Why Preparation Decides How Long the Finish Lasts

Most garden gates fail at the joints long before the timber itself gives up. Water sits in the end grain, frost gets into hairline cracks and a once-solid frame starts to swell and twist. A good coat of paint slows that process down, but only if it has something sound to cling to. Painting over flaking, greasy or damp timber is the single most common reason a gate needs repainting within a year.

So treat the paint as the final 20 per cent of the job. The sanding, filling and priming you do beforehand is what actually keeps the weather out.

Start With a Proper Look at the Gate

Before you reach for sandpaper, take the gate off its hinges if you can. It is far easier to work on a pair of trestles than to paint a swinging gate in a breeze, and you can check the frame for rot at the same time.

• Push a small screwdriver into the base of the stiles, the bottom rail and around any joints. Soft, spongy timber means rot, and paint will not fix it. Cut out the damaged section and splice in a new piece of matching timber, or accept that the gate is due for replacement.
• Check the mortise and tenon joints for movement. Loose joints should be cleaned out and re-glued with an exterior-grade wood adhesive, then clamped overnight.
• Look at the hardware. Rusty hinges, a stiff latch or a sagging gate will undo your work. A squirt of light oil and a tighten of the screws takes minutes now.
• Note the timber species. Softwood, oak, iroko and cedar all behave differently, and oak in particular needs handling with care.

Sanding, Filling and Dealing With Bare Timber

Wash the gate down first with warm water and a little sugar soap, then rinse and let it dry completely. This removes the algae, bird droppings and airborne grime that clog sandpaper and stop paint bonding.

Sand with the grain, starting at 80 grit if the surface is rough or has old flaking finish, then moving to 120 grit for a smooth key. On previously painted gates, feather the edges of any sound paint so you cannot feel a ridge with your fingertips. Remove all dust with a brush and a tack cloth.

Fill cracks, dents and old screw holes with an exterior-grade two-part wood filler. Do not use interior filler — it will shrink and crack after one wet winter.

Now the important bit for bare timber. Any knots need sealing with knotting solution, otherwise resin will bleed through and stain the topcoat. On oak, the natural tannins react with water-based paints and iron fixings, turning the finish a streaky black. Use a dedicated blocking primer on oak, and stainless steel or galvanised fixings throughout.

End grain soaks up paint like a sponge. Give every cut end, particularly the top and bottom of stiles and the underside of the bottom rail, an extra generous coat of primer. This is where rot usually begins.

Priming and Choosing an Exterior Coating

Bare timber needs a primer suited to the topcoat you intend to use. A solvent-borne wood primer is traditional and reliable; a water-based primer is quicker to dry and easier to clean up. Whichever you choose, apply it thinly and let it dry fully before sanding lightly.

For the topcoat, you have two sensible routes:

• Microporous exterior wood stain. It soaks into the timber and lets it breathe, so moisture can escape rather than becoming trapped. Ideal for softwood and for anyone who wants a natural look, and it is easy to top up every few years without stripping back.
• Exterior gloss or satin paint. Harder wearing and available in any colour, but it forms a film. Any water that gets behind it through a crack will lift the whole coat, so preparation and maintenance have to be thorough.

Whichever you pick, read the tin. Most exterior coatings need temperatures above 10°C, dry conditions and a few hours without rain. Humidity slows drying, and strong sunlight causes the paint to skin over while the timber beneath stays soft.

Applying the Finish and Keeping It Going

Stir the paint rather than shaking it, and apply with a brush slightly narrower than the gate rails so you can control the edges. Work in the direction of the grain, lay off lightly at the end of each stroke, and paint the gate in a logical order: top rail, stiles, bottom rail, then panels and any slats.

Two thin coats beat one thick one every time. Thick paint sags, traps solvent and dries unevenly. Allow the full drying time between coats, then a light sanding with 240 grit before the next coat.

Mask the hinges, latch and any glazing before you start, and wipe off drips immediately with a rag dampened in the appropriate thinners.

Once the gate is back on its hinges, check it in spring and autumn. Touch in any chips or worn patches straight away, and give the whole gate a fresh coat every two to three years for stain, or three to five for gloss. Ten minutes with a brush now saves a weekend of stripping later.