What is the minimum stair width?

• A. 900 mm
• B. 800 mm
• C. 950 mm
• D. 1000 mm

Answer: (A)

The main idea tested is the minimum clear width a domestic staircase must have to allow safe and comfortable passage. In typical home construction, the required minimum clear width is 900 mm. This is the distance between finished surfaces of the walls along the stair, measured without counting any handrail projections. It ensures people can move up and down without crowding and provides space to grip the handrail. A narrower width, like 800 mm, would be considered too tight for a minimum standard. Wider options such as 950 mm or 1000 mm meet or exceed this minimum, but the question asks for the smallest acceptable width, which is 900 mm. For stairs that serve as an accessible route or in multi-occupancy situations, broader widths may be needed, but for a typical home, 900 mm is the baseline.