater than 12.5 percent is designed to enhance stability and reduce the risk of falls. A deeper tread provides greater space for foot placement, which is especially important in areas where the incline may make it difficult to maintain balance. This requirement is grounded in safety principles aimed at accommodating the movement of individuals in environments where they may be navigating steep steps.

The other choices do not meet this guideline set forth by the code, as they propose shallower tread depths. Shallower treads might not provide the necessary support and stability when negotiating a steeper slope, thus not fulfilling the key safety objectives outlined in the Building Code.