Decking, whether timber or composite, needs regular cleaning to stay safe underfoot as much as to look good, since algae buildup on decking boards makes them genuinely slippery, not just unsightly. Decking cleaning cost varies by material and whether oiling is included, and getting the method wrong can do real damage to the boards themselves.
This guide covers per-m² pricing for both timber and composite decking, what oiling adds, and how to make sure the method used is safe for the specific material you have in the garden.
Decking cleaning prices
For a standard timber deck, cleaning typically costs £4-£8 per m², or roughly £120-£280 for an average garden deck around 20-30m², depending on soiling level and how much moss or algae has taken hold in the grain. Composite decking is similarly priced, generally £4-£7 per m², though it needs a gentler approach since the surface can be more susceptible to scratching from overly aggressive brushing or pressure.
Heavily soiled decking that's been neglected for a few years, with slippery green algae throughout, sits at the higher end of the range since it typically needs a specific decking-safe cleaning product left to dwell before rinsing, rather than a quick surface pass.
Oiling add-ons for timber decking
Once timber decking is cleaned and fully dry, applying a decking oil or stain protects the wood, enhances its colour, and helps repel water, which slows down future algae growth. This typically adds £3-£6 per m² on top of cleaning, so a full clean-and-oil package for a medium deck might run £200-£400.
Composite decking doesn't need oiling since it's not a natural wood product, but some composite ranges benefit from a specific protective treatment recommended by the manufacturer, which is worth checking rather than assuming it's identical to timber care.
Safe pressure levels by material
Timber decking, particularly softwood, is vulnerable to pressure washing at too high a setting, which can score the surface grain, leaving a fuzzy, damaged texture (sometimes called 'washboarding') that's hard to reverse. A lower pressure setting with an appropriate dwell-and-rinse cleaning product gets a better, safer result.
Composite decking is more resilient to moderate pressure but can still be scratched or discoloured by an incorrect nozzle or excessive pressure held too close, so manufacturer guidance (many composite brands specify a maximum safe pressure) is worth following, and a professional familiar with composite decking will already know this.
Getting decking ready for the season
A clean before the decking sees heavy summer use makes practical sense, both for safety underfoot and to catch any early signs of rot or damage on timber decking while there's still time to address it before winter weather makes things worse. It's a good moment to check for loose boards or popped fixings at the same time.
For timber decking specifically, cleaning and oiling together, rather than as separate jobs weeks apart, gives the best result, since oil applied to a freshly cleaned, fully dry surface penetrates and protects far more effectively than oil applied over old, weathered wood.
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