A timber deck in Far North Queensland is asked to do something a deck in Melbourne is not. It takes intense UV for most of the year, then months of saturation and humidity, then heat again. Coatings that would last five or six years in a temperate climate can be visibly breaking down in two.
The tell is a deck that has gone blotchy rather than uniformly faded — dark in places, orange-brown in others, with pale scuffs through the traffic paths. That is not dirt. It is a coating that has worn through unevenly, and no amount of washing will fix it, because the problem is what is left of the finish rather than what is sitting on top.
What is actually happening
UV breaks the finish down from above. Ultraviolet degrades the binder in a coating. Once it goes, the surface starts to chalk and shed.
Moisture attacks from below and behind. Wet-season humidity moves through the timber. Where a coating is still intact it traps that moisture, which is why failing decks often lift and flake in patches rather than wearing evenly.
Traffic concentrates the wear. Steps, doorways and the path everyone walks take the finish off first. This is what produces the patchy look — different parts of the same deck are at genuinely different stages.
Salt accelerates all of it. Closer to the water — much of Port Douglas and Wonga Beach — salt exposure shortens the interval further.
Why washing and recoating does not work
The instinct is to clean it and put another coat on. The problem is that you are coating over a failed finish. The new coat bonds to the old one, and the old one is already letting go of the timber. It looks acceptable for a season and then lifts, usually worse than before, because now there is more material to fail.
If a deck is genuinely just dirty and the coating is sound, a clean and recoat is fine. If it is blotchy and wearing through, it is past that.
What restoration involves
Sanding back to bare timber. All of the old coating comes off, across the whole deck, until you are looking at raw wood. This is the step that determines whether the job lasts. A deck sanded properly comes back to an even, honey-coloured raw timber — the colour is often a surprise to owners who have only ever seen it coated.
Letting it dry. Bare timber needs to be dry before anything goes on it. Coating over damp wood traps moisture and guarantees early failure.
Two coats, not one. Whether the finish is a clear varnish or a pigmented stain, a single coat does not build enough film. Two good coats is the standard.
Clear finish or stain?
Worth understanding, because it changes the result dramatically:
- A clear varnish shows the raw sanded timber — light, warm, and honey-toned. It looks the most natural but offers less UV protection, so it needs recoating sooner.
- A pigmented stain goes on darker. The pigment blocks UV, so it lasts longer, but you lose some of the grain.
Neither is wrong. But it does mean two decks on the same property, finished differently, will not match — and a freshly stained deck will look considerably darker than a freshly varnished one.
How often
In this climate, plan on inspecting annually and expecting to recoat every two to three years for a clear finish, or three to four for a pigmented stain. Decks with heavy sun exposure or close to the water sit at the shorter end.
The mistake that costs money is waiting until the timber itself starts to grey and fibre up. At that point sanding removes more material, and badly weathered boards may need replacing.
Tony handles deck sanding and recoating as part of plastering and painting work. If your deck has gone blotchy, a look in person will tell you quickly whether it needs a full sand-back or just a clean and recoat.