What is the maximum unit rise for a stair, according to the National Building Code?

The maximum unit rise for a stair according to the National Building Code is set at 150 mm. This standard is established to ensure safety and accessibility in stair design. A rise of 150 mm is comfortable for users, making it easier to ascend and descend stairs without excessive strain.

When steps exceed this maximum rise, they can become dangerous, increasing the risk of trips and falls, particularly for individuals with mobility issues. Maintaining this rise helps provide a uniform and predictable stepping height, which is crucial for creating safe and user-friendly structures.

Lower maximum rises would potentially compromise accessibility and can't accommodate various construction scenarios where 150 mm allows for a balance between usability and design flexibility. Higher rises, as seen in the other options, may lead to discomfort or hazards, which is why they are not permissible under the code.