The single number that determines whether your fire lights easily and burns clean, or smoulders and smokes.
Last updated August 2026 · William Alexander Logs
Moisture content is the percentage of a log's weight that is water, measured against its dry weight. A freshly felled tree can be well over 50% moisture. Properly dried firewood, whether seasoned naturally or kiln-dried, needs to be brought down to 20% or below before it is genuinely good to burn.
Below roughly 20% moisture, a fire lights easily and the wood's own energy goes almost entirely into producing heat. Above that threshold, an increasing share of the fire's energy is spent boiling off water inside the log before it can burn properly, which is why wet or unseasoned wood is slow to catch, produces more smoke, and burns at a noticeably lower temperature. It is also the exact threshold behind the Woodsure Ready to Burn certification and the UK's Smoke Control Area rules.
A wet fire smoulders rather than burns cleanly, produces visibly more smoke, and deposits far more tar and creosote inside a chimney or flue over time, which is a genuine chimney fire risk if it builds up. It also means you burn through more logs for less heat, since a good share of each log's energy goes into evaporating water rather than warming the room.
The standard tool is a firewood moisture meter, which reads the electrical resistance between two probes pushed into a freshly split face of a log (moisture on the outer surface alone can give a misleading reading, which is why the reading is taken on a freshly split face). Certified suppliers such as ourselves test batches regularly as part of the Woodsure Ready to Burn audit process, rather than relying on a one-off check.
Our kiln-drying process is designed to bring every batch below 20% moisture reliably, rather than hoping a stack has sat long enough in a shed. That consistency is exactly what the Woodsure Ready to Burn certification (WS721) independently checks, which is why we display it rather than just claiming "dry logs".
The UK's official certification for firewood that is genuinely dry enough to burn safely, cleanly and legally, and how to check it for yourself.
Read the guide →Both can burn well. The difference is how the moisture is removed, and whether you can trust it before you strike a match.
Read the guide →Kiln-dried logs arrive ready to burn. Storing them well is what keeps them that way until you need them.
Read the guide →Kiln-dried, Woodsure Ready to Burn certified firewood and peat-free compost, delivered on the day you choose.