What firewood to burn: oak, holm oak, pine and other woods compared

When we inspect a flue with a lot of creosote built up in a short time, one of the first questions we ask is what firewood has been burnt. There is almost always a pattern: cheap wood bought in small bags at a petrol station or supermarket, of mixed origin and with no real guarantee of being dry. Not all wood performs the same, nor leaves the same residue, and the difference shows both in your pocket and in how often you have to call us.

Hardwoods: the ones that really heat a house

Holm oak, oak, beech and ash are the reference woods for daily use in winter. They are dense, burn slowly, give a long, steady bed of embers, and produce considerably less creosote than softwoods for the same number of hours of use. The trade-off is the drying time: between 18 and 24 months split and stacked in the open, not the 3-4 months sometimes promised by whoever sells it freshly cut.

Softwoods: good for getting started, not for the whole winter

Pine, fir and poplar catch in minutes and are very handy for getting the fire going, but their high resin content means they burn fast and give off more smoke — and more creosote — if they are not completely dry. In mountain areas where pine is the most accessible firewood, what we usually recommend is using it to start the fire (see our top-down method) and keeping holm oak or oak to maintain the embers.

What you should never put on the fire

• Painted, varnished or treated wood: old furniture, industrial pallets, building offcuts. When it burns it releases compounds you do not want to be breathing in your living room.
• Wood from removals or packaging: it often has staples, nails or industrial adhesives in it.
• Green, freshly cut wood: at over 40-50% moisture it barely burns and produces a disproportionate amount of smoke and creosote.

At a glance

• Holm oak / oak: slow burning, plenty of heat, few sparks — the best for daily use if you can afford it.
• Beech / ash: a good middle ground between heat and ease of lighting.
• Pine / fir: quick to start, burns fast, more resin — ideal as kindling wood, not as the only firewood of the season.
• Poplar / willow: low heat output and very fast burning — the least cost-effective option in the long run.

How to store it so it reaches winter dry

Stack it under cover but with the sides open so the air can circulate, on pallets or supports that keep it off the ground, and leave it like that for at least a year, better two. A firewood moisture meter costs little and saves a lot of surprises: below 20% moisture, the wood is ready to burn.

Frequently asked questions