Why outdoor stairs carry a disproportionate frost risk
Stair treads have a high surface area-to-mass ratio. They lose heat from the top face, the riser face, and through the structure below. They are frequently shaded from solar gain by the building above them. And in manual de-icing operations, steps are often the last surface to receive treatment - because they are enclosed, awkward to access with gritting equipment, and quickly stripped of salt by foot traffic.
The result: stair treads ice earlier, more severely, and for longer than adjacent flat surfaces in the same conditions. In UK winters, this commonly means an iced entrance staircase at 08:00 when the surrounding driveway is still clear - and when the gritting team has not yet identified a problem.
Falls on steps are more severe than falls on flat surfaces. The step geometry creates a height differential - a person falling on stairs falls further and impacts at a different angle than on flat ground. HSE slip, trip, and fall data for commercial premises consistently reflects this: staircase incidents are disproportionate to the number of steps in service. The legal context under the Occupiers' Liability Act 1984 is clear: a foreseeable hazard that causes injury is a liability failure.
