Last updated: 29 September 2026 · By the Tiles & Pavers team, Knutsford, Cheshire
Quick answer: No — outdoor porcelain paving is not slippery when it is correctly specified and kept clean. Look for a slip resistance rating of R11 or higher (DIN 51130) for patios and paths. Polished or smooth indoor tiles should never be used outside. Most slips on patios are caused by algae, moss and wet leaves, not by the porcelain itself.
Key takeaways
- R11 is the sensible minimum for outdoor porcelain in the UK.
- Choose R12 or a textured finish for slopes, steps, pool surrounds and shaded areas.
- A UK Pendulum Test Value (PTV) of 36+ indicates low slip potential in wet conditions.
- Keep the surface free of algae — no rating can overcome a green, slimy film.
Why do people think porcelain is slippery?
Porcelain is famous for smooth, glossy indoor floors, so many people assume outdoor porcelain will be the same. It isn't. Outdoor porcelain paving is manufactured with a textured, anti-slip surface and is tested for grip in wet conditions. Problems usually happen when indoor tiles are used outside, when a patio has too little fall so water sits on it, or when algae is allowed to build up.
What does the R rating mean?
The R rating comes from the German ramp test DIN 51130. A tester in safety footwear walks on an oil-covered sample while the ramp angle is gradually increased. The angle at which they start to slip decides the rating:
| Rating | Ramp angle | Slip resistance | Typical use |
|---|---|---|---|
| R9 | 6°–10° | Low | Dry indoor areas (e.g. polished floor tiles) |
| R10 | 10°–19° | Moderate | Kitchens, bathrooms, light-moisture indoor areas |
| R11 | 19°–27° | Good | Outdoor patios, paths, terraces |
| R12 | 27°–35° | High | Ramps, steps, pool surrounds, driveways |
| R13 | >35° | Very high | Industrial and specialist areas |
What is the Pendulum Test Value (PTV)?
In the UK, slip resistance is often measured with a pendulum test, which swings a rubber slider across a wet surface to mimic a heel striking the ground. The result is a Pendulum Test Value (PTV). A PTV of 36 or more is generally classed as low slip potential. The R rating and PTV are different tests, so they don't convert exactly, but a good-quality R11 outdoor porcelain will typically sit in the low-slip-potential band when wet.
Which slip rating do I need?
- Flat patio or garden path: R11.
- Steps, slopes or ramps: R11 minimum, R12 preferred. Use bullnose step treads for a safe, finished edge.
- Pool surrounds and hot-tub areas: R11–R12 with a textured finish.
- North-facing or tree-shaded gardens: R11 or above, plus a regular cleaning routine.
- Driveways: a structured or textured R11–R12 surface; see our driveway range and driveway tile guide.
You'll find the slip rating in the specification section of each product page. If it is not listed, ask our team before you order.
Does the finish or colour affect grip?
Yes. Structured, grip or "anti-slip" finishes have a micro-texture you can feel under your fingertips. Very smooth "natural" or matt finishes can look similar but feel different, so always check the rating rather than judging by eye. Colour does not change grip, but very pale slabs show algae sooner, which is a useful early warning to clean. The best test is to order a free sample, wet it and try it with your own shoes.
How to keep a porcelain patio non-slip all year
- Build in a fall of about 1:60–1:80 away from the house so water runs off rather than pooling.
- Sweep leaves regularly, especially in autumn — wet leaves are slippery and stain.
- Treat algae early with a suitable outdoor cleaner. Our porcelain cleaning guide explains how.
- Seal cement-based grout joints to reduce moss growth between slabs.
- Avoid wax or gloss sealers on porcelain — they can reduce grip.
Frequently asked questions
Is porcelain paving slippery when wet?
Outdoor porcelain paving rated R11 or higher is designed to give good grip when wet. Smooth indoor porcelain can be slippery outdoors and should not be used there. Algae, moss or leaves can make any patio slippery.
What does R11 mean on porcelain paving?
R11 is a slip resistance class from the DIN 51130 ramp test. It means the surface kept grip up to a ramp angle of 19–27 degrees in contaminated conditions, which makes it suitable for outdoor patios and paths.
Is R10 porcelain OK for outdoors?
R10 is intended mainly for indoor areas that occasionally get wet, such as kitchens and bathrooms. For open-air patios in the UK, R11 is the recommended minimum.
Can I make existing porcelain paving less slippery?
First, deep-clean it to remove algae and residue, which is the usual cause. If the tiles are genuinely too smooth for outdoor use, anti-slip treatments exist, but replacing them with an R11 outdoor slab is the most reliable fix.
Is porcelain paving safe for children and older people?
Yes, when you choose an R11 or R12 outdoor slab, build in a proper fall and keep it clean. A textured finish is a good choice for family gardens and around steps.
Choose with confidence: browse our outdoor porcelain paving and order up to 3 free samples to test the grip at home.