Three finishes, and the maintenance each one signs you up for.

Nothing at all

Leave white oak, locust or cedar bare and it turns silver-grey over about eighteen months, evenly, and then stops. It is not decay. The grey layer is a few cells thick and the wood underneath is unchanged, which is what a barn board is.

Costs nothing, asks nothing, and it is what I would do with a bench that lives at the bottom of a garden. The only real objection is that people expect furniture to look new, and this stops looking new almost immediately.

• Yearly work: none.
• Best on: benches, planters, anything under a tree.
• Added cost: nothing.

Penetrating oil

A hard-wax or tung oil soaks in rather than sitting on top, so it keeps the wood the colour it is when you first see it planed. It also cannot peel, because there is no film to peel. That single property is why it is the finish on almost everything that leaves here.

The trade is that it wears. Once a year, in spring, you wipe the piece down and put another coat on with a rag, and it takes about twenty minutes for a table. If you skip two years nothing terrible happens; it just starts going grey, and you can either let it or sand it back.

• Yearly work: one coat, spring, twenty minutes.
• Best on: dining tables and anything you will look at closely.
• Added cost: $120 on a six foot table, and a tin comes with it.

Paint

A real exterior paint over a real primer lasts six to eight years on outdoor furniture and is the right answer on Douglas fir, which has nothing worth looking at underneath. It is also the only finish that will genuinely stop UV, which matters if the piece sits in full south sun all day.

The catch is the ending. When paint finally fails it fails by lifting, and getting it off a chair with turned parts is a weekend nobody enjoys. Paint flat things.

• Yearly work: none for years, then a real job.
• Best on: pergolas, arbours, fir, anything already destined for a colour.
• Added cost: $200 and up, depending on the shape.

The one I will not do

Polyurethane forms a film. Wood outdoors moves with every wet week and every dry one, and eventually the film cracks somewhere you cannot see, usually along an edge. Water goes in through the crack and then cannot get out, because the rest of the film is still doing its job. So the wood underneath stays wet while the surface looks perfect, and by the time a black stain appears there is rot under it.

Then the repair is not a coat of anything, it is stripping the whole piece and starting again. An oiled table with the same neglect just goes grey and sands back in an afternoon. That is the whole argument, and it is why every piece that goes out of here is finished with something that fails gracefully.

Two things to do whatever you choose

• Get it off the ground. Feet, pads, or a gravel bed. Ninety percent of outdoor furniture that rots, rots from the bottom of the leg upward, because the end grain is a straw sitting in a puddle.
• Do not cover it in plastic all winter. A tarp holds moisture against the wood and turns a dry cold season into a wet warm one. Either bring it in or leave it out. The middle option is the only one that does damage.

Coming back for a refinish

Any piece I built comes back to the bench for a sand and re-oil at cost of materials plus half a day, whenever you want it, for as long as you own it. About four pieces a year come back and every one of them goes home looking like the week it was made.