NCIDQ Interior Design Professional Exam (IDPX) Practice Exam

What is the minimum dimension for the bottom stair handrail extension?

1. A. 12"

2. B. Not less than the depth of one tread beyond the bottom riser

3. C. 18" from the bottom of the tread

4. D. Cannot be less than 30"

The correct answer is: B. Not less than the depth of one tread beyond the bottom riser

The minimum dimension for the bottom stair handrail extension is not merely an arbitrary measurement; it is defined to ensure safety and functionality. Extending the handrail at the bottom of the stair beyond the last riser, specifically by the depth of one tread, provides a clear and accessible support for individuals using the stairs. This extension allows a person to grasp the rail before they reach the stairs and to maintain that grip as they descend, thus reducing the risk of falls. Building codes, including those promoted by the International Building Code (IBC) and the American Society of Civil Engineers (ASCE), emphasize that for handrails to effectively assist users, they need to extend adequately in a way that accommodates the typical movement of people as they approach and leave the staircase. The depth of the tread is an appropriate and standard measurement to use since it reflects an average distance that would be encountered in practice. Other options, while they might represent some measurements relevant to handrail design, do not establish the same level of practical usability or safety as the correct choice does. Therefore, this specific extension is critical for proper handrail installation and compliance with safety guidelines in stair design.