Paint or stain a deck? The trade-off nobody explains

For the flat boards you walk on, use a penetrating stain or oil rather than paint. Paint holds colour longer and hides ugly timber, but on a horizontal surface it eventually fails as a peeling film, and taking a failed film off a deck is a far worse job than recoating a stain that has simply worn thin.

The exception is everything you do not walk on. Handrails, balustrades, posts and fascias are vertical, they shed water, and paint on those is usually the better answer.

Why does paint fail on a deck when it lasts fine on a wall?

A wall is vertical, so water runs off it in seconds. A deck holds water in every groove and every joint, takes direct summer sun with nothing shading it, gets walked on, has furniture dragged across it, and moves constantly as the timber takes up and gives off moisture.

Paint is a film sitting on top of the timber. Once water gets under that film through a check in the grain, a cut end or a screw hole, the film lifts, and it lifts in sheets. Resene's technical advice on deck coatings is blunt about the mechanism: where boards have checking or grain cracks, moisture will eventually get in and the paint coatings will lift and peel.

A penetrating oil or stain does not form a film. It soaks into the grain and wears from the surface down, so a tired stain looks faded and patchy rather than flaky. That single difference decides how much work your next recoat is.

What is the actual difference between the three options?

Coating	How it sits	Typical recoat	How it fails	Prep for the next coat
Penetrating oil or stain	Soaks into the grain, leaves no film	One coat every two to three summers	Fades and goes patchy	Wash, treat moss and mould, dry, recoat
Film-forming stain	Thin film on the surface	Longer between coats than an oil	Peels at board edges and joints	Old film must come off before anything else goes on
Deck paint with grit	Full film	Longest colour life of the three	Peels in sheets once water gets underneath	Sand or strip back, which is the expensive weekend

Resene put penetrating stains at one coat every two summers, or every three on a lightly used deck. Paint outlasts that on colour, which is the whole appeal of it. The catch is entirely in the last column.

Is a painted deck slippery?

Yes, unless you choose against it. A smooth film with any sheen in it is slick the moment it is wet, and Resene's advice on walked-on surfaces is that a glossier paint is not recommended, because it becomes slippery and a hazard when wet. If you do paint a deck, use a product with grit already in it, or add an anti-slip additive to the topcoat.

A penetrating stain leaves the timber texture exposed, so grip is built in. On a wet winter morning that is not a small point, and it matters most on steps.

Does the timber change the answer?

H3.2 treated pine is the standard deck here. New pine wants four to six months of weathering before its first coat if you can wait, so the surface will actually take a stain. If you cannot wait, scrub it with a timber and deck wash first to open the grain. Skipping that step is the most common reason a first coat sits on the surface and wears off within a season.

Kwila and other dense hardwoods leach tannin for the first few months. Expect brown run-off onto concrete and paving, and expect the red to silver off over time. A natural oil holds that silvered look. A tinted hardwood stain puts the red back.

Macrocarpa and other locally milled boards are almost always left to a natural oil, because painting them defeats the reason anyone chose them.

What does Wellington weather do to a deck?

Two different problems, depending on where the deck sits. A north or west facing deck takes serious sun all summer, so coatings there fade fast and the recoat interval sits at the short end of the range. A south facing or shaded deck barely dries between June and September, so the enemy is moss, lichen and slime rather than sun. That deck needs a moss and mould treatment and a proper scrub before anything else, and it needs the surrounding planting cut back so air can reach it.

Timing matters more here than in most of the country. A deck coating wants dry timber and a run of dry days, which in practice means late spring through to March. Doing it in July across two fine days between fronts wastes the product, because the boards are still carrying moisture even when the surface looks dry.

Should you strip an old painted deck back?

Only if it is genuinely failing. A painted deck with sound, well-adhered paint can be washed, sanded where it is dull, and recoated with more of the same, and that is by far the cheapest path forward. Switching a painted deck to a penetrating oil is the expensive direction, because oil cannot penetrate anything until every trace of the old film is gone.

If the paint is already peeling in sheets, you are stripping it whatever you choose next. At that point it is worth deciding what you actually want for the following ten years rather than defaulting back to paint because paint is what was there.

When should you not spend anything?

Silvered timber is not damaged timber. Pine and hardwood both go grey on the surface long before there is anything structurally wrong, and if you like the grey, leaving a deck uncoated is a legitimate choice. It will weather faster and check more. It will not fall down.

Do not coat a deck you have not checked underneath. Push a screwdriver into the joists near the bearers and around the fixings. Soft timber, rusting brackets or a loose handrail are jobs that come before any coating, and a fresh coat over rot only hides the date.

This is also a genuine do-it-yourself job. Washing, scrubbing and rolling an oil onto a deck takes a weekend and no particular skill. Where it is worth paying someone is the painted work around it, the balustrades, stair stringers and the fascia tying back into the house, which normally belongs with an exterior repaint rather than a deck job.

What we would do on a typical Wellington deck

• Boards: penetrating oil or stain, recoated every second summer, washed every spring.
• Handrails, posts and balustrade: paint, because they are vertical, they shed water and they are what people look at.
• Stair treads: whatever the boards get, and never a gloss.
• Fascia and any timber tying into the house: match the house, not the deck.
• Underside of a raised deck: leave it unless it is in full view. Coating it adds real cost and does very little.

If you want the timber on your place assessed properly, our wood staining work covers decks, fences and exterior timber. Get in touch and we will tell you honestly whether it needs a coating or just a wash.