Why Preparation Decides How Long the Finish Lasts

A wooden gate lives a hard life. It takes horizontal rain on one side, sun on the other, and a good deal of knocking about from hinges, latches and bin lorries. Paint is the thin shield standing between that timber and the weather, and the simple truth is that no paint — however expensive — will hold up on a badly prepared surface.

The most common reason a gate coating fails within a year or two is not the product. It is skipping sanding, painting over dirt, or slapping on thick, hasty coats that blister in the first cold snap. Treat preparation as two-thirds of the job and you will get a finish that looks smart and lasts several seasons before it needs so much as a touch-up.

• Sand the timber smooth and dust-free
• Clean off grime, algae and old flaking finishes
• Prime bare wood, especially knots and end grain
• Apply thin coats of a proper exterior wood paint

Start With a Clean, Sound Surface

Give the gate a proper wash before you touch it with abrasive paper, otherwise you will simply rub grit and algae into the grain. Warm water with a little detergent and a stiff brush handles most of it — a domestic sugar soap solution is ideal. Green algae and lichen are common on the shaded side of a gate, and they need removing completely rather than painting over. A dedicated mould and algae cleaner, used as directed and rinsed thoroughly, will lift it.

Once the gate is dry, scrape back any areas where the old coating has failed. Paint that is flaking or blistering is a sign that moisture has got underneath, so it has all got to come off. Sound, well-bonded paint can simply be sanded to give a key. If you find soft, spongy timber with a screwdriver tip, rot has taken hold: cut it out, treat the surrounding wood with a preservative and repair with a two-part exterior wood filler before you go any further.

Sanding, Filling and Repairs

Sanding is about two things: knocking back any previous coating to a dull, keyed surface, and smoothing bare timber so the paint sits flat. Start with a medium grit around 80 to 120, work with the grain, and finish with 120 to 180 for a good surface. An orbital sander makes quick work of flat rails and ledges, but the stiles, edges and mouldings are usually better done by hand with a sanding block.

While you have the gate bare, check the hardware and the structure. Tighten or replace screws, and deal with any swollen edge that scrapes against the post. If a gate has swollen shut, plane a millimetre or two off the leading edge now — painting it first and discovering it sticks afterwards is a miserable afternoon's work. Fill small cracks, nail holes and open joints with an exterior-grade filler, then sand flush once hardened.

Priming Bare Timber Properly

Bare wood is thirsty, and paint applied straight onto it will be starved of binder and dry patchy. Prime everything that is bare, but pay particular attention to three places: knots, end grain and any cut edges.

• Knots: resinous timber such as pine bleeds sticky sap through water-based coatings. Seal knots with a knotting solution or a shellac-based primer before priming the panel.
• End grain: the top of the gate and the bottom of the stiles soak up moisture like a bundle of drinking straws. Give these areas an extra coat, thinned slightly so it soaks in.
• Bottom rail: this is where most gates rot first. It needs the best protection you can give it, including the underside.

New or stripped gates are best painted on all faces, including the top and bottom edges, before hanging — either lying flat on trestles or with the gate taken off its hinges. It is far easier to reach every surface properly this way, and you avoid the classic mistake of painting only the side the neighbours see.

Choosing the Right Exterior Paint

Use a product made for exterior woodwork. Interior emulsion or trim paint will chalk, crack and flake within months outdoors. You have broadly three options:

• Water-based exterior wood paint: quick drying, low odour, easy to clean up, and it stays flexible. It is the sensible modern choice for most gates.
• Solvent-based exterior gloss or satin: a harder, glossier finish with excellent water resistance, but slower to dry, stronger smelling, and it can become brittle on timber that moves a lot.
• Wood stain or opaque preserver: a good middle ground if you want to see the grain, though it offers less build and needs refreshing more often.

Whatever you pick, stir it thoroughly rather than shaking the tin, and decant what you need into a smaller container so the main tin stays clean. A quality 50mm synthetic brush for water-based paint, or a natural-bristle brush for solvent-based, plus a small brush for mouldings, is all the kit you need.

Thin Coats, Patient Application

Now for the part most people rush. Apply thin coats and build the finish up, rather than trying to cover everything in one go. Thick paint skins over on the surface while staying soft underneath, and that is exactly what blisters and peels later.

Work in the shade where you can, on a dry day between roughly 10°C and 25°C, and never paint damp timber or when rain is due within the drying time. A gate in full sun will dry too fast, leaving brush marks and lap lines. Brush with the grain, lay off lightly at the end of each section, and watch the places where drips collect: the bottom rail, the joints where stiles meet rails, and the underside of the top edge.

Follow the manufacturer's drying times, and lightly sand between coats with a fine paper to remove nibs and give the next coat a key. Two topcoats over a primer is the usual minimum; three on the bottom rail and any exposed end grain will pay you back. Once the gate is thoroughly dry, refit or close it — but check the hinges and latch are clear of the fresh paint before you swing it shut.