How to clean a deck without ruining it
Too much pressure leaves a deck furry, rough and patchy when you oil it. How to clean timber along the grain, and why it has to dry before the oil goes on.
The assumption we're testing
“Turn it up to full and the grey comes straight off.”
Why decks go furry
Timber has hard lines of grain with softer wood in between. A strong jet tears out the soft wood and leaves the hard lines standing. That rough, hairy look is called furring.
Once a deck is furry, it needs sanding before it can be oiled again. Skip the sanding and the oil soaks in unevenly, so the boards go patchy.
Clean first, then rinse
The grey on an old deck is mostly worn timber and mould. A timber cleaner loosens it and kills the mould. Give it time to work.
Then rinse at low pressure. Keep the nozzle moving. Run it along the length of the boards, with the grain, never across it. Hard timber can take a little more. Even then, less is safer.
Let it dry before you oil
Wet timber won't take oil. Oil put on too soon sits on top, stays tacky and can peel.
Give the deck a few dry days after cleaning. Check the weather first, since rain in that window starts the clock again. How long it takes depends on the timber, the sun and the shade.
Treated pine, composite and stairs
Treated pine is soft, so it furs easily. Keep the pressure low. Composite decking is plastic and wood fibre mixed. Check the maker's care guide first, since the wrong cleaner or too much pressure can void the warranty.
Stairs and rails get done by hand. Wet timber is slippery, so take care on the steps while the work is on.
Our deck cleaning page has more detail. Or get a free quote, and we'll tell you when your deck will be ready to oil.
Want it done without the risk? We'll check the surface first, then pick the method.