Why is surface roughness important?
To have a low slip potential a floor needs to have enough microroughness to break through a contaminant and make solid-to-solid contact with the pedestrian's heel.
The thicker the contaminant, the rougher the floor needs to be to have a low slip potential.
HSE guidance and tools only refer to Rz data. Rz is a measure of total surface roughness, calculated as the mean of several peak-to-valley measurements. However a range of other roughness parameters can be measured with surface roughness meters.