Steps between a driveway and an entry with inconsistent riser heights are:

Stair climbing is largely automatic — after the first step or two, the body predicts the rise and places the foot without conscious measurement. That prediction is what makes uniform risers a safety requirement rather than a construction nicety. An irregular riser breaks the prediction at exactly the moment the walker's weight is committed and their eyes are elsewhere, which is why non-uniform risers are among the most consistently cited causes of stair falls. Exterior steps make it worse: they are often built up over time as grade settles or a driveway is resurfaced, they are used while carrying things, and they are wet, icy or dark far more often than interior stairs. The inspector reports the irregularity as a fall hazard and notes the location, without needing to measure against a specific tolerance to justify it.

Users predict the next rise from the previous one, so an inconsistent riser disrupts the stride at the moment weight is committed. That is a fall hazard, and it is why uniformity is required rather than merely preferred.

Stairways are expected to have uniform riser heights and tread depths within a small tolerance across a flight, because users climb by prediction rather than observation. Inspectors report irregularities as safety items along with handrails, guards and lighting.

The Foot Expects the Last Riser. Change it and the walker finds out mid-step, with their weight already moving.

You do not need a code tolerance to report it. Describing the measured variation and the hazard is sufficient and is what the client can act on.

• •Treating riser uniformity as an aesthetic preference
• •Reporting a suspected footing cause instead of the hazard
• •Exempting exterior steps from uniformity expectations