Surface Roughness Testing (Rz) in Bristol & the South West

Surface roughness measurement (Rz) records the micro-texture of a floor surface using a stylus-type roughness meter. It is a useful complement to pendulum testing — particularly in forensic work, where understanding both dynamic friction and surface texture builds a fuller picture of slip risk.

How Rz Testing Works

A precision diamond stylus is drawn across the surface over a defined sampling length. The instrument records the vertical variations and reports them as Rz — the average peak-to-valley height in microns (μm).

This measurement captures texture at a scale that pendulum testing cannot fully describe, and is especially relevant when contamination (water, oil, food residue) reduces the contribution of larger-scale roughness.

Rz and Slip Risk

HSE guidance correlates Rz to slip potential when the floor is wetted with water:

Below 10 μm: High slip potential
10 to 20 μm: Moderate slip potential
20 μm and above: Low slip potential

Different contaminants change the picture. Heavily polished floors with low Rz can be acceptable when dry but become hazardous as soon as fluid is introduced.

When to Specify Rz Testing

Forensic investigation following a slip claim
Cross-checking pendulum results, especially in borderline cases
Long-term monitoring of floor wear and polishing
Verifying that anti-slip treatments have produced the texture they were designed to

Surface Roughness Testing (Rz) in Bristol & the South West

How Rz Testing Works

Rz and Slip Risk

When to Specify Rz Testing

Need surface roughness testing in the South West?