How to clean composite decking

Video by NeoTimber. This guide draws on the "How To Clean Your NeoTimber® Composite Decking" video from NeoTimber, a composite decking manufacturer based in Coalville, Leicestershire. They cover the cleaning process from sweep to scrub to rinse, with good detail on what to avoid. Worth a watch before your first clean to make sure you are not using anything that could mark the boards.

1. Clear the deck completely

Move all furniture, plant pots, and anything else off the boards before you start. Cleaning around obstacles means you miss spots, and those missed spots will be obvious once the rest looks fresh.

While you have everything off, take a moment to check the gaps between boards for trapped leaves and debris. A flat-bladed scraper or a purpose-made composite deck cleaner tool gets this out far more effectively than a brush.

2. Sweep thoroughly

Brush the deck down firmly with a stiff-bristled brush, working along the grain of the boards. Composite boards have a wood-effect texture and cleaning across it pushes dirt into the grooves rather than lifting it out.

Pay particular attention to shaded areas and anywhere near planters. Those spots collect the most moisture and are where algae takes hold first. If you spot any green growth, it will need more than a sweep — that is dealt with below.

3. Mix the right cleaning solution

For a routine clean, warm water and a small amount of washing-up liquid is all you need. Mix it in a bucket rather than spraying undiluted cleaner directly on the boards.

Do not use bleach, white spirit, acetone, or any solvent-based cleaner. These can strip the colour from the surface, leave permanent marks, or compromise the board's UV coating. That said — for green algae specifically — a dedicated composite deck cleaner or a diluted specialist algae remover is worth it rather than fighting it with soap alone.

4. Scrub along the grain

Apply the solution with a scrubbing brush, working in the direction of the board’s wood grain. Use firm, even strokes. You are not trying to sand the surface, just lift the grime that has settled into the texture.

Do not use wire wool, abrasive pads, or a rotary scrubber. These scratch the surface in a way that catches dirt more readily afterwards and can be impossible to reverse. Soft-bristled brushes only.

5. Rinse thoroughly

Rinse the boards thoroughly with clean water. A garden hose on a moderate setting works well. A pressure washer can be used on the lowest setting — mind you, some manufacturers specifically advise against it, so check your deck’s documentation first.

If you do use a pressure washer, hold it at least 30 cm from the surface and work along the grain. Never angle it into the gaps between boards or directly at the board ends — that forces water under the frame and causes issues in cold weather.

6. Tackle stubborn stains individually

Oil, grease, and food stains need dealing with quickly rather than left to the main clean. A small amount of washing-up liquid worked in with a soft cloth usually does it if caught early. Dried food residue responds well to a few minutes of soaking with warm soapy water before scrubbing.

For tannin stains from fallen leaves or tree droppings — common in Kent gardens in autumn — a specialist composite deck stain remover is the most reliable option. These are available from most builders’ merchants and larger DIY stores.

7. Let it dry and replace the furniture

Let the deck dry completely before putting the furniture back. Walking on a wet composite deck with rubber-footed furniture can leave marks in certain finishes, and trapped moisture under planters slows drying and encourages mould to return.

Once a year, after the clean, is a good moment to check the fixings and the subframe. Composite boards last well but the timber joists underneath do not always get the same maintenance attention. Poke the joists with a screwdriver. Any soft spots are worth dealing with sooner rather than later.

When to call a handyman

Call Richard if the subframe looks questionable, the boards have lifted or warped due to moisture getting in, or if you want a reliable annual clean done properly. Green algae can make composite decking genuinely slippery, and getting it off well does make a difference to how long the deck looks good.