Slip resistance

Owners and managers of concrete surfaces are increasingly aware of the need to ensure safe floors and pavements. The preferred UK and European method for assessing slip potential is the pendulum test, based on the Transport Research laboratory (TRL) method and standardised in BS 7976 Pendulum testers.

Criteria for defining high, moderate and low slip potentials is given in CIRIA Report C652 (2006), Safer surfaces to walk on - reducing the risk of slipping drawn from research work, much of which comes from the UK’s Health and Safety Laboratory (HSL). The Health and Safety Executive (HSE) provide an assessment tool and recommendations for limiting values based on this research.

The generally accepted pendulum test value to achieve low slippage potential is 36 or greater. On a gradient, this value is increased e.g. minimum of 41 for a 1:20 incline. Many low porosity materials such as granite and power trowelled concrete meet these requirements in dry conditions but not when the surface is wet. The type of potential contaminates on the surface, whether dry (paper, plastic) or wet (water, oil) must be considered in any assessment of hazard. Other influences include the environment, footwear and user behavior.

Surface roughness can also influence slip resistance, the shape and spacing of the peaks being important. The HSL intend to carry out further research into the inter-relationship between other surface parameters. The surface roughness value (Rz) in microns, should be used as a guide and not a sole indicator of slip potential.

In layman terms it must be noted that smooth concrete floors, whether densified by trowelled or honed for a polished appearance, have a similar resistance when dry. However once wet or dusty, a smooth finish can be more than twice as slippery as say a rough float, tamped, brush or other textured finish.