How to clean decking: wood, composite and PVC

Why does decking become slippery?

Algae, moss, dirt and decaying leaves can form slippery deposits, particularly in damp or shaded areas. Timber and synthetic decking both need cleaning; low-maintenance does not mean maintenance-free. The Timber Decking and Cladding Association explains the role of surface deposits.

Removing build-up can help reduce one cause of slipperiness. It does not make a deck slip-proof, repair damaged boards or eliminate risks from rain, frost and ice. Restrict access if the deck is unsafe and arrange an assessment rather than trying to clean it while standing on a dangerous surface.

Before you start: identify and inspect the boards

Check whether you have softwood or hardwood timber, wood-plastic composite, PVC or another manufactured decking product. Find the brand and product range if possible. A woodgrain appearance alone does not identify the material. Coatings, caps and older product generations can change the cleaning method.

Look for loose or soft boards, splinters, protruding fixings and movement. Cleaning cannot repair rot or an unsound substructure. Stop and seek a competent repair assessment where there are signs of deterioration. Photograph the whole deck, a board close-up and any problem areas from a safe position.

How to clean wooden decking

1. Remove loose debris. Clear leaves and dirt with a suitable non-metal brush. Move furniture only if safe, keeping a clear exit and avoiding trip hazards.
2. Check the timber and finish. Follow the board supplier’s and any stain or oil manufacturer’s guidance. A mild soap solution or compatible timber-deck cleaner may be suitable for routine washing.
3. Try a small area. Test the cleaner and brush in an inconspicuous place. Check that the finish is not lifting and the timber is not roughening.
4. Clean manageable sections. Follow the product label for dilution, protective equipment, contact time and rinsing. Do not mix products or improvise a bleach-and-chemical recipe.
5. Let it dry and inspect. Assess the dry result before deciding whether another treatment is needed. Oiling, staining, sanding and repairs are separate maintenance decisions, not automatic parts of a wash.

The TDCA’s timber-deck maintenance guidance supports regular debris removal and appropriate washing, with caution over power spraying.

How to clean composite, PVC and synthetic decking

Use the care instructions for the exact product, including its recommended brush and cleaner. Do not transfer a timber-cleaning method to a capped composite or PVC board without checking compatibility.

Trex’s care guide, for example, distinguishes newer product ranges from early-generation composite boards. Some ranges permit careful pressure washing; early-generation Trex decking is not recommended for pressure washing. Sanding is not a general solution for a marked composite surface.

TimberTech’s guidance also varies by material and product generation. Brush recommendations for Advanced PVC differ from those for composite, and some cleaners described as “composite deck cleaners” are unsuitable for its current capped products.

Where directed, wash in small sections and rinse thoroughly before the cleaner dries. Protect nearby plants and other surfaces according to the product instructions. Do not assume synthetic boards need timber oil or stain. Millboard has its own product-care guidance; its instructions should not be applied to every synthetic deck.

Can you pressure wash decking?

Sometimes—but “decking power washing” is not a safe method specification by itself. Excessive pressure, a concentrated jet or an incompatible cleaner can damage the surface or affect the warranty. A pressure setting suitable for one manufacturer’s board is not a universal setting.

If the exact product’s guidance permits it, follow both that guidance and the equipment manual, including the nozzle, distance and technique. Test first. Stop if fibres lift, the finish changes or the board is damaged. If you cannot identify the product or a sound method, use professional advice rather than increasing the pressure.

Keeping algae and slippery build-up under control

Regularly remove leaves and soil, watch shaded areas and follow the manufacturer’s maintenance schedule. Keep accessible drainage gaps clear without damaging the boards or fixings. Persistent puddling or an unstable deck needs investigation, not repeated cleaning alone.

Cleaning products, hoses and wet surfaces create their own hazards. Keep children and pets away during work, protect electrical equipment, and avoid cleaning in freezing conditions. Plan runoff and disposal before starting; do not wash detergents or contaminated water into ponds or surface-water drains. See Environment Agency pollution-prevention guidance.

When to ask for professional decking cleaning

A large deck, heavy growth, awkward access or uncertainty about the boards can make an assessment worthwhile. For decking cleaning across Cornwall, send Kernow Clean the postcode, approximate area, material or brand if known, and clear photographs. Include water availability and any damage or existing coating.

Our real project results include a timber-decking transformation. The outcome for your deck depends on its material and condition; cleaning is not a promise of structural repair or a slip-proof finish.

For adjacent areas, see how to clean a patio and how to clean uPVC fascias, soffits and house plastics.

Sources are linked beside the relevant advice. Manufacturer instructions take priority; source links do not imply an endorsement of Kernow Clean.