TL;DR
Deck cleaning is a low-pressure job that relies on chemistry rather than force. It typically covers the deck boards, railings, spindles, stairs, and the area beneath, using a cleaner with dwell time to release algae, mildew, and greying, followed by a gentle rinse. Sealing and staining are separate work that happens after the wood has dried fully, usually days later.
Why High Pressure Ruins Wood Decks
Wood is not a uniform material. Each growth ring has dense latewood and softer earlywood, and pressure erodes the soft part first.
The result is a furred, fuzzy surface with visible ridges -- the wood equivalent of sanding with the wrong grit. It looks acceptable when wet and terrible when dry. Worse, a furred surface holds water and dirt better than a smooth one, so the deck gets dirty faster afterward and any stain applied over it absorbs unevenly.
Pressure damage on a deck is also permanent short of sanding the boards down. There is no cleaning process that undoes it.
So professional deck cleaning uses low pressure with a wide fan tip held well back, or no pressure at all beyond a rinse, with a sodium percarbonate or specialty deck cleaner doing the work. Dwell time replaces force.
What Does a Deck Cleaning Service Cover?
It typically covers sweeping and clearing the surface, pre-wetting surrounding plants, applying an appropriate cleaner to boards, railings, spindles, stairs, and the fascia board, allowing dwell time, gentle agitation with a soft brush, and a low-pressure rinse. Brightening with an oxalic solution is often included on wood. Sealing, staining, sanding, and board replacement are separate work.
Clearing debris from the gaps between boards is part of a proper job and is frequently skipped -- packed debris in those gaps traps water against the board edges, which is where rot starts.
Wood Versus Composite
The two materials need different handling and produce different expectations.
Wood decks -- cedar, redwood, pressure-treated pine, and hardwoods like ipe -- grey over time from ultraviolet exposure. That greying is surface oxidation of the wood fibers, and a deck cleaner plus a brightener usually restores much of the original tone. Hardwoods are dense and respond well; softwoods need gentler handling.
Composite and PVC decking does not grey but does develop mold and mildew, particularly in the embossed grain texture where spores settle. Composite is cleaned with a dedicated composite cleaner rather than a wood product, and the manufacturer's guidance governs -- some warn against certain chemicals and against pressure entirely, and using the wrong thing can void a warranty. Early-generation composite is more prone to staining and mold than newer capped boards.
Both materials benefit from having furniture, planters, and mats moved, since anything sitting on a deck leaves a mark.
What Cleaning Does Not Fix
Setting expectations here saves disappointment.
Weathered grey that goes deep. A brightener restores the surface, but a deck left untreated for many years may need sanding to reach sound wood, and that is refinishing work.
Tannin bleed and iron stains. Black streaks around fasteners are rust reacting with wood tannins. An oxalic brightener helps considerably, but corroded fasteners keep producing them until they are replaced.
Rot and soft boards. Spongy boards, soft rails, and any movement in the structure are carpentry. Cleaning them is pointless and standing on them is unsafe.
Failing stain or sealer. A peeling finish has to be stripped or sanded, not washed. Washing a peeling deck lifts more of it unevenly, which makes the eventual strip harder.
Deep gouges and splinters. These are sanding and board replacement.
Any competent provider should walk the deck first and tell you which of these apply. A structural check matters too: loose railings, corroded joist hangers, and a ledger board separating from the house are safety issues that a cleaner may notice but a deck contractor should assess.
Sealing Is a Separate Job
This is the most common misunderstanding about deck services.
Cleaning and sealing are two jobs with a mandatory gap between them. After washing, wood has to dry thoroughly before any sealer or stain goes on -- typically two to three days of dry weather, sometimes longer for dense hardwood or in humid conditions. A moisture meter is the reliable check.
Sealing over damp wood traps moisture, which causes cloudiness, poor adhesion, and premature failure. It is the single most common reason a newly finished deck looks wrong within a season.
That gap is why cleaning and sealing are usually booked as two visits, and why the weather forecast matters when scheduling. A provider who offers to wash and seal the same day is either working on composite, which does not get sealed, or cutting a corner that will show.
Plants, Runoff, and Preparation
Deck cleaners are hard on landscaping, and decks usually sit right on top of a garden bed.
Plants below and beside the deck get pre-wetted, sometimes covered, and rinsed afterward. Anything directly under the deck deserves the most attention, because that is where runoff lands.
Household preparation is simple and makes a difference. Move furniture, grills, planters, and rugs off the deck. Close windows and doors on that side of the house. Say if there are lights, speakers, or an outlet built into the deck. Note any board you already know is soft.
If pets use the deck, plan for them to be inside during the work and until the surface has been rinsed and dried.
Timing and Sequence
Decks are cleaned in the working season, and they fit into a specific place in the exterior order.
Sequence. Gutters, then the house wash, then windows, then hardscape. A deck attached to the house is washed after siding pressure washing, because house-wash runoff lands on it. Free-standing decks are more flexible. The full order is in the exterior surface cleaning guide.
Season. Late spring is the usual choice: growth from the wet season is at its peak and there is a dry stretch ahead for sealing. Early autumn works too if the forecast allows a drying window.
Frequency. Once a year for most decks. Shaded decks under trees often want it annually with a mid-season rinse. Sealing runs on its own cycle, generally every two to three years depending on the product and exposure.
Decks are frequently booked with a patio and outdoor living clean, since the two usually share a space and a visit.
FAQ
Can a deck be pressure washed?
Only at low pressure with a wide fan tip held well back, and many professionals avoid pressure on wood entirely. High pressure erodes the soft wood between growth rings, leaving a furred surface that is permanent short of sanding. Chemistry with dwell time removes growth and greying far more safely.
How long after cleaning can a deck be sealed?
Usually two to three days of dry weather, and longer for dense hardwoods or in humid conditions. Wood must be dry through, not just dry on the surface, and a moisture meter is the reliable check. Sealing over damp wood causes clouding, poor adhesion, and early failure.
Is deck cleaning the same as deck restoration?
No. Cleaning removes growth, dirt, and surface greying. Restoration involves sanding, replacing damaged boards, tightening or repairing the structure, and applying a new finish. Cleaning is often the first step of restoration, but the two are quoted separately and the later stages are carpentry and finishing work.
How should composite decking be cleaned?
With a cleaner made for composite rather than a wood deck product, and according to the manufacturer's guidance. Many composite makers restrict certain chemicals and pressure levels, and using the wrong product can void a warranty. Mold in the embossed grain is the usual problem rather than greying.
What are the black streaks around the deck screws?
That is tannin bleed -- iron in corroding fasteners reacting with tannins in the wood. An oxalic acid brightener lifts the staining noticeably, but the streaks return as long as the fasteners keep corroding. Replacing them with stainless or coated fasteners is the lasting fix.
How often should a deck be cleaned?
Once a year suits most decks, timed for late spring when wet-season growth peaks. Decks in heavy shade or under trees often want an annual clean plus a mid-season rinse. Sealing runs on a separate cycle, generally every two to three years depending on the finish and exposure.
Deck results depend on the wood, the finish, and the condition, so a walk-through beats a phone estimate. Otesse is local, background-checks its crews, prices upfront with no hidden fees, and books online -- see home cleaning services or get a quote. Every property is different, so the real number depends on size, condition, and what you want covered.