Firewood: What to Burn, and How Dry It Has to Be

Almost every complaint about a smoky fire, a fire that will not catch, or a fire pit that “does not work as advertised” comes down to one number: how much water is still in the wood.

Species matters, but far less than people think. A seasoned softwood will out-burn an unseasoned oak every single time, because before wood can burn, the fire has to boil off the water inside it — and that energy comes out of the heat you wanted.

Why moisture beats species

Freshly cut wood can be half water by weight. Every drop of it has to be turned to steam before the wood itself will burn, and that energy is subtracted from the fire.

That is the whole explanation for the familiar symptoms of wet wood: it hisses, it steams from the cut ends, it smoulders instead of flaming, it needs constant relighting, and it smokes heavily — because the fire never gets hot enough to burn its own smoke. On a smokeless fire pit it also defeats the entire mechanism, since the secondary burn depends on reaching a high temperature.

Below about 20 percent moisture, wood lights easily, burns hot, and produces comparatively little smoke. Above roughly 25 percent, you are mostly making steam.

Species, honestly ranked

Heat output tracks density almost exactly: a denser log contains more wood and less air, so it holds more energy. The trade-off is that dense woods are harder to light and slower to season.

Seasoning: split, stack, cover the top

Wood dries almost entirely through its cut end grain, not its sides. Bark is the tree’s own waterproofing, which is why a whole unsplit round can sit for three years and still be wet inside.

Split it first. This is the step that does most of the work, and it should happen at the start of the seasoning period, not the end.

Stack it off the ground on pallets or rails, in single rows if you can, with gaps for air.

Cover the top only. A tarp over the whole pile traps moisture and keeps the wood wet — the sides need to breathe. Cover the top third and leave the flanks open.

Give it sun and wind. A sunny, exposed spot dries wood far faster than a sheltered corner.

Then wait. Six months for ash and birch, a year for most, two for oak.

What never to burn

This list is about what comes out of the fire and into the air you are sitting in.

Pressure-treated, painted, stained, or glued wood. Old decking, fence posts, pallets, plywood, MDF, chipboard. The preservatives, paints and adhesives do not disappear in a fire; they go into the smoke and into the ash.

Driftwood. Sea salt releases corrosive compounds when burned.

Poison ivy, poison oak, poison sumac. The oil that causes the rash becomes airborne in the smoke and inhaling it can cause a severe reaction in the lungs. This is the most dangerous item on the list and the one people do not expect.

Large amounts of green or rotten wood. Rotten wood has lost most of its energy content and mostly smoulders.

Anything you cannot identify. If you do not know what it was treated with, do not burn it.

Buying it without being caught out

A full cord is a precisely defined stack: 4 ft high × 4 ft deep × 8 ft long, or 128 cubic feet.

A face cord or rick is 4 ft × 8 ft but only one log deep — so if the logs are 16 inches, it is a third of a full cord. This is the most common way to end up paying cord money for a fraction of a cord, and the terms are used loosely.

Ask three questions: what species, how long since it was split, and is that a full cord or a face cord. Then check the ends of the logs when it arrives — if there are no cracks and the wood is still tan rather than grey, it was not seasoned, whatever you were told, and you are buying next winter’s wood rather than this winter’s.