The short answer
Good composite decking is usually less slippery than timber, especially once timber has gone green. Like any outdoor surface it can be slippery when wet, icy or dirty. Choose capped boards with a textured surface and published slip test results, and keep the deck clean.
Slippery decking is one of the most common reasons people pull up an old timber deck. So it is a fair question to ask before paying for a new one. The short version: composite is usually the safer choice, but not all boards are equal, and how the deck is looked after matters as much as what it is made of.
Why decking gets slippery
Most slips on decking come from the same few causes:
- Algae and moss. Damp, shady decks grow a thin green film that is very slippery when wet.
- Water sitting on the surface. Grooves and poor drainage hold water.
- Ice and frost on winter mornings.
- Dirt, leaves and grease left on the boards.
Timber suffers most from the first cause. It absorbs water, stays damp, and gives algae a good surface to grow on, especially in the shady corners of a garden.
How composite compares with timber
Composite boards are made from wood fibre and plastic. Capped composite adds a hard plastic outer shell, which:
- absorbs very little water, so it dries faster
- gives algae less to cling to
- can be moulded with a textured, grippy surface
That is why capped composite decks usually stay less slippery than timber over the years. Older or cheaper uncapped boards and some smooth finishes can still be slippery when wet, so the board you choose matters.
What slip ratings mean
The pendulum test is the method the UK’s Health and Safety Executive prefers for measuring slip resistance. It gives a Pendulum Test Value (PTV). Marley’s guidance, citing UK Slip Resistance Council standards, says a PTV of 36 or more means a surface has a low potential for slip.
When comparing boards, look for:
- a published wet PTV, not just a dry one
- testing by an independent laboratory
- results for the actual board and finish you’re buying
A maker that has nothing published is a reason to ask questions.
How to choose non-slip composite decking
- Capped boards with a textured or embossed surface.
- Wet slip test results of 36 PTV or more.
- Lighter colours in shade, so you can see dirt and algae building up.
- Good drainage: a slight fall away from the house and gaps between boards kept clear.
- Safe steps: contrasting nosings and a handrail where there is a drop.
On a sloping Sheffield garden, where decks often have steps and changes in level, the steps deserve as much thought as the boards.
Steps: the riskiest part of any deck
Most falls on decking happen on steps rather than on the flat. Steps are often in shade, collect leaves and water, and are where people are carrying things or looking elsewhere. To make them safer:
- keep every step the same height and depth, so feet find them without looking
- use contrasting or anti-slip nosings on the front edge of each step
- add a handrail where there are more than a couple of steps or a drop beside them
- light steps you use after dark with low-level step lights
- keep steps clear of pots and leaves
Keeping a composite deck safe
- Clean it at least twice a year, more often in shade. Our cleaning guide covers how.
- Sweep leaves before they sit and rot on the boards.
- Grit icy mornings with white salt rather than rock salt, and clear snow with a plastic shovel, as Millboard’s care guide advises.
- Trim back overhanging plants so the deck gets light and air.
Is timber ever less slippery?
A brand-new, clean timber deck with anti-slip inserts or grooved boards can be safe. The problem is keeping it that way. Timber needs regular cleaning and treatment to stop algae taking hold, and many timber decks that start out fine are slippery a few years later. If slips are a worry, composite is usually the lower-maintenance way to a safe deck. Read our composite vs wood decking comparison for the full picture.
Ask about grip before you buy
When you get quotes, ask each installer:
- which boards they recommend for grip, and why
- whether those boards have independent wet slip test results
- how they will handle steps and level changes
- what cleaning the maker recommends
If you’re planning decking in Sheffield, the quote form takes two minutes. Mention in the notes if slips are a worry, and the installer can bring samples to the visit.