How to clean composite decking

How do you clean composite decking?

Sweep off leaves and grit, wash with warm water and a mild soap or detergent using a soft brush, then rinse. That’s the method Millboard, Envirobuild and Cladco describe, and it’s usually all you need. Clear the gaps between boards so water can drain. Makers that mention direction say to spray or scrub along the grain.

One UK owner who skipped the pressure washer, because her deck sat over a pond liner, used hot water, washing-up liquid, a soft brush and a mop to lift the dirty water as she went. It removed most of the green and black mould, though the boards weren’t spotless, and she plans to repeat it yearly rather than let it build up.

Can you pressure wash composite decking?

Many makers allow it, with limits, and the limits don’t match. Use a fan tip, keep the nozzle back and test a hidden spot first.

If you don’t want to use one at all, you don’t need to. The brush method above works.

Which decking cleaner should you use on composite?

Start with soap and water. The maker guides we read mostly don’t name a branded cleaner. Wickes says composite needs no specialist product, and Eurocell says not to use chemical products on its hollow boards. Eva-Last goes further for its Apex board: don’t use standard composite deck cleaners on it, and avoid strong detergents, oxidisers, concentrated mineral acids, solvents and undiluted chlorine.

If you do buy a decking cleaner, check three things on the label: that it says it’s safe for composite, that your maker doesn’t ban that type, and that you can rinse it fully. Test it on an offcut or a hidden corner. The widely sold decking cleaners are mostly made for timber. Ronseal’s decking cleaner, for example, is a timber product.

How do you remove mould and algae from composite decking?

Start with the soap and brush method. If black or green patches stay, Composite Prime suggests an organic patio cleaner such as Algon, or a sodium percarbonate oxygen bleach, then rinsing off all the detergent. Trex says to remove pollen and debris and scrub with warm soapy water and a soft brush. Cladco’s Signature guide says apply soapy water or Cladco cleaner, scrub, leave it for 60 minutes and rinse.

Mould feeds on dirt, so the real fix is keeping the deck clear. Shady corners and spots under pots stay damp the longest.

How do you remove stains from composite decking?

Test every product on a hidden patch first, as several of these makers say.

What should you do in winter?

Use a plastic shovel, not a metal one, on snow and ice. De-icers are where makers disagree:

• Millboard says a small amount of granulated white salt is fine, and rock salt isn’t because it contains clay and grit.
• Composite Prime and Trex say calcium chloride or rock salt will do.
• Envirobuild says avoid calcium chloride because it can leave marks.
• Eva-Last says calcium or sodium chloride may be used, which can leave white residue, and that grip is reduced when the deck is icy.

You’ll have to choose one maker’s advice, so choose yours.

Why does new decking look oily, and does the colour change?

New Millboard can look oily or shiny from a manufacturing release agent that weathers off in 6 to 8 weeks. Guardian says initial lightening evens out over 8 to 10 weeks. Composite Prime says colour pigments stabilise in the first 6 to 12 months. A US decking retailer suggests keeping a spare offcut indoors, so you can see how much the deck has shifted after years.

How do you look after composite decking day to day?

Furniture and planters need rubber or felt feet, and dragging things scratches the surface. Millboard warns about unprotected furniture legs, spiked shoes, animal claws and metal planter bases. Move furniture now and then so the boards weather evenly, as Eva-Last advises. Eurocell says no single item over 100 kg and no dragging furniture across hollow boards.

How do you clean timber decking?

Different rules apply. See timber decking for bleach, washing powder and pressure-washer settings that only suit wood.