Is composite decking slippery when wet? Grip, winter and how to build for it

"Is composite decking slippery when wet?" is the question people ask after a winter on timber, when green boards under a frost put someone on the ground. The honest answer is that composite is safer than timber in the wet, but no outdoor surface is slip-proof in ice, and the face you lay up, the way you build the deck and what you do in November all change the answer. This guide covers grip on our boards, the choices that improve it, and how to keep a deck usable through a British winter.

The short answer

Wet, our boards grip better than wet timber, because the surface is textured plastic rather than an open grain that holds algae. The grooved face gives more grip than the woodgrain face; lay it up on steps, ramps and the path from the door. Build in a fall so water runs off, keep the surface clear of leaves and algae, and in frost use rock salt or grit sand, which composite tolerates and timber does not.

Why timber is slippery and composite less so

A timber board has an open grain that soaks up water, and in shade that damp grain grows a film of algae that is as slippery as ice. Composite is roughly half plastic. It does not absorb water, so the surface dries faster, and algae only sits on top where the spring wash removes it. Both faces of our boards are textured: the woodgrain face is embossed, the grooved face is ridged. Neither is the smooth, film-coated surface that makes some decking and most tiles treacherous.

Grooved or woodgrain: which face is safer

The grooved face, and it is not close. The ridges channel water away and give a foot something to bite on. That is why it exists. The woodgrain face is fine on a deck that gets sun and dries between showers; on a north-facing deck, a set of steps or a walkway that is used in the rain, put the grooves up. You can mix faces board by board, so a woodgrain deck with grooved steps and a grooved path to the door is a normal build. The face guide covers the trade-offs.

Build choices that improve grip

• A fall of 1 in 100 away from the house. Standing water is the enemy; a slight slope clears it. This is set in the frame, not the boards.
• Grooves running with the fall, not across it, so they drain rather than hold water.
• 40mm of air under the deck. A ventilated deck dries from below as well as above.
• Cut back overhanging trees. Drip and leaf litter are what turn a shaded deck green.
• Step edges with a nosing. Our step edge boards have a rounded, grooved front so the edge of each step is grippy and visible.
• Light and mid colours on steps in a dark corner, so the edge can be seen.

Autumn: the season that causes most slips

Wet leaves on any surface are slippery, and rotting leaves feed algae. Sweep the deck every week or two from October, and do the autumn wash once the leaves are down. A deck that goes into winter clean stays grippy; one that goes in under a mat of leaves is green by February. The routine is in how to clean composite decking.

Frost and snow

• Salt is fine. Rock salt or a calcium chloride de-icer will not harm a composite board. Sweep the residue off in spring. Do not use salt on a timber frame if it can reach it; it will not hurt a composite or plastic frame.
• Grit sand gives instant grip on ice and sweeps off later.
• Plastic shovel for snow. A metal shovel scratches the surface.
• Do not chip ice. Salt it and wait.
• No rubber-backed mats left down over winter. They trap water and can mark the surface. Use an open-weave outdoor mat and lift it now and then.

Anti-slip strips and coatings

Stick-on anti-slip strips work on steps and are cheap; put them 50mm back from the nosing on the grooved face. Anti-slip paints and coatings are made for timber and do not bond well to composite; most peel within a season and make the surface worse. If a deck needs a coating to be safe, the problem is usually drainage or algae, and fixing that is the better spend.

Is composite decking safe for older people and children?

Safer than timber and safer than most patio stone, provided it is built with a fall, kept clean and salted in frost. For a deck used by someone unsteady on their feet, lay the grooved face up everywhere, fit a balustrade on any raised edge (required by building regulations above 600mm anyway), use step edge boards, and put a light on the steps. None of that is specific to composite; it is what makes any outdoor surface safe.

Checklist for a deck you can use all year

1. Grooved face on steps, ramps and the walkway.
2. Fall away from the house, grooves running with it.
3. Sweep from October, wash in April and October.
4. Salt or grit in frost, plastic shovel for snow.
5. Step edge boards and a balustrade on anything raised.

Order free samples, wet them and stand on both faces. It is the fastest way to settle the question for your own garden.