Slip resistance ratings tell you which surface and which lubricant a safety boot’s outsole was tested against. Under EN ISO 20345:2011 the codes were SRA (ceramic tile with a dilute soap solution), SRB (steel floor with glycerol) and SRC (both tests passed). The 2022 edition replaced those three codes with a single SR marking. Knowing which system a certificate uses tells you whether the rating you are being sold actually matches the floor your team works on.
Slip and trip incidents are consistently among the most expensive categories of workplace injury — not because the boots were cheap, but because the specification was written around a code rather than a floor. This guide explains what each rating tested, why the 2022 revision consolidated them, what actually determines grip in service, and how to write a slip requirement that survives a tender review. For the models we hold with the current SR marking, see our certificates listed by model and class.
Why slip resistance belongs in the purchase specification
Footwear is the last line of defence against a slip, and it is the control that procurement actually owns. Flooring, drainage, cleaning regimes and contamination are managed by other people; the outsole is what the buyer can specify, test and reject against. That makes the slip code one of the few clauses in a footwear spec with a direct line to incident cost.
The failure mode is rarely “the boot had no rating at all”. It is that the rating described a surface nobody works on. A boot certified for grip on wet ceramic tile tells you nothing about grip on a steel plate coated in hydraulic oil, and a code alone says nothing about how the outsole behaves once the tread has worn down or the floor has been treated with a degreaser.
The legacy codes: SRA, SRB and SRC
Under EN ISO 20345:2011, slip resistance was reported as one of three codes. Each corresponds to a specific combination of test surface and lubricant, and each carries its own minimum coefficient of friction for the heel and for the flat of the sole.
| Code | Test surface | Lubricant | What passing means | Typical application |
|---|---|---|---|---|
| SRA | Ceramic tile | Dilute soap solution | The outsole met the minimum coefficient of friction on a wet, smooth tiled surface | Food plants, commercial kitchens, washdown areas, hospitals |
| SRB | Steel floor | Glycerol | The outsole met the minimum on a smooth metal surface lubricated with glycerol | Industrial flooring, workshops, engineering, loading bays |
| SRC | Both | Both | Both SRA and SRB were passed, so the boot carries no surface limitation | Mixed sites, and the default most buyers specified under the 2011 edition |
SRC became the de facto requirement in most tenders because it removed an argument: a boot certified SRC had been tested on both surfaces, so the buyer did not need to know which surface dominated the site. That convenience is also why the code outlived its usefulness — it told you the boot passed two tests, but not how well it performed on either one.
What changed in EN ISO 20345:2022
The 2022 edition consolidated the three codes into a single marking:
- SR is now the slip resistance marking under EN ISO 20345:2022. Instead of reporting which of two optional surfaces was tested, the current edition treats slip resistance as a requirement that the footwear either meets or does not, and marks it accordingly.
- SRA, SRB and SRC did not disappear from circulation. They remain on certificates and on boots manufactured and certified under the 2011 edition. Stock with an SRC label is not non-compliant — it is simply labelled under the older system.
- The edition on your certificate determines which code is meaningful. If a supplier quotes SRC on a certificate that cites EN ISO 20345:2022, ask to see the test report. If the certificate cites the 2011 edition, SRC is the correct code for that document.
Practically, this means you should stop specifying “SRC” as a blanket requirement and start specifying the current edition plus the SR marking, with the test report attached. Our own certification illustrates the transition: the LT-601 design holds S4 FO SR and S5 FO SR under separate certificates, and the LT-102-22 design holds S5 SR FO under EN ISO 20345:2022+A1:2024. Full details are on the certifications page.
What actually determines grip in service
The rating is a laboratory result on a new outsole. Real grip depends on four things the code does not describe, and they are worth asking about separately.
| Factor | Why it matters | What to ask the supplier |
|---|---|---|
| Outsole compound | Different polymers behave very differently on the same floor. PVC holds up well against water, dilute acids and alkalis; nitrile rubber compounds are generally chosen where oils, fats and solvents are present; polyurethane keeps weight down and resists abrasion but is less tolerant of some wet, hot environments. | Which compound is used, and was the tested sample the same compound as production? |
| Tread pattern and depth | The pattern channels the lubricant away from the contact patch. A shallow tread that grips well when new can lose most of its effectiveness once worn. | Tread depth, and whether the certified sample used the production tooling |
| Temperature | Compounds stiffen as temperature falls, and a stiffer sole conforms less to the floor. This is why cold stores need a compound chosen for low-temperature flexibility, not just a CI marking. | Which compound and which low-temperature behaviour is claimed |
| Contamination type | A code earned with glycerol does not describe behaviour in hydraulic oil, animal fat, flour dust or a degreaser. The test lubricant is a proxy, not your floor. | Measured values, and whether testing covers your actual contaminant |
The most useful request you can make is not “send the certificate” but “send the measured coefficients”. Minimum thresholds are defined in the test method rather than in the product standard, so a pass/fail line tells you the outsole cleared a bar — it does not tell you by how much. A supplier who can show the measured figures for both the heel and the flat of the sole is giving you something you can compare across models.
Writing a slip requirement that survives a tender review
A clause that just says “SRC” is easy to satisfy and hard to enforce. A clause that names the edition, the marking, the document and the measured values gives you something to reject against at goods-in. Adapt the following:
All safety footwear shall conform to EN ISO 20345:2022 and shall carry the SR slip resistance marking recorded on the EU type-examination certificate. The supplier shall provide, for each model offered, the full slip resistance test report from an accredited laboratory, showing the measured coefficient of friction for both the heel and the flat of the sole. The certified sample shall be of the same outsole compound, tread pattern and tooling as production units. Where the working environment contains oils, fats or solvents, the supplier shall state the outsole compound selected for that exposure and provide supporting evidence.
Three things in that clause do the work: it names the edition (so the code system is unambiguous), it requires measured values rather than a pass line (so models can be compared), and it ties the certificate to production tooling (so the sample tested is the boot delivered).
Where the environment is dominated by water rather than oil — food processing, agriculture, washdown areas — pair the slip requirement with the right class of polymer boot. Our industrial PVC rain boots buying guide covers that selection in detail, and the PVC rain boots category shows the styles built for wet, chemical and washdown work.
Frequently asked questions
Is SRC still valid, or do I have to ask for SR?
Both codes are legitimate on the documents they were issued under. SRC belongs to EN ISO 20345:2011 and means the boot passed both available slip tests. SR is the marking used under EN ISO 20345:2022. If you are writing a new specification, ask for the current edition plus SR; if you are assessing existing stock or a certificate issued under the 2011 edition, SRC is the correct code to read.
Does a slip rating guarantee the boot will not slip?
No. A slip rating is a laboratory result for a new outsole on a defined surface with a defined lubricant. Grip in service also depends on the compound, the tread pattern and its remaining depth, the temperature, and the actual contaminant on the floor. Treat the rating as a baseline requirement and the measured test values as the comparison tool.
Should I ask for measured friction values instead of a pass/fail result?
Yes, where the supplier can provide them. Minimum thresholds are set in the test method, so a pass line only tells you the outsole cleared a bar. Measured coefficients for the heel and the flat of the sole let you compare two certified models and judge which has more margin on your surface.
Which outsole compound is best for oily floors?
Where oils, fats and solvents dominate, nitrile rubber compounds are generally specified over standard PVC, because hydrocarbons attack PVC compounds differently. The important step is to confirm that the compound quoted is the one that was tested, since a certificate does not automatically cover every compound a factory can mould.
How does slip resistance relate to the S-classes such as S4 and S5?
The S-class and the slip marking are separate parts of the same marking string. The class — SB through S5 — describes the baseline package including toe protection, antistatic performance, water behaviour and penetration resistance. Slip resistance is an add-on marking such as SR that must appear on the same certificate. A boot can be S5 without SR, and a class alone never implies slip performance. For the full list of codes and classes, see our EN ISO 20345 boot code guide.
Further reading
- ISO 20345 – the international standard for safety footwear
- UK Health and Safety Executive – Slips and trips – assessment and floor contamination guidance
- European Commission – PPE Regulation (EU) 2016/425 – the conformity route behind the certificate
