What type of calculation is performed for stair tread depth according to building codes?

The depth of stair treads is fundamentally connected to the height of the risers, as building codes dictate specific design parameters to promote safety and usability. This relationship is established in design guidelines, typically referred to as the "tread and riser formula," which helps ensure that the stairs are not only comfortable to ascend and descend but also comply with safety regulations. Specifically, the recommended tread depth often corresponds to the height of the risers in a way that balances the two measurements for optimal user experience.

In this context, a calculation that links the tread depth directly to the riser height provides a clear methodology for designing stairs that effectively minimize the risk of trips and falls, adhering to codes that prioritize safe construction practices. Thus, the choice reflecting this formula aligns well with the requirements laid out in the building codes, establishing it as the sound approach for determining stair tread dimensions.

The remaining options do not pertain to the specific calculations related to tread depth and riser height. Measurements of stair width, averages of components, or calculations concerned with aesthetics such as color and finish do not fulfill the specific technical needs dictated by safety regulations in stair design.