Three common anti-slip surfaces

FRP grating uses three main anti-slip surfaces: the concave profile formed during moulding, a grit surface where hard particles are bonded into the resin, and a diamond plate bonded to pultruded grating. The first two dominate molded grating; the third is common on pultruded walkways and stair treads.

They grip in different ways. A concave surface keys into the sole by geometry, grit provides micro-roughness through exposed particles, and diamond plate breaks the liquid film with raised ridges. Different mechanisms suit different contaminants, so they cannot be ranked by roughness alone.

For the full range of surfaces, grit grades and panel types, see the anti-slip FRP grating

How the concave surface works

The concave surface is formed in the mould as the panel cures, usually 0.5 to 2 millimetres deep, giving a regular pattern of hollows across the grid. It adds no extra process, is the most common standard finish and is what a quotation assumes unless told otherwise.

Grip comes from the sole mechanically keying into the hollows. That is enough when dry, lightly wet or dusty, but mud, oil or ice can fill the hollows, and once they are filled the surface behaves much like a flat plate while still looking unchanged.

The concave surface is also easy to clean; washing and brushing restore it. It is uncomfortable under bare feet, so it is rarely chosen for public areas or poolside. It suits industrial walkways, equipment platforms and general access.

Depth and shape are set by the mould and vary little between makers, but panel thickness changes the relative depth of the hollows. Judge from a physical sample rather than the depth figure on a drawing.

Grit: wet and oily duty

A grit surface is made by broadcasting hard particles, usually quartz or alumina, onto the resin before it cures, so each particle is partly encapsulated and partly exposed. Grip comes from the exposed particles, not from the resin.

Grit is clearly more reliable with oil, slurry, food residue or on a slope. The micro-roughness pierces the liquid film so the sole reaches the solid surface instead of floating on the liquid; food plant washdown areas and docks are typical uses.

Grit has costs. It wears soles faster and makes trolleys and pallets harder to push; it is unsuitable for bare feet, seated work and dragging heavy loads. Particles also trap dirt, so cleaning takes more water than a concave surface and residue can become a hygiene problem.

Grit does come off. The rate depends on how well the resin encapsulates the particles, the particle size and the intensity of use, and grip falls after loss even when the change is not visible. On high-risk sites, grit condition belongs in the inspection routine rather than being checked after an incident.

Diamond plate

Diamond plate is usually bonded to the top of pultruded bearing bars or formed directly into stair treads. The raised ridges give point contact and drain quickly, so a continuous liquid film does not build up.

Diamond plate is directional. It is easier to slip along the ridges than across them, so the ridge direction relative to the walking direction matters, especially on stair treads and ramps.

The surface is flat and easy to clean, which suits food, pharmaceutical and frequent washdown areas. Its slip rating is usually below a grit surface, and it is less reliable under heavy oil contamination, so a neat appearance is not evidence of better grip.

Fixings must be dependable. If adhesive or mechanical fixing fails, the plate edge lifts and becomes a trip hazard; on stair treads this is critical, and every plate should be checked along its edges after installation.

Assessing a wet environment

Wet is too broad a word for slip assessment. Water, oil, soap, slurry, ice and food residue differ in viscosity and affect the surface differently. Oil and soap are hardest because they form a continuous film that separates sole from surface.

Three questions matter: what the contaminant is, at what concentration and temperature, and how often it is cleaned. Clean water and oily wastewater place completely different demands on the surface; a concave finish often copes with the first, while the second usually needs grit.

Site testing is closer to reality than laboratory data. A portable pendulum gives a friction value at the time of test, but the result depends on cleanliness, temperature and the operator, so it informs the choice rather than replacing selection by duty.

Slope amplifies risk. The same surface needs a higher friction coefficient as the slope rises from zero to five degrees, so ramps, stairs and loading edges should be selected for the worst case rather than from flat-floor experience.

Barefoot and booted: two standards

Slip testing splits into booted and barefoot methods. DIN 51130 uses an oiled ramp and a standard boot and reports R9 to R13; DIN 51097 uses bare feet and soap solution and reports A, B or C.

The methods differ, so the grades do not convert. R11 does not mean safe barefoot, and class A does not mean adequate for boots on an oily slope. Decide who will be walking first, then read the matching grade.

Poolside, showers and water parks follow the barefoot standard; factories, docks and wastewater plants follow the booted standard. Where both occur, apply the stricter class or choose different surfaces by zone.

Cleaning and grit wear

Slip resistance is consumable. Hollows fill, grit wears away and diamond ridges round over, and the rating falls. Cleaning is not only hygiene; it maintains grip, so the cleaning interval belongs in the maintenance plan.

Match the cleaning method to the surface. Grit tolerates low-pressure water and a soft brush, while a high-pressure jet held close will strip particles faster. Concave surfaces take a stiff brush, but not metal tools that scratch the resin.

Use neutral detergents. Strong acid or alkali attacks the resin, loosens the bond around the particles and speeds loss; solvent cleaners can bleach or soften the surface. Rinse the residue away with clean water so a slippery film is not left behind as it dries.

Selection and specification wording

State the surface type, particle material and size, required slip class, service environment (water, oil, soap, barefoot or booted), cleaning method and slope. An inquiry that says only anti-slip leaves the supplier quoting the default grit finish, which may be neither suitable nor easy to accept.

Panel depth, bar spacing and fixing, beyond the surface itself, follow the FRP grating specification guide

Stairs, ramps and loading edges also need tread depth, drainage and handrail coordination; see the stair and tread solutions

• Fix the contaminant and the user before the surface.
• Prefer grit for wet, oily and sloping duty.
• Use DIN 51097 for barefoot areas.
• Write cleaning and inspection into the maintenance plan.