Staining near you

Dense hardwoods such as spotted gum, blackbutt, ironbark and jarrah are the mainstay of Australian decking and screening, and their density is exactly what makes coating them delicate. They absorb slowly, so a heavy first coat sits on the surface and stays sticky, and any excess has to be wiped back rather than left to dry. They are also high in tannin, which leaches with early rain and marks light-coloured render, painted walls, concrete and sandstone below the work.

Merbau and similar imported hardwoods are notorious for the same reason, and the usual practice is to wash the boards and allow the initial leaching to run off before coating, so the run-off does not end up on the paving. Whatever the species, the run-off has to be directed away from anything pale.

Treated pine and plantation softwood are the other half of the market. Freshly treated timber holds moisture from the treatment process and needs to dry before a coating will take, which is why a newly built deck is often left for a period before it is stained. When any treated timber is cut or sanded, the dust is the concern rather than the board, so cutting is done outdoors with dust controlled and offcuts are never burned.

The two enemies of a stain job are heat and moisture, and most of Australia offers one or the other for much of the year. In a hot northern summer a surface in direct sun can be far hotter than the air, and product applied to it flashes off before it can penetrate, leaving a patchy, gritty finish. The answer is to follow the shade around the building, start early, and stop when the surface is too hot to leave a hand on.

Moisture is the other constraint. Timber that has been rained on, hosed or pressure-cleaned holds water well below the surface, and a coating applied over it traps that water and either fails to adhere or goes cloudy. In the tropical and subtropical wet season the practical window narrows to a few consecutive dry days, and in a cool southern winter timber simply does not dry quickly enough for most products.

That makes autumn and spring the reliable seasons across most of the country, with an early start and a shaded sequence in summer. Dew is worth a mention too: a coating applied late in a southern afternoon can be hit by dew before it has cured, which leaves a milky bloom on the surface.

Staining is maintenance, not construction. A penetrating oil on a deck in full Australian sun will need attention within a year or two, sooner on the part that faces north or west and later in a shaded courtyard. The recoat is easy precisely because the product never formed a film: clean, let it dry, and apply again. Leaving it until the boards have gone grey turns an easy recoat into a full preparation job.

Film-forming and solid stains last longer but fail differently. When they go, they go by cracking and lifting at the edges, and the only honest repair is to strip back to sound timber over the affected area. That is why the interval between coats is not the whole story, and why the choice between an oil and a film product should reflect how willing you are to do frequent light work versus occasional heavy work.

Two habits extend any finish. Keep water off the timber where you can, which means clearing leaf litter from between boards, keeping pot plant saucers off the deck, and checking that a downpipe or an air conditioner condensate line is not discharging onto it. And wash the surface periodically, because mould and grime hold moisture against the coating and are the reason north-facing timber in the subtropics ages so much faster than the sheltered side.

Staining is the one finish that cannot hide what is under it. A coat of paint can be laid straight over sound existing paint; a stain has to reach bare timber, which means stripping, and on a house built before 1970 that is precisely the operation the authorities warn against. LeadSmart NSW's advice for paint in good condition is to leave it alone or paint over it — advice that a decision to stain deliberately sets aside. If you are set on it, the preparation has to be wet rather than dry, and on anything more than a small area it is worth asking honestly whether an opaque finish would do the job without turning the house into a work site.

Where preparation has to disturb old paint, LeadSmart NSW calls for an AS 1716-approved respirator or mask fitted with P1 or P2 filters and coveralls, an industrial or HEPA vacuum cleaner that is not used for day to day or household vacuuming, and waste sealed in heavy-duty plastic sheets or bags and disposed of at an approved part of the local waste facility. Dry sanding an old painted verandah rail on a windy day spreads that dust across a garden where children play, which is the reason this is professional work.

The other hazard is specific to oil-based finishes. Rags and cloths soaked in oil-based stain or oil can generate heat as the oil oxidises, and left crumpled in a bin or a bag in a hot shed they have started fires. Lay them out flat to dry in the open, or seal them in water in a metal container, before disposing of them.