The short answer
A Sydney timber deck needs a wash once or twice a year and are-oil every 9 to 18 months depending on exposure — full sun burns oil off fastest, while decks under tree canopy stay damp and grow mould instead. A grey, neglected deck can almost always be restored: wash, sand where the boards need it, two coats of oil. The line that matters is underneath — if the boards are the problem, it's a repair; if posts, bearers or joists have gone soft, it's a rebuild conversation, and no amount of oil changes that.
The maintenance schedule, by exposure
Exposure sets the cadence, not the calendar. Around the Lower North Shore the big divider is tree canopy: shaded decks keep their finish longer but never properly dry out, which trades an oiling problem for a mould one.
| Task | Full sun | Part shade | Under trees |
|---|---|---|---|
| Wash (deck cleaner, stiff broom) | Yearly | Yearly | Twice yearly — mould and leaf tannins build fast |
| Re-oil | Every 9–12 months | Every 12–18 months | When the water test says so — often 18 months, but only onto clean, dry timber |
| Fastener check | Yearly | Yearly | Yearly — damp accelerates corrosion, especially with salt air |
| Substructure inspection | Every 2 years | Every 2 years | Yearly — persistent damp is exactly what rots joists and posts |
Species adjust the schedule at the edges. Merbau bleeds tannins heavily in its first year — wash early and often, and keep the runoff away from pale pavers and render, because the stains outlast the embarrassment. Spotted gum and blackbutt are dense enough that the first coats of oil struggle to penetrate; expect a shorter first-year cadence — two lighter recoats — before they settle into the normal rhythm.
Oil, stain, or let it silver
Three legitimate choices, each with a trade the tin doesn't mention. Decking oilpenetrates the timber, feeds it, and shows the grain; it needs the most frequent recoating, but each recoat is a wash and an afternoon — no stripping, no drama. Film-forming stainsgo longer between coats and can even out mixed or patched timber, but they fail by peeling, and peeling only has one real fix: a full sand back to bare wood. Letting hardwood silver off is not neglect if it's chosen — dense species like spotted gum grey off gracefully — but the timber still needs washing, the fasteners still need checking, and unoiled boards check and splinter sooner. A silvered deck can be brought back to colour later; that's a restoration, not a loss.
Not sure which side of the wash-or-sand line your deck is on? Send photos and we'll tell you straight. See our deck repairs and restoration service or use the quote form below.
Restoring a grey deck: the sequence
Grey timber looks terminal and almost never is — the grey layer is millimetres deep. The sequence that brings it back is always the same three steps, with one honest decision in the middle:
- Wash. A proper deck cleaner or oxalic-acid brightener, a stiff broom, and restraint with the pressure washer — high pressure held close furs the timber and creates the sanding job you were trying to avoid.
- Sand — when it's needed. Sand if boards are cupped or furry, if an old film finish is peeling, or if the greying runs deep enough that oil would sit patchy. Skip it if the wash brings the timber back clean and sound; on a sound deck the wash alone does more than most owners expect.
- Oil. Two coats onto dry timber with a clear weather window. This is also the moment to punch down or replace proud fasteners and swap any split boards — oiling around problems just preserves them.
One safety note worth folding into any restoration: NSW building standards require a compliant balustrade wherever a deck sits 1m or more above the ground. Restoration is the natural moment to check rail heights and fixings — a balustrade that moves when leaned on is a today problem, not a someday one.
Repair, restore or rebuild — the decision logic
The whole decision comes down to one distinction: boards versus substructure. Boards, fasteners and finish are the deck's skin — all replaceable, all repair-level work. Posts, bearers and joists are its skeleton — if they've gone soft, you're in a rebuild conversation, because everything above them is standing on borrowed time. The frustrating part is that the skeleton is the part nobody looks at, which is why a proper inspection starts underneath, not on top.
| Symptom | What it usually means | Fix level |
|---|---|---|
| Grey, faded, water no longer beads | Finish is gone; timber likely fine underneath | Finish — wash and oil, sand if needed |
| Split, cupped or rotten individual boards | Localised board failure | Board — replace and colour-match |
| Rust streaks, proud or popped screw heads | Fastener corrosion — common in salt air | Fastener — replace with stainless or galvanised |
| Spongy spot underfoot | Rot in the board or, worse, the joist under it | Board if caught early; substructure if not |
| Deck moves or sways when walked | Post, bracing or ledger connection trouble | Substructure — inspect before anything else |
| Green film that keeps returning | Shade and trapped moisture, not a finish fault | Finish plus airflow — wash cadence, drainage, ventilation |
The warning signs worth acting on early: sponginess anywhere, movement when you walk the deck, rusted fasteners in rows (a sign the whole batch is going), and mould that comes straight back after cleaning under tree cover. Each of those is cheap to investigate and expensive to ignore — post rot caught early is a re-stump; caught late it's a new deck.
Every job we quote starts with the frame — footings, posts, bearers, joists, the house connection — before we talk about what's visible on top. If it's sound, you'll hear that too.Book a deck inspection and get the verdict in writing.
Why maintenance is the cheapest deck you'll ever own
A washed and oiled hardwood deck is a decades-long structure; a neglected one on a shaded Lower North Shore block can need serious work inside fifteen years. The difference is not the timber — it's whether water sits in the boards and fixings year after year. An afternoon's wash and a day's oiling, at the cadence in the table above, is the entire discipline. And if the deck you've inherited is already grey, spongy or moving, skip straight to an inspection: the answer is usually better than owners fear, and when it isn't, finding out early is what keeps a repair from becoming a rebuild. And if it does become a rebuild, read thedeck council approval guide before anyone orders timber.