Slip resistance
Pendulum test value (PTV) to coefficient of friction and slip potential
- where
- equivalent dynamic coefficient of friction
- pendulum test value
- PTV above the low-slip threshold of 36
Explain this equation
Classifies a floor tile by its pendulum test value and gives the matching coefficient of friction. Use it when choosing tiles for bathrooms, kitchens, entrances and outdoor areas.
PTV is the reading from the pendulum tester, which swings a rubber-shod foot across the surface, usually wet. μ is the equivalent friction coefficient between foot and floor. The margin shows how far above or below the HSE low-slip line of 36 the tile sits.
The conversion reflects how the pendulum’s spring-loaded slider behaves: PTV is roughly μ times 100 at low values, with a small correction built into the 330 term. HSE treats 36 and above as low slip potential, 25–35 as moderate and 24 or less as high.
Sense check: PTV 36 gives μ about 0.37; PTV 24 gives about 0.24. A polished porcelain may read 10–20 wet, a textured external tile 45 or more.
Watch out: use the wet result for any area that can get wet. Ramp R-ratings come from a different test and cannot be converted reliably to PTV.
Classifies a floor by its pendulum test value using the HSE/UKSRG bands and converts the PTV to the equivalent dynamic coefficient of friction.
Enter your values to see the result.
Good to know
HSE bands: PTV 0–24 high, 25–35 moderate, 36+ low slip potential. Use the wet result for any area that can get wet (bathrooms, kitchens, entrances, outdoors). Surface roughness Rz gives a quick screening check: below 10 µm high, 10–20 µm moderate, 20 µm and above low slip potential in water-wet conditions. Ramp (R9–R13) ratings from DIN 51130 are a different test and cannot be converted reliably to PTV.
Common mistake
Quoting a dry PTV or a ramp R-rating for a wet room. Almost every floor passes dry; the wet result is the one that matters.
Limits
The μ conversion is the relationship used to tabulate the UKSRG bands; it relates to the pendulum only. Real slip risk also depends on contamination, cleaning, footwear and use. The pendulum test is to BS 7976-2.
Sources
- HSE GEIS2: Assessing the slip resistance of flooring (PTV 0–24 high, 25–35 moderate, 36+ low slip potential)
- Hunter et al. (2015) Understanding the friction measured by standardised test methodologies (Table 1: PTV 36 ≈ CoF 0.367, PTV 24 ≈ 0.235)
- BS 7976-2:2002+A1:2013 Pendulum testers – Method of operation
Results are calculations from the published methods and manufacturer figures shown, and depend on the data you enter. Always follow the tile, adhesive and grout manufacturers’ instructions, BS 5385 and the Tile Association guidance. Coverage rates vary by product and substrate. Check prices and VAT rules with your own records and HMRC.