Stair Nosing Slip Resistance: PTV and R Ratings Explained
Two numbers get quoted for stair nosing slip resistance. They measure different things, they are not interchangeable, and only one of them is recognised by the HSE.
Getting this wrong is how a stair that looks well specified on paper turns out to be dangerous in the rain.
The two tests
| Pendulum Test Value (PTV) | R rating | |
|---|---|---|
| Standard | BS 7976, now BS EN 16165 | DIN 51130 |
| Method | Swinging arm with a rubber slider | Person walks a tilting ramp until they slip |
| Contaminant | Water | Motor oil |
| Footwear | Standardised rubber slider | Safety boots |
| Can be tested in situ | Yes | No, laboratory only |
| Recognised by the HSE | Yes, the preferred method | No |
Why they do not convert
People ask for a conversion table constantly. There is not one, and any supplier offering you a clean conversion is overstating what the data supports.
The reason is that the tests model different scenarios. The ramp test uses motor oil and safety boots, which describes a factory floor. The pendulum uses water and a rubber slider, which describes a person in ordinary shoes on a wet day. A surface can perform very differently under those two conditions.
The practical consequence: a single R10 rating can correspond to pendulum results anywhere from about 20 to 60 — that is the full span from high slip potential to low. An R rating on its own tells you remarkably little about how a stair behaves in the rain.
The PTV scale
The HSE and the UK Slip Resistance Group band wet pendulum results like this:
- 0–24 — high slip potential
- 25–35 — moderate slip potential
- 36 and above — low slip potential
PTV 36 wet is the benchmark to specify against. Where oil, grease or food waste is likely, specify 65 or above.
Note the emphasis on wet. Almost every surface passes dry, so a dry PTV is close to meaningless as a safety figure. If a supplier quotes only a dry value, ask for the wet one.
What the R scale is good for
R ratings are not useless. R9 to R13 is a genuinely informative shorthand where oil rather than water is the contaminant — commercial kitchens, food production, engineering workshops. R11 and above is the usual industrial specification.
The correct approach is to ask for both figures, and to treat a supplier who can only produce one as having given you half an answer.
Typical performance by material
- GRP — the highest wet grip of the common nosing materials. Published UK supplier data puts GRP nosings around 65–69 PTV wet, with some silicon-carbide products above 80. See the GRP range.
- Aluminium with a PVC or carborundum insert — performance depends almost entirely on the insert, not the metal. Good inserts clear 36 wet comfortably. See the aluminium range.
- Ribbed brass and bare metal — moderate dry, weaker wet. Fine on interior stairs away from entrances; the wrong choice for external steps.
- Rubber and PVC — good when new, but performance falls as the surface wears smooth.
Performance degrades — and the duty does not
This is the part most specifications ignore. Regulation 12 of the Workplace (Health, Safety and Welfare) Regulations 1992 requires that floors are not slippery so as to expose anyone to risk. It applies continuously, to the surface as it is today.
A nosing that tested at 45 PTV when installed may be well below 36 after a decade of polishing, or after two winters of algae in an unwashed external stairwell. The certificate from installation does not discharge the duty.
Because the pendulum can be used in situ, periodic testing on the installed surface is how you evidence continuing performance. That is a real advantage over the ramp test, which only ever describes a sample in a laboratory.
Frequently asked questions
What PTV should I specify?
At least 36 in the wet for general use, and 65 or above where oil, grease or food waste is likely.
Is R11 good enough?
For an oil-contaminated industrial floor it is a reasonable shorthand. For a rainy external stair in ordinary shoes it does not describe the relevant condition. Ask for the wet PTV as well.
Can I convert an R rating to a PTV?
No. The tests use different contaminants and different footwear, and a single R band spans a very wide range of pendulum results.
Which figure would matter if something went wrong?
The pendulum test value. It is the method the HSE recognises and the one used to assess slip risk in UK workplaces.
Does a dry PTV mean anything?
Very little on its own. Almost all surfaces perform well dry. Slips happen when a surface is wet or contaminated, which is what the wet test measures.
How often should a stair be retested?
There is no fixed interval. On a stair where slip risk has been formally assessed, periodic in-situ testing is sensible — particularly on external stairs and anywhere the surface is visibly polishing.
See the full compliance guide, or browse anti-slip stair nosings by material.