Anti-Slip Paving and R-Ratings, Explained

An R-rating grades how slip-resistant a tile surface is, measured by the DIN 51130 ramp test: an operator in standard boots stands on an oiled sample as its angle increases, and the angle at which they slip sets the class. The scale runs R9 to R13 — R9/R10 suit interiors, R11 is the common specification for UK outdoor paving (patios, paths, pool surrounds), and R12/R13 are industrial grades. There is no R1–R8; the scale starts at 9.

R-ratings vs the UK pendulum test (PTV)

The UK's preferred measure for pedestrian surfaces — used by the HSE and in BS 7976 — is the pendulum test, which swings a rubber slider across the wet surface and reports a Pendulum Test Value. PTV 36 and above is classed as low slip potential. R-ratings and PTVs come from different tests and don't convert exactly, but both appear on tile datasheets; an outdoor-textured slab specified for wet external use will typically carry an R11 class and a wet PTV in the low-slip band.

How anti-slip porcelain works

The slip resistance is in the fired surface texture — a micro-rough finish that keeps grip when wet — not a coating that can wear off. That's why the same porcelain colour is often made in more than one finish (smooth for indoors, textured/anti-slip for outside), and why an outdoor finish keeps its rating for the slab's life with nothing to re-apply.

What to specify where

• Patios, paths, dining terraces: an outdoor textured finish — commonly R11 — is the sensible default in a wet climate.
• Pool surrounds, hot-tub aprons, steps: treat anti-slip as mandatory: barefoot, wet and gravity all at once.
• Driveways: texture matters less for tyres than for the humans walking on it — same rule as patios.
• Natural stone: slip resistance varies by finish here too — riven and sandblast textures grip well; honed surfaces are smoother. Check the finish, not just the stone.

Check the rating per product, not per material

"Porcelain" and "sandstone" as categories have no slip rating — individual products and finishes do. Check the specific listing for the finish and any published slip class of the exact pack you're ordering. Pave Direct's outdoor porcelain ranges — including Kandla Grey — are supplied in anti-slip textured finishes, collected under the anti-slip porcelain hub.

Grip is also a laying and upkeep property

Two non-product factors decide real-world slipperiness: falls (a 1:80 drainage gradient stops water sheeting and standing — see the laying guide) and algae (the green film, not the tile, causes most winter slips — see cleaning porcelain).