Why spring is the right moment

Fence boards spend winter wet. Algae grows along shaded rails, the wood swells and greys, and any stain left from last year has thinned out on the sun-facing side. Staining in spring, once the frosts have passed and the wood has had a dry spell, gives you the best chance of an even finish. The boards are still cool, the sun isn't yet strong enough to bake a coat dry before you've brushed it out, and the fence has a full growing season to cure properly.

Aim for a stretch of dry weather with daytime temperatures between about 10°C and 25°C. Avoid a day of showers, and don't start if rain is forecast within 24 hours. If you're working on a fence that gets afternoon sun, stain the shaded side first and move round as the sun travels, rather than fighting a hot surface.

Choosing a water-based stain for a natural finish

For a natural look, choose a water-based stain rather than a paint or a heavy film-forming varnish. Stains soak into the timber and tint the grain, so the texture of the wood still reads through. Paints and thick varnishes sit on top, and on weathered boards they crack, peel and trap moisture underneath.

• Opacity matters. A clear or lightly tinted stain keeps the grain visible. A semi-transparent stain evens out colour without hiding it.
• Water-based is kinder to old wood. It's breathable, so any residual moisture in the boards can escape rather than blistering the finish.
• Drying times are short. You can often recoat in two to four hours, so the whole job can be done in a weekend.
• Clean-up is simple. Brushes and rollers rinse in warm soapy water, and there are no strong solvents in the air.

If you have a routered or rough-sawn board, expect a shade darker than the tin suggests. Always test on an offcut or a hidden end panel first.

Preparing weathered boards

Preparation is where a natural finish is won or lost. Grey, algae-covered boards will drink stain unevenly and end up patchy within a fortnight.

• Scrub the fence down with a stiff brush and warm water with a little mild detergent. Work along the grain, and pay attention to the bottom rails and any north-facing panels.
• Rinse thoroughly with a hose, then leave the fence to dry for at least 24 to 48 hours. Damp wood will reject the stain.
• To check, tape a square of clear plastic to a board and leave it for an hour. Condensation on the underside means it's still too wet.
• A light sand with 80 to 100 grit will open up the surface and smooth any raised grain. Don't over-sand old feather-edge boards — they're thinner than they look.
• Brush off dust, and mask or cover anything you don't want stained, including paths, gravel and neighbouring planting.

Thin coats and the back-brush

Two thin coats always beat one thick one. A heavy coat sits on the surface, dries unevenly and shows every lap mark. A thin coat sinks in, dries evenly and builds colour gradually.

Apply the first coat with a roller or a wide brush, working in sections no bigger than a panel or two. Then immediately back-brush the whole section with a brush, working with the grain. This is the step most people skip, and it's the one that prevents patchy colour. Back-brushing pushes the stain into the grain, evens out roller marks and floods the edges.

Pay close attention to edges and joints. On overlap and featheredge panels, work the brush into the lap where one board meets the next, so no bare strip appears when the wood moves. Do the same along the top and bottom rails, the post faces and the frame of any gate. End grain soaks up far more stain than the face, so brush it on sparingly — cut ends, post tops and the bottom of gate stiles will all go darker if you flood them.

Leave the first coat to dry as the tin directs, then apply a second thin coat the same way. Don't be tempted to top up a pale patch with a heavy dab; feather it out with the brush and let the second coat even things up.

Avoiding the usual mistakes

• Working in direct sun. The stain skins over before it soaks in, leaving streaks. Follow the shade round the garden.
• Staining a damp fence. Rain within a day or two of application can wash a water-based stain straight out of the grain.
• Forgetting gates and trellis. These take the most wear. Take gates off their hinges if you can, stain the top and bottom edges, and refit once dry.
• Starting at the wrong end. Work from one end of the run to the other so you always have a wet edge to blend into.

Keeping the natural look going

A stained fence will typically want a freshen-up every two to three years, depending on how much sun and rain it takes. Check each spring: if water beads on the surface, it's still protected. If it soaks straight in, it's time for another thin coat. A quick wash down and a single maintenance coat is far less work than stripping back a fence that's been left too long — and it keeps the timber looking like timber, which is the whole point of choosing a stain in the first place.