Somebody rang me last autumn about a deck at Culburra that had been painted with an exterior paint two summers earlier. It was peeling in sheets you could lift with a fingernail, and underneath it the timber was black. He wanted to know what paint to use this time.
The answer was none, and the reason had nothing to do with the brand.
The actual difference between the three
Oil soaks in. It sits inside the timber rather than on top of it, feeds the fibres, and when it wears out it fades away from the high-traffic areas rather than lifting. Nothing to strip, nothing to sand back. You clean it and put more on.
Stain is a middle case. There is pigment in it, which is what gives you the UV protection, and depending on the product it either penetrates like an oil or leaves a thin film. Penetrating stains behave like oil when they wear. Film-forming ones behave like paint.
Paint is a film. It sits on the surface and it is only as good as its grip on the board underneath. On a vertical wall that is fine. On a horizontal surface that gets walked on, rained on and heated to something like sixty degrees on a February afternoon, it is a hard ask.
Once you say it that way the Culburra deck explains itself. Water got under the film through the board ends and the gaps, could not get out, and pushed the paint off from behind. That is what peeling is. It is almost never the paint failing, it is water behind the paint doing what water does.
Why salt air changes the sums
Coastal exposure does two separate things and they get lumped together.
Sun is the bigger one. UV breaks down lignin in the timber surface, which is what turns an untreated deck that particular silver-grey. It also breaks down the coating on top of it, and a clear oil with no pigment has almost nothing stopping it. Which is why "clear" decking products need recoating so much more often than tinted ones — the pigment is the sunscreen.
Salt is the second. It builds up as a film, it holds moisture against the surface, and it accelerates corrosion of every fixing in the deck. On a deck a hundred metres from open water the nail heads and screw heads usually go before the boards do, and rust bleed staining out of a fixing is a decent early warning that the deck is getting more salt than you thought. Same mechanism we go through in the house washing post, applied to a horizontal surface that never gets rinsed by rain running off it.
Combined, they mean a deck facing north or west with nothing over it is on a considerably shorter cycle than the same deck on the shaded southern side of the house. Two decks on the same property can want different recoat intervals, which surprises people.
Recoat intervals, roughly
Nobody can give you a number that holds for every deck, and anyone who does is guessing. What I can give you is the shape of it.
Oil on an exposed coastal deck is annual, sometimes twice in the first year on new timber that is still drinking. Under a roof or on a shaded side, you might get eighteen months to two years. Tinted stain buys you longer than clear oil, call it two years exposed, and the wear is more even.
The test is not the calendar, it is water. Flick some onto the boards. If it beads, the coating is doing its job. If it soaks straight in and darkens the timber, the coating is gone and the deck has been unprotected for however long it took you to notice.
The mistake is waiting for it to look bad. A deck that has gone grey is not just cosmetically tired, it has been weathering unprotected, and the surface fibres have degraded to the point where the next coat has less to grab. Recoating on schedule is a wash-and-oil job. Recoating a grey deck means sanding first, which is most of the cost.
Getting the last coating off
The bad news for anyone with a painted or film-stained deck who wants to move to oil: it all has to come off. Oil cannot soak through a film. Half-stripped and re-oiled gives you a deck that is patchy where the old film survived and it will not weather evenly afterwards.
Sanding a deck is genuinely unpleasant work, the boards have to be re-fixed or punched first so the sander does not catch, and the dust from anything painted before the 1990s needs treating carefully because of lead. It is the main reason we push people towards oil the first time round. Choosing a film coating on a horizontal deck locks you into stripping it later, and that is a much bigger job than any recoat.
There is one exception worth naming. Decks that have been painted for a long time and still have a sound, well-adhered film are sometimes better left painted and maintained as painted. Not because it is the better system, but because the strip is not worth it. That is a judgement call made standing on the deck, and it is part of what we look at on deck and timber maintenance jobs.
Where coating stops mattering
Everything above assumes the deck underneath is sound. Check that first, because there is no coating that fixes a structural problem.
Push a screwdriver into the bearers and joists where they meet a post, and into the posts at ground level. If it goes in easily the timber has gone and coating the boards is money spent on something that needs rebuilding. Bounce in the middle of a span, boards that are cupping badly, a handrail with movement in it — all worth investigating before you spend a weekend sanding.
That kind of work is structural, and structural work on a deck is a licensed trade. A rebuild will almost certainly land over the $5,000 threshold in the Home Building Act, and NSW puts deck and pergola construction under structural landscaping work with its own licence category. The general building work rules set out the threshold itself.
We sand, coat, replace individual boards and sort out fixings where the frame under them is good. When it is not, we say so. If you are not sure which one you have, the screwdriver test at the posts answers it faster than anything else, and you can send us the photos.
Want a hand with this at your place? Get a free quote or call 0450 959 936.