Pressure Washing · Service

Deck cleaning, without shredding the boards

Wood is the one surface that is walked on like a driveway and damaged like siding. Get matched with crews who know which of those two facts governs your deck — and who will tell you when the boards are past cleaning.

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In short

What is deck cleaning?

Deck cleaning removes the algae, mildew, ground-in dirt and greying film that build up on a wood or composite deck, usually as preparation for sealing or staining rather than as an end in itself. The defining constraint is that timber is soft and fibrous: enough force to lift dirt off the surface also tears the wood fibres beneath it. Competent deck cleaning is therefore mostly chemistry, gentle agitation and rinsing, with pressure used sparingly if at all.

Triggers

Signs you need deck cleaning

The boards are slippery underfoot after rain, particularly in the shaded run along a wall or under a tree canopy
There is a dark green or grey-black film that dulls the whole surface rather than sitting in patches
Water no longer beads on the boards but soaks straight in and darkens them
You can see a distinct clean rectangle where a planter, a grill or a furniture leg has been sitting
Moss or dark growth is packed into the gaps between boards and around the fasteners
You are booked in for a stain or a sealer and the installer has said the deck must be cleaned and dry first

Seeing something not on this list? Browse pressure washing problems by symptom →

The job

How deck cleaning actually works

Establish what the deck is made of, and how sound it is

Pressure-treated pine, cedar, a tropical hardwood and a composite board all behave differently under both water and chemistry. Before anything is applied the crew should also be looking for loose boards, proud fasteners, soft spots at the joist line and rot at the posts.

Watch for: A composite deck treated as if it were timber. Composite carries its own manufacturer care instructions, and the wrong cleaner or too much force can permanently mark the cap layer. Hand those instructions over if you still have them.
Clear the deck and protect what surrounds it

Furniture, grills, planters and rugs come off entirely rather than being shuffled around, because a half-cleared deck cleans in patches. Planting beneath and beside the deck is soaked first, and anything growing through the structure gets particular attention because runoff concentrates there.

Watch for: Planters left in place "to save time". You will see their outlines in the finished surface for the life of the boards.
Apply the cleaner and let it lift the growth

A deck cleaner is applied across the whole surface and given time to work on the biological film and embedded dirt. Where the growth is heavy, a stiff brush on a pole does the mechanical work that a pressure washer would otherwise do — with far less consequence for the fibre.

Watch for: Cleaner allowed to dry on the boards, and spot-treating one bad area only. Both leave the deck two-tone once dry, and on wood a patchy clean shows up dramatically the moment stain goes on.
Rinse with the grain, at low pressure and constant distance

Where pressure is used at all on timber it is a wide fan held well back and moved continuously along the length of the board, never held still and never worked across the grain. On composite it is gentler still. The rinse runs until the water coming off the boards is clear.

Watch for: A narrow tip, a close hold, or an operator stopping mid-board. Each gouges softwood in about a second, and the marks are in the timber permanently.
Let it dry fully, then decide about coating

Wood needs to dry through, not just look dry, before a sealer or stain will bond. Between cleaning and coating is also when you find out whether the boards have raised grain that needs sanding back.

Watch for: A same-visit seal upsell. Sealing over a damp board traps moisture under the coating, and the coating fails early and blotchily — which then has to be stripped before you can try again.

Money

What does deck cleaning cost?

Deck cleaning is priced by deck area after the boards are seen, with steps, railings, spindles and lattice adding hand-work rather than square footage. Heavy growth, stripping an old failed coating, and any sanding are separate items. The Cost Guide sets out how these stack.

See the full deck cleaning cost guide — by material, size and region →

Exterior cleaning tools → Measure the deck field, steps and railings before you take quotes.

Straight answer

When deck cleaning is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

The deck is unsafe rather than dirty. Spongy boards, movement underfoot, rot where the ledger meets the house, or corroded fasteners are a structural matter. Cleaning a failing deck makes it look serviceable when it is not, which is the worst possible outcome. Have it inspected first.
You want the silver-grey colour reversed. Greying is ultraviolet degradation of the wood surface, not dirt. Cleaning removes the growth and the film on top of it and the grey largely stays. Restoring colour means a brightening step and then a pigmented coating — a different job with a different price.
There is a sound coating you like on the boards. A cleaner strong enough to shift growth will also dull, lighten or blotch an intact stain or sealer. If the finish is doing its job, wash gently or leave it and clean when the coating is due to be renewed anyway.
The boards are already fuzzy from a previous washing. Once the fibres are torn, more washing raises more fibre. That deck needs sanding before it needs cleaning again, and sanding a deck is carpentry, not exterior cleaning.
Freezing weather or a wet week is forecast. Timber that cannot dry out between cleaning and coating stays wet in the joints, and a deck that is washed and then left damp for a fortnight can come back with more growth than it started with.

Straight answer

Can I do this myself?

The real hazard on a deck is not the machine, it is the surface. Wet boards with cleaner on them are genuinely slippery, and decks have edges, steps and drops. Rinse as you go, wear grippy footwear, and never work backwards towards an unguarded edge.

Reasonable to DIY

Sweeping the gaps between boards clear of packed debris with a thin blade or a putty knife before any water goes on
Applying a proprietary deck cleaner per its own label and agitating with a stiff deck brush on a pole
Rinsing with a garden hose, which is enough for a lightly soiled deck and cannot damage anything

Call a licensed pro

Any deck where you suspect structural problems — that is an inspection, not a wash
Stripping a failed stain or sealer, which is a chemical process with its own neutralising and rinsing requirements
Tropical hardwoods and capped composites, where the margin between clean and marked is small and the boards are expensive
Elevated decks where the underside, the skirt and the posts also need attention and you would be working off a ladder

Before you sign

What to check when hiring for deck cleaning

Will you use pressure on my boards at all, and if so at what distance and which tip?

The most predictive question you can ask about a deck. "Mostly chemical, brushed, rinsed at a wide fan from well back" is the professional answer. Enthusiasm about pressure is a warning.
Is the cleaner you use compatible with what is on my deck now, and with what is going on next?

Some cleaners leave residue that interferes with coatings, and some strip more coating than you expect. The crew should be thinking about the finish that follows, not just today's appearance.
Are railings, spindles, steps and the skirt included, or only the deck field?

Detail work is where the hours go, and it is the most common quiet exclusion. A freshly cleaned floor between grubby railings looks worse than not cleaning at all.
What happens if a board comes up fuzzy or gets marked?

You want to hear that it should not happen and what they would do if it did. A contractor who has never had to answer this has either never damaged a deck or never been asked.
How long do you want the deck to dry before anything is applied to it?

If the answer is "a few hours, we can seal the same day", stop. Timber holds water for longer than its surface suggests, and premature coating is the most common cause of a deck finish failing in its first season.
How do you protect the planting under and around a raised deck?

Runoff from a deck concentrates at the drip line and straight through the gaps onto whatever is beneath. Beds under a deck take a heavier dose than beds beside a wall.
Do you also strip and sand, or do you hand that off?

Establishes the boundary of the job up front. Plenty of good cleaning crews do not sand — the problem is only when you find that out on the day the stainer arrives.

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Local pros

Deck Cleaning near you

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Related work

Often done at the same time

Fence Cleaning

The same timber problem, standing up

Soft Washing

Why chemistry beats force on soft surfaces

Driveway & Flatwork Cleaning

The flatwork the deck sits next to

Deck Inspection

If the boards feel wrong underfoot, start here

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FAQ

Deck Cleaning — questions people ask

Still have a question? Talk to our team →

Why did my deck go fuzzy after it was washed?

Because the water tore the wood fibres rather than cleaning them. Softwood decking has a fine surface that lifts under concentrated force, and once lifted it dries standing proud — which is the fuzz you can feel. It is not dirt and it will not rinse off. The fix is sanding the surface back — realistic on a flat deck field, awkward on railings and spindles.

Should the deck be cleaned before staining, or is that an upsell?

It is genuine and it is not optional. A stain or sealer bonds to the wood, and anything sitting between the two — mildew, a dust film, an old degraded coating, mill glaze on new boards — becomes the weak layer the finish peels away from. Most coating failures that look like "bad stain" are failures of preparation. Ask whoever is coating what surface condition their product specification requires, and have the cleaning done to that standard.

Can a composite deck be cleaned the same way as a wood one?

Not automatically. Composite decking is a manufactured product with published care instructions, and those instructions are the governing document — some limit pressure explicitly and some rule out particular cleaner types. The general failure mode is different too: rather than raising fibre, excess force on composite can dull or scar the cap layer in a way that shows in raking light forever. Find the manufacturer's care guide if you can and give it to whoever is quoting.

How often does a deck need cleaning?

It tracks shade, moisture and tree cover far more than a schedule. A deck in full sun stays acceptable for a long time; one under a canopy can go green within a single damp season. The practical trigger is slipperiness, or a coating falling due — cleaning is the preparation, so it rides the sealing cycle.

Will cleaning get rid of the moss between the boards?

It removes what is growing there, but the gaps are the reason it came back, and cleaning does not change the gaps. Debris packs into the joints, holds moisture against the board edges and gives moss somewhere permanent to live. Clearing the gaps physically, and keeping them clear, does more for the life of the boards than the wash itself.