Timber benchtops, chopping boards and borer

A timber benchtop or a good wooden chopping board is one of the pleasures of a kitchen. It is warm to touch, kind to knives and ages well if you look after it. It is also the one surface in the kitchen that asks for a little regular care, because wood moves with water and needs a finish to keep it out.

How timber benchtops are finished

Consumer NZ’s benchtop guide describes timber and bamboo benchtops as planks or strips glued together, needing to be oiled or waxed regularly or given a polyurethane resin finish. Those are the two families you will meet:

• Oiled or waxed. The oil soaks into the wood and hardens, leaving a natural, slightly matt surface. It is easy to repair, because you can sand a damaged patch and re-oil just that spot. The trade-off is upkeep.
• Lacquered or polyurethane. A hard film sits on top of the wood. It needs much less upkeep and resists water well, but once it is scratched through or worn at the sink, repairs mean sanding back and refinishing a whole section.

Check what your benchtop has before you do anything. If water beads up on a glossy film, it is probably lacquered; leave it alone and clean it with a damp cloth and mild detergent. If the surface feels like bare, smooth wood, it is oiled.

Oiling and re-oiling

For an oiled benchtop, use the oil the maker recommends, or a food-safe finishing oil sold for benchtops and boards. Then:

1. Clean the surface and let it dry completely.
2. Apply a thin coat with a lint-free cloth, working along the grain.
3. Leave it to soak in for the time on the tin, usually fifteen minutes to an hour.
4. Wipe off every bit of excess. Oil left sitting on the surface goes sticky.
5. Let it harden overnight before heavy use.

A new oiled benchtop wants several coats in its first few weeks. After that, re-oil whenever water stops beading on the surface and starts soaking in, which for most kitchens means every few months, and more often around the sink and the kettle.

Oily rags can heat up and catch fire on their own as the oil hardens. Lay them flat outside to dry, or soak them in water in a sealed container, before throwing them away. Do not leave them balled up in a bin.

Water rings, stains and dark marks

• White rings usually mean moisture trapped in the finish rather than in the wood. On oiled timber, a light rub with fine abrasive pad and a fresh coat of oil often lifts them.
• Dark grey or black marks around the sink or under a dish rack mean water has got into the wood itself. Light marks can sometimes be sanded out. Deep ones are permanent.
• Lifting or swelling edges around the sink or dishwasher mean water is getting under the finish or into the end grain. That spot needs sealing properly, or the damage spreads.

The best prevention is boring: wipe up water, do not stand wet dish racks directly on the timber, and use a trivet for hot pans.

Chopping boards

Wooden boards need the same care in miniature.

• Wash them by hand in hot soapy water, rinse, and dry standing on edge so air reaches both sides. Do not soak them, and do not put them in the dishwasher, which splits and warps them.
• Oil them with a food-safe oil when they look dry and pale.
• Keep a separate board for raw meat, chicken and fish, and wash it straight after use. Many cooks use a plastic board for raw meat because it can go in the dishwasher.
• Retire a board with deep cracks or grooves you cannot scrub clean.

Damp corners and borer

Kitchens are full of the places wood stays damp: under the sink, behind the dishwasher, at the back of a cupboard against an outside wall, around a leaking tap. Damp timber swells, stains and eventually rots. It is also where people often first notice borer.

The common house borer in New Zealand is Anobium punctatum, a small beetle originally from Europe. As the summary on Wikipedia explains, its larvae bore through timber for several years, feeding on the starchy sapwood of seasoned timber rather than live or freshly cut wood. When the adults are ready, they chew out through the surface, leaving round exit holes about 1 to 1.5 mm across and spilling fine dust, called frass. Those holes and that dust are usually the first sign anyone sees.

What to look for in and around a kitchen:

• Small round holes in unfinished timber, such as the backs of cupboards, the underside of shelves, exposed framing under the sink, or old furniture.
• Little piles of pale, gritty powder under those holes or on the floor beneath. Fresh, light-coloured frass suggests recent activity.
• Old pine and other sapwood-heavy timbers, which are more likely to be affected than hardwoods. A painted or sealed benchtop surface is rarely the problem; the unfinished timber behind and underneath it is where to look.

When to get a timber check

A few old holes in a piece of furniture you have had for decades are not an emergency. Get a qualified building inspector or a borer treatment specialist to look when:

• you see fresh frass or new holes appearing,
• holes appear in structural timber, such as floor joists, framing or the subfloor,
• timber feels soft or crumbly when you press it with a screwdriver,
• or you are buying an older house, where a pre-purchase inspection should cover borer and rot.

Fix the damp first, wherever it is. Dry, well-ventilated timber is far less inviting, and a leaking tap fixed today saves a cupboard replaced later.