Floor Slip Resistance: The Pendulum Test, PTV Values and BS 7976

Quick Answer: The recognised UK method for measuring floor slip resistance is the pendulum test to BS 7976, which produces a Pendulum Test Value (PTV). A PTV of 36 or above is a low slip risk, 25–35 is a moderate (significant) slip risk, and 24 or below is a high slip risk. The HSE and the UK Slip Resistance Group (UKSRG) treat the pendulum as the primary in-situ method; DIN ramp R-ratings are a manufacturer's lab figure and are not a substitute for a PTV in real conditions, especially when the floor will be wet.

Summary

Slips and trips are the single biggest cause of major injuries in UK workplaces, and a wet floor that was fine when dry is the classic culprit. As a flooring contractor, tiler, resin layer or builder, you are often the one specifying or laying the surface that determines whether someone goes over. Knowing how slip resistance is actually measured — and what number to aim for — turns "it looks grippy" into something you can quote, specify and defend.

Slip resistance matters because the law expects floors to be suitable for their use, and a slip injury can become an enforcement matter or a civil claim. The pendulum test is the method the HSE and the courts recognise. It mimics the action of a heel striking the floor and measures the dynamic friction, giving a Pendulum Test Value (PTV). Crucially it can be done on the floor in place, in the dry and the wet, so it tells you how the floor performs in the conditions that actually cause slips.

The most damaging misconception on site is that a DIN 51130 "R-rating" (R9 to R13) proves a floor is safe. R-ratings come from a laboratory ramp test with a person walking in boots on an oiled surface — useful for comparing products, but not a measurement of the floor as laid, not specific to your contaminant, and not the UK in-situ benchmark. A floor can carry a good R-rating and still produce a high-slip-risk PTV once it is laid, dirty and wet. When slip safety is a real concern (entrances, wet rooms, kitchens, ramps, pools), specify and verify by PTV.

Key Facts

Quick Reference Table

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PTV (pendulum) Slip potential Practical meaning
0–24 High Unsafe for wet pedestrian use; remedy required
25–35 Moderate / significant Borderline; manage or improve
36–44 Low Acceptable for most pedestrian areas
45+ Low (very good) Suited to high-risk wet/ramped areas
Slider rubber Simulates Typical use
Slider 96 (Four S) Shod (footwear) Most floors — shops, kitchens, entrances
Slider 55 (TRL) Barefoot Pool surrounds, showers, changing rooms
DIN R-rating (51130, oil-wet ramp) Indicative use (manufacturer figure only)
R9 Dry internal areas, entrance halls
R10 Kitchens, WCs, general wet-prone
R11 Commercial kitchens, workshops, external
R12–R13 Heavy contamination, food production

R-ratings are not equivalent to PTV and do not prove in-situ safety. Where slip risk matters, verify by pendulum to BS 7976.

Detailed Guidance

How the pendulum works

A weighted arm with a rubber slider swings down and skims across the floor surface over a set contact length. Friction between slider and floor slows the swing; the height the arm reaches on the upswing is read on a scale as the PTV. Higher friction = bigger slow-down = higher PTV = more grip. Because it is the dynamic friction of a "heel" striking and sliding, it reflects the real mechanism of a slip far better than a static drag test.

Decision tree — specifying a floor for slip safety:

Will the floor get wet or contaminated in use?
  |
  +-- NO  -> dry PTV >= 36 is generally sufficient
  |
  +-- YES -> test/specify WET PTV with the right slider:
             |
             +-- shod area (Slider 96): aim WET PTV >= 36
             +-- barefoot area (Slider 55): aim WET PTV >= 36
             |
             +-- viscous contaminant (oil, grease, soap)?
                 -> higher surface roughness (Rz) also needed

Wet vs dry, and choosing the slider

Always think about the worst realistic condition. A polished porcelain that gives PTV 40 dry can collapse to single digits wet — which is why entrances, wet rooms and kitchens must be assessed wet. Use Slider 96 (Four S) for areas used in footwear and Slider 55 (TRL) for barefoot areas like shower floors and pool surrounds. Quoting a single dry number for a wet area is meaningless and indefensible.

Where slip resistance is non-negotiable

Entrances (water walked in from outside), commercial and domestic kitchens, bathrooms and wet rooms, ramps and sloped approaches, swimming pool surrounds, and accessible routes under Part M. For wet rooms and bathrooms in particular, specify a tile or sheet with a verified wet PTV ≥ 36 and detail the falls and drainage so water clears — see wet room installation guide, wet room flooring and bathroom floor tile layout. For ramps and level changes, slip resistance combines with the gradient and edge-protection rules in Part K — see building regs part k and part k falls.

R-ratings: useful, but know their limits

DIN 51130 R-ratings (R9–R13) come from a tester walking an oiled, tilting ramp in boots and recording the angle of slip — a lab comparison for shod areas. DIN 51097 (A/B/C) is the barefoot equivalent for pools. They are handy for shortlisting products and writing a first-pass spec, but they are not measurements of your floor as laid, with your contaminant, after wear. They are not what the HSE or a court will rely on. Treat an R-rating as a starting filter and verify the real risk with a pendulum PTV.

Surface roughness and the contaminant

Slip resistance in the wet depends heavily on micro-texture, measured as surface roughness (Rz, in microns). The thicker (more viscous) the contaminant, the more roughness you need for the asperities to break through the liquid film and make contact. Clean water needs less roughness than cooking oil or soap suds. Where heavy or greasy contamination is expected, do not rely on PTV alone — consider Rz as well and choose a finish accordingly. See resin flooring guide and epoxy coatings for resin systems where aggregate broadcast controls both PTV and Rz.

Maintenance changes the number

A floor's slip resistance is not fixed. Polishing by foot traffic, the wrong cleaning regime, grease build-up, worn anti-slip aggregate and over-burnished finishes all drop the PTV over time. If you specify a floor to a target PTV, hand over a cleaning/maintenance note so it stays at that level, and recommend periodic re-testing in high-risk areas.

Frequently Asked Questions

What PTV do I need for a wet floor?

Aim for a wet PTV of 36 or above, measured with the appropriate slider (96 for shod areas, 55 for barefoot). 36+ corresponds to a low slip potential. Below 25 is high risk and needs remedial action. Between 25 and 35 is a grey zone that should be improved or actively managed.

Is an R11 tile safe for a wet room?

Not necessarily. R11 is a manufacturer's oil-wet ramp figure for shod use; a wet room is often barefoot and uses water/soap, not oil. The honest answer is to specify and, where it matters, verify a wet PTV with the barefoot (Slider 55) rubber. R-ratings help you shortlist but do not prove the floor is safe as laid.

Who can do a pendulum test?

A competent person with a pendulum tester calibrated and used to BS 7976, following the UKSRG operating guidelines (correct slider, conditioning, contact length, multiple readings and directions). For specification you can rely on manufacturer pendulum data; for a dispute or post-incident assessment, use an independent, suitably accredited tester.

Does the law require a specific PTV?

The Workplace (Health, Safety and Welfare) Regulations 1992 require floors to be suitable and not a slip risk, rather than naming a number. The HSE then uses the pendulum and the 36/25/24 PTV bands to judge whether that duty is met, so in practice the PTV bands are the working benchmark.

How does this relate to accessibility (Part M)?

Part M and inclusive-design guidance call for slip-resistant surfaces on entrances, accessible routes and ramps, and for surfaces to remain slip-resistant when wet. Combine a verified wet PTV with the gradient, landing and handrail rules. See part m access.

Regulations & Standards