Short answer
The best way to clean timber decking is to sweep it, clear the gaps between the boards, then scrub along the grain with a stiff brush and a cleaner made for decking before rinsing well. You can jet wash decking, but only on a low setting with a wide fan, held well back and moved along the grain, because a close jet tears up the wood fibres and leaves the boards rough and furry.
Check the deck before you clean it
Walk the whole deck first. Press on boards that look dark or soft, check for loose or raised screws, and look at the joists you can see at the edges. Cleaning will not fix rot or a loose board, and water from a hose or pressure washer can make a weak area worse. Repair or replace anything unsafe before you start.
Find out what the deck is made of. This guide covers timber. Composite boards look similar but need a different approach, which our guide to cleaning composite decking explains. Also note whether the timber has been stained, oiled or painted, because a worn finish will look patchy once the dirt has gone.
What you will need
A stiff broom, a putty knife or thin scraper for the gaps, a bucket, a stiff synthetic scrubbing brush on a long handle, a garden hose and a decking cleaner suitable for your timber. Avoid wire brushes, which scratch the boards and can leave metal fragments that rust. Wear gloves, eye protection and shoes with good grip, because wet decking is slippery.
Move furniture, pots and barbecues off the deck. Cover plants close to the edges, or soak them with plain water before and after so any run-off is diluted.
How to clean decking by hand
- Sweep off leaves, soil and loose debris, working along the length of the boards.
- Run the scraper along each gap to pull out packed leaves and dirt, so water can drain and air can circulate under the boards.
- Test the decking cleaner on a small board in a corner and let it dry so you can see the result.
- Wet the deck, then apply the cleaner following the manufacturer's dilution and contact-time instructions. Never mix cleaning products.
- Scrub along the grain, a few boards at a time, paying extra attention to shaded areas, steps and the boards nearest the house.
- Rinse thoroughly with the hose until the water runs clear.
- Leave the deck to dry completely before putting furniture back or applying any oil, stain or protective treatment.
Can you jet wash decking?
You can, but timber is soft compared with paving, and how you use the machine makes all the difference. Choose a low pressure setting and a wide fan nozzle, never a pinpoint or rotating turbo nozzle. Start with the lance well back from the boards, try a hidden section first, and only move closer if the dirt is not shifting.
Keep the spray moving along the grain in long, even passes from one end of a board to the other. Stopping in one spot, or sweeping across the grain, leaves lines and gouges that are hard to hide. If the surface starts to look fuzzy, you are too close or the pressure is too high. Lightly sanding raised fibres once the deck is dry can smooth them again.
Pressure washing does not replace a cleaner. Algae often grows back quickly if it is only blasted off the surface, so many people apply a decking cleaner first and use the pressure washer for the rinse.
Cleaning decking without a pressure washer
For most decks, a stiff brush, a suitable cleaner and some effort do a good job, and there is far less risk of damaging the wood. A long-handled brush saves your back, and working in sections stops the product drying before you rinse. Grooved boards need scrubbing along the grooves rather than across them, so the bristles reach the bottom of each channel.
Keeping decking less slippery
Decking turns green fastest where it stays damp: under trees, in shade beside a fence or wall, and where the gaps are blocked. Keeping the gaps clear, trimming back overhanging growth and sweeping regularly all help the boards dry out. A light scrub now and then is much easier than tackling a deck that has been left for several seasons.
If you want to oil or stain the timber after cleaning, check the product instructions for how dry the wood needs to be first.
When to call a professional
Consider calling a professional if the deck is large, raised or has lots of steps, if the algae comes back soon after every clean, or if you are not confident using a pressure washer on timber. It is also worth having boards checked if you suspect rot, as cleaning should not be confused with repairing a deck.
When we clean decking, we look at the boards first and agree the approach for your deck once we have seen it. We remove green algae and the grime trapped in the board grooves, include steps and edges by agreement, and can add a biocide treatment where algae is the recurring problem.
Rather have it done for you?
Timber and composite decking cleaned of green algae and slippery grime. Family-run by Jason and Lucas Prior, covering south Essex.
Frequently asked questions
What is the best way to clean decking?
Sweep, clear the gaps, then scrub along the grain with a stiff synthetic brush and a cleaner made for decking, and rinse well. It is slower than jet washing but gentler on the timber.
Can you jet wash decking?
Yes, on timber, if you use a low setting and a wide fan nozzle, keep the lance well back and move along the grain. Too much pressure leaves the boards rough and furry.
Can I use bleach on decking?
Bleach can discolour timber and harm plants and lawn nearby, so a cleaner made for decking is a better choice. Whatever you use, follow the label, test a small area first and never mix products.
Related guides
- How to clean composite decking: gentle cleaning for composite boards, including stubborn spots, grease and the pressure-washing question.