How do you prep and paint a timber fence or deck?

A fence and a deck are not the same job

They look similar in the tin and behave nothing alike once they are down. A fence is a vertical surface that sheds water and gets walked past. A deck is a horizontal one that holds water in every gap, cops full sun all afternoon, and has people, chairs and dogs dragging across it.

That is why deck products publish foot traffic times and fence products do not, and why a deck that was oiled rather than painted takes far more work to change its mind about.

Cleaning comes before anything else

Sweep it, then wash it. Bunnings starts its deck guide with a broom and a scrape of any peeling flakes, then a deck cleaner scrubbed in and rinsed off with a hose or pressure washer, and it wants the timber completely dry afterwards. Cabot's asks for the same cleaner step and says to let the timber dry for at least an hour before coating.

Grey timber has to come off. That silvery surface layer is broken-down fibre, and paint stuck to it peels away carrying the fibre with it, which is the single most common reason a repainted deck fails in a season.

If the deck was previously oiled or stained, Cabot's gives a neat test: sprinkle water on it. If it beads up, there is still coating in the timber and it needs more sanding. If it soaks straight in, you are ready.

Does it need a primer?

Not always. Cabot's Timbercolour is self-priming on most surfaces, which is why it turns up on so many fence and deck jobs, but new timber is a different story. Cabot's sells a timber prep to scrub into damp new boards to draw out tannins and oils, and says using it removes the usual four to six week wait for new timber to weather before coating.

Unpainted timber also needs an extra coat: three rather than two, by Cabot's own instructions. Some colours need another one again for full opacity.

Coats, times, and when you can walk on it

The figures below come off the Cabot's Timbercolour sheet, and they are the ones worth writing on the back of your hand before you start. Miss the foot traffic times and the first person across the deck will leave a print you cannot sand out without starting again.

• Spread rate: 16 square metres a litre.
• Touch dry: 30 minutes. Recoat: 2 hours.
• Two generous coats on most surfaces, three on unpainted timber.
• Light foot traffic: 24 hours after the last coat.
• Normal foot traffic: 72 hours. Furniture and rugs back: 7 days.
• Above 10 degrees during application and drying, and not with rain coming.

Painting a fence without painting the garden

Bunnings suggests looking for a window of two or three warm, sunny days in a row, which on the Peninsula usually means late spring or early autumn rather than the middle of summer. Our guide on when to paint outside around Melbourne goes into the weather side of it.

Work in small sections. The Bunnings fence method is three or four pickets at a time: cut in the edges with a brush, then roll the flat faces while that edge is still wet, and keep moving along. It sounds slow and it is much faster than fixing the lap marks you get from doing all the edges first.

Drop sheets along the base save the lawn and the garden bed, and seal the end grain on every cut and post top. End grain drinks water and is where fence palings start to rot. If you are thinking of spraying, think about the neighbour's car and the next-door washing first: overspray travels a long way in the lightest breeze.

Should a deck be painted at all?

This is worth deciding before you buy anything, because it is a one-way door. Bunnings is direct about it: if your deck is currently stained, you have to sand the whole thing back to bare timber before painting, with an 80 grit belt, or the paint will not hold.

Paint gives a solid colour, hides mismatched boards and covers a deck that has seen better days. It also wears at the traffic lines, in front of the door and at the steps, and touching it up means matching a colour that has been in the sun for two summers. Oils and stains fade rather than peel, and recoat without stripping, but they will not hide anything.

Neither answer is wrong. Just pick with your eyes open, because going from paint back to oil means sanding the lot.

When is it worth getting someone in?

A single fence line or a small deck on a dry weekend is well within reach of anyone comfortable with a brush and a sander, and doing it yourself is a low-cost way to add years to timber you already own. There are a few points where handing it over makes more sense.

• A large deck that has to go back to bare timber. Belt sanding a deck is a hire-gear job that fills the yard with dust and takes most of a weekend before a drop of paint goes on.
• Long fence runs where spraying is the only sensible method. We brush and roll fences and decks rather than spray, so for those we'll tell you to find a spray specialist.
• Rotten palings, soft posts or bouncy deck boards. That is carpentry, and painting over it just hides it for a season.
• Balustrades, raised decks and anything where you are working off a ladder on sloping ground.
• Timber you cannot identify, especially older hardwood that bleeds tannin through a light colour.

If it is part of a bigger outside job

Fences and decks often come up while we are looking at the house, and it is worth asking about them when we quote an exterior repaint rather than doing them separately six months later. If the house itself is next on your list, our guide on which paint suits weatherboards near the coast covers what goes on the walls.

Quick questions

Sources

What this guide relies on. Product advice changes, so check the maker's current instructions for the exact paint you're using.

1. Timbercolour Deck and Exterior Paint: coats, drying and foot traffic — Cabot's
2. How to paint your deck with Timbercolour — Cabot's
3. How to paint a deck — Bunnings Warehouse
4. How to add some colour to your timber picket fence — Bunnings Warehouse