What Makes Non-Slip Shoes Non-Slip: Sole, Tread and Test

by YDA UK

A shoe is non-slip because of three things working together: the material of the outsole, the pattern cut into it, and the floor it meets. Change any one and the grip changes. That is why no shoe is “non-slip” on every surface, and why a label alone never settles the question.

Below we explain each factor, how grip is measured, what the SRA and SRB marks really tell you, and how to check a pair yourself before you rely on it.

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TL;DR

  • Grip comes from the outsole compound, the tread geometry and the surface (wet, oily, tiled, outdoors), not from one “magic” feature.
  • Softer, well-chosen compounds and close-packed, well-channelled treads generally hold better on wet indoor floors. Open treads suit outdoor ground and solid debris.
  • Test results (coefficient of friction, SRA and SRB) are lab figures. The HSE says trialling shoes in the real workplace is the reliable check.
  • “Oil-resistant” does not mean “slip-resistant”, and grip fades as the sole wears.

Table of Contents

The short answer: material, pattern, surface

Slip resistance is a friction problem. When your heel lands, the sole has to grip the floor before a film of water, grease or soap lets it skate. Researchers describe the result as an interaction between the outsole material, the tread pattern and the surface, which is how the HSE’s footwear guidance frames it too.

So when someone asks what makes a shoe non-slip, the honest answer is a list of design decisions, each aimed at a particular kind of floor.

Factor 1: the outsole material

The compound is the first thing that matters. Hard, shiny plastics skid on wet tile. Compounds that stay slightly compliant let the sole conform to tiny irregularities in the floor and keep contact.

Material choice can make a measurable difference. A 2022 study using geometrically controlled outsoles found polyurethane (PU) outsoles gave 61 to 125% higher dynamic friction than vulcanised rubber on contaminated surfaces. Because the tread geometry was held constant, the difference came from the material.

Hardness matters as well. A study that measured slip resistance across materials, tread designs and contaminants identified both sole hardness and tread geometry as significant factors.

What this means when you shop:

  • Rubber or PU soles are the usual starting point, but the specific compound counts more than the name.
  • A sole that feels very hard and glossy in the hand is rarely the grippiest on a wet floor.
  • Marketing words such as “grip” or “traction” tell you little. Ask for a test result or a rating.

Factor 2: the tread pattern

Tread does two jobs. It gives edges that bite into the floor, and it channels liquid out from under the sole so the shoe is touching the floor rather than floating on a film.

Close-packed or open?

The HSE notes that tread designs are not one-size-fits-all: close-packed patterns tend to work better on indoor floors with fluid contaminants, while open patterns do better outdoors or around solid debris because they clog less. A kitchen and a muddy yard need different soles.

Grooves and channels

Grooves that run out to the sole’s edge give liquid somewhere to go. A sole with shallow, closed-off pattern traps water and behaves like a smooth one. The angle of channels matters too: a 2024 laboratory study of 24 outsole designs varied tread angle, thickness and gap width to see how each changed traction.

Mixing rough and smooth

Some of the most interesting work uses hybrid surfaces. A study of an outsole with tread blocks and a hybrid rough-and-smooth rubber surface examined whether it could raise slip resistance on contaminated floors. The wider materials and tread research reports that such hybrid patterns outperformed conventional designs in reducing slips on contaminated surfaces.

Factor 3: the surface and what is on it

Factor 3: the surface and what is on it — overview diagram

The same shoe behaves very differently from floor to floor. Friction is usually expressed as a coefficient of friction (COF): the higher the number, the better the grip.

In the controlled study mentioned above, mean COF was about 0.85 on dry floors, about 0.44 on wet ones and as low as 0.08 with glycerol on the surface. Those figures come from one set of test conditions, so treat them as an illustration of the spread, not a promise for any particular shoe. They do show why a pair that feels secure in the shop can be treacherous on an oily kitchen floor.

Surface Typical challenge What helps most
Dry indoor floor Low risk, but polished surfaces can still be slick A compliant sole, clean tread
Wet tile Thin water film Close-packed tread, channels, softer compound
Oily or greasy floor Lubricating film Compound and pattern tested for oil, good drainage
Outdoor, mud, leaves Solid debris that clogs Open, deeper tread
Ramps and slopes Higher friction demand Higher-grip compound, intact tread

How slip resistance is tested

Manufacturers measure grip by pushing a shoe or sole sample across a test floor with a contaminant and recording friction. Whole-shoe methods such as ASTM F2913 are described as reproducible laboratory tests for evaluating relative slip performance. European work-footwear testing follows EN ISO 13287, and the HSE explains that ratings such as SRA, SRB and SRC reflect results on ceramic tile wetted with soap solution, on steel with glycerol, or both.

How slip resistance is tested — overview diagram

The European Agency for Safety and Health at Work’s OSHwiki gives a wider overview of how many different methods and devices exist, which is one reason numbers from different labs are hard to compare directly.

What the marks mean in practice

  • SRA: tested on ceramic tile with a soapy water solution.
  • SRB: tested on smooth steel with glycerol, a much slipperier test.
  • SRC: passed both.

The marking scheme for safety footwear has been revised in recent versions of the standard, so the letters on an older pair may not match what a new pair carries. Read the label and the manufacturer’s explanation rather than assuming.

Is there a magic number?

A COF of 0.5 is often quoted as a benchmark. The US regulator is clear that it is a guideline, not a mandate: OSHA has no standard requiring a particular COF for walking surfaces. Tasks such as walking up ramps or pushing heavy loads can demand more. In Great Britain the duty sits with the employer to assess risk and choose suitable footwear.

“Oil-resistant” is not “slip-resistant”

This is the most common mix-up. According to the HSE, oil-resistant means the sole material will not degrade when exposed to oil. Slip resistance depends on the specific tread and compound combination designed for that environment. A sole can shrug off oil chemically and still skate on it.

Grip fades: wear and replacement

A non-slip sole is not non-slip forever. The HSE points out that performance degrades as the outsole wears and the tread smooths out, and that employers need a system to monitor wear and replace footwear before its safety properties are lost.

A simple home check:

  1. Turn the shoe over and look at the tread under bright light.
  2. Check whether grooves have worn shallow or the pattern has gone flat at the heel and ball of the foot.
  3. Look for hardening, cracking or a glazed, shiny sole.
  4. Clear packed-in grit or grease with a brush and warm soapy water.
  5. If the heel is worn unevenly, replace the pair, as the heel strike is where most slips begin.

How to check a pair before you trust it

The HSE’s own advice is that standard laboratory surfaces do not capture every real-world variable, so the reliable confirmation is a trial in the actual workplace. The same logic applies at home or on the school run.

  1. Name your floor. Wet tile, greasy lino, polished stone, wet pavement and a frosty path need different things.
  2. Look at the sole. Visible channels, a pattern that reaches the edge, and a compound that is not rock hard.
  3. Ask for the test evidence. A rating or a named test method beats a vague “anti-slip” claim.
  4. Try it on the real surface. Walk slowly, then turn, step down and stop. Note any skating at the heel.
  5. Check fit. A shoe that moves around on the foot makes you compensate and slip, whatever the sole.
  6. Plan to replace it. Treat the sole as a consumable.

If you want to go deeper, our own guides cover what makes a shoe non-slip, the three evidence-backed factors on the shop floor, anti-slip shoes, SRA/SRB tests and employer duty and different types of shoe soles.

Our perspective

We look at grip as part of how the whole shoe supports the foot, not just as a patch of rubber. A sole can have a good pattern and still let you down if the shoe is unstable, the foot slides inside it or the heel rolls on landing. That is why we pay attention to how each step is stabilised, which is the idea behind our YDA technology.

Our advice is plain. Be wary of any single claim, ours included, that promises grip everywhere. Match the sole to the floor, check wear regularly, and see how a shoe feels on the surface you actually walk on. People with problem feet or diabetes have a particular reason to care: a slip is more costly when your feet are already vulnerable, and they should take advice from a podiatrist or their diabetes foot-care team on footwear. We also explain why good grip matters for safety and health for that reason.

— Panagiotis

If you want support and grip in one shoe

Our footwear is built for everyday wear with comfort, foot health and energy efficiency in mind, and with specialist options for people with conditions such as diabetes. Stock changes often, so check availability. Browse the range on the Ydauk shop or read how the technology in YDA shoes works before you choose.

FAQ

Are non-slip shoes the same as slip-resistant shoes?

In everyday use, yes. Neither means a shoe cannot slip. Both mean the sole has been designed, and ideally tested, to grip better than an ordinary sole on specified surfaces. Ask what surface and test the claim refers to.

Does a deeper tread always grip better?

No. Deep, open tread suits mud and debris, but on wet indoor floors the HSE says close-packed patterns tend to work better. The compound and how the pattern drains liquid matter as much as depth.

How long do non-slip soles last?

There is no fixed figure, because it depends on how often you wear them, the floors and how you clean them. The HSE notes that grip degrades as the sole wears, so inspect the tread regularly and replace the shoes once it has smoothed out.

Can I make my existing shoes less slippery?

Cleaning grease and grit from the sole helps, and roughening a glazed sole is sometimes suggested, but neither restores a worn compound or a flattened pattern. If the tread has gone, replace the shoes. At work, your employer should provide suitable footwear following a risk assessment.

What is a good coefficient of friction for shoes?

A COF of around 0.5 is often used as a rule of thumb, but OSHA describes it as a guideline, not a mandate. Demanding tasks such as ramps need more, and the value depends on the test method and floor.

Sources

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