What is the maximum allowable height change for existing stairs?

The maximum allowable height change for existing stairs is crucial for maintaining safety and accessibility in buildings. The correct choice states that no more than a 1-inch variation can occur without the implementation of corrective measures. This guideline is in place to prevent tripping hazards and ensure a consistent stair rise, which is important for both safety and ease of use. When height changes exceed this limit, it may necessitate corrective measures like installing additional tread or altering the stair design to conform to safety standards.

The other options suggest greater allowances for height changes or conditions that aren't aligned with safety regulations. Allowing a height change of up to 2 inches, even if well-marked, could still pose a risk, especially for individuals with mobility issues. Similarly, variations tied to the presence of handrails or without the requirement for alterations do not adequately address the potential dangers of uneven stepping surfaces. Consistent height is critical for safe navigation on stairs, reinforcing why the strict limit of 1 inch is the standard.