Carpenter Interprovincial Practice Exam Prep – Practice Tests & Study Guide

To determine the unit rise for concrete stairs with a total rise of 800 mm, one needs to first establish the number of risers that will be utilized in the design. Building codes and guidelines typically suggest a riser height that is comfortable for users, which often falls within the range of 150 mm to 200 mm per riser.

For a total rise of 800 mm, if you calculate using different typical riser heights, you find that adopting a height of 200 mm per riser results in exactly four risers (800 mm ÷ 200 mm = 4 risers). This setup is comfortable for most users and provides a balanced ascent as per construction norms, ensuring that stairs are not too steep, which is crucial for safety and usability.

Options that suggest a riser height less than 200 mm would lead to a higher number of risers, potentially making the stairs longer than necessary, while those greater than 200 mm result in too few risers, which might make the stairs uncomfortably steep. Therefore, a riser height of 200 mm is preferable to maintain a comfortable and safe gradient in a common residential or commercial stairway.