Good firewood for a wood-fired hot tub is not defined by species alone. The log must suit the firebox, be dry enough to burn cleanly and be stored where air can move around it while rain is kept off. A well-organised supply makes damp batches obvious and reduces avoidable smoke, soot and disappointing heat output.
Dry fuel is an operating condition, not a cosmetic preference
Water inside a log consumes part of the fire’s energy as it evaporates. The combustion chamber struggles to reach a stable temperature, smoke and deposits can increase, and less useful heat reaches the tub water. It is then easy to blame the heater size when the actual problem is wet fuel, poor airflow or both.
Dry does not mean “anything made of wood”. Painted, stained, glued or chemically treated timber is not suitable unless an appliance is explicitly designed and authorised for it. Old furniture, MDF and uncertain pallets can contain coatings, resin, nails and contamination. Burn only the fuel permitted by the heater manufacturer and check local smoke and nuisance requirements.
Choose a store that sheds rain and admits air
A useful store combines four things: a roof, ventilation at the sides, separation from damp ground and a safe distance from ignition sources. A back wall is acceptable if an air gap prevents the stack remaining wet against cold masonry. Drainage beneath the store matters; a perfect roof does little for logs sitting over a puddle.
Raise the stack on a durable open base. Protect the top and the main weather side, but avoid a plastic sheet wrapped around every face. It may keep direct rain out while trapping condensation and slowing drying. Keep the store away from the stove, flue, sparks and the access route used to load the fire.
| Storage detail | Useful arrangement | Problem arrangement |
|---|---|---|
| Base | Stable, drained and raised | Soil, lawn or standing water |
| Rain protection | Roof or top cover with an overhang | Stack sealed inside plastic |
| Air movement | Open sides and a gap behind | Unventilated box or cellar |
| Stock control | Oldest dry batch used first | Fresh and seasoned logs mixed together |
Split and stack to suit the actual heater
Split logs generally dry more evenly than large round pieces. Their final length and cross-section must suit the firebox and the permitted fuel load. Logs that are too long tempt the user to leave the door insecure; oversized loads restrict air and can overfire parts of the system. Very small, extremely dry pieces can burn rapidly. Use the appliance instructions rather than copying the log size used in a house stove.
Build a stable stack without packing it solid. Crossed ends can stabilise a free-standing row, but high stacks need restraint and should not be within a child’s play area. Keep deliveries separate until their condition is known. A simple date marker on the rack makes stock rotation much easier.
Measure moisture on a freshly split face
A handheld meter is useful only when used consistently. Select logs from different levels and parts of the stack. Split a representative piece and test the newly exposed inner face in the orientation stated by the meter instructions. A reading taken only from a dry end can miss a wetter core.
Allow for the meter’s stated accuracy, wood setting and temperature limitations. One number does not certify an entire delivery. The official Ready to Burn scheme in England uses 20% moisture or less for certified small-volume firewood. Scotland, Wales and Northern Ireland have their own rules and local smoke controls, so this article should not be treated as a substitute for checking the location and appliance.
Drying time is a result, not a reliable calendar promise
There is no universal number of months. Species, starting moisture, log size, when it was split, airflow, rainfall and store position all affect the result. “Seasoned for two summers” proves little if unsplit rounds sat on wet soil. Conversely, well-split timber in an exposed, covered rack may dry more effectively.
Use the purchase date, storage conditions and repeated measurements together. If wood sold as dry is unexpectedly wet, keep that delivery separate while you discuss it with the supplier. A mixed stack is much harder to assess or resolve.
Keep only a small day supply beside the tub
Move only the expected quantity to the heater area. Keep it dry, stable and outside every clearance specified for the stove and flue. Never put logs on the heater, lean them against the chimney or try to dry them at the firebox door. Hot surfaces and sparks make this an avoidable fire risk.
Actual consumption depends on water volume, starting temperature, weather, cover condition, fuel quality and useful heater output. The article on wood-fired hot-tub running costs explains how to compare those variables without promising a universal number of logs.
Separate wet, dirty or contaminated wood
Brush off dry loose dirt before storage. Do not burn heavily mouldy, oil-contaminated, painted or treated wood. Small insect holes do not automatically make a log unusable, but infested firewood should not be stored inside the home and local pest guidance should be followed.
If one part of the stack becomes soaked, separate those logs and correct the roof, base or ventilation before rebuilding the row. The answer is controlled drying, not placing wet logs immediately beside a hot stove.
What smoke and soot can tell you
Wet logs can cause smoke, but they are not the only cause. Poor lighting technique, restricted air, a dirty flue, adverse wind and an excessive fuel load can produce similar symptoms. Diagnose the whole combustion path. If smoke escapes at a joint, draught stays poor or soot builds unusually quickly, let the fire end safely and inspect the system before the next use.
For a structured diagnosis, continue with the external-stove connection guide and the dedicated smoke article in this programme.
Firewood choices at the store and stove
Which wood species is best for a hot tub?
First use only species and log sizes accepted by the heater manufacturer. Moisture, log dimensions, air supply and local availability often matter more than a universal “best” species.
Can I store logs directly against the house?
Only with suitable ventilation, drainage, fire separation and pest management. An open, inspectable store is easier to control than a dense stack pressed against a wall.
Is a tarpaulin enough?
It can protect the top, but wrapping the sides can trap moisture. Maintain airflow and ground clearance.
Can I burn pallets or construction offcuts?
Not unless you can verify that the material is untreated, uncontaminated and permitted by the heater instructions and local rules. Nails, glue, paint and preservatives make uncertain waste wood a poor choice.
Fuel-quality and clean-burning references
- Department for Environment, Food & Rural Affairs: selling and storing Ready to Burn wood in England
- GOV.UK customer notice: drying and measuring firewood
- GOV.UK: smoke control area rules
Fuel, log size, loading method and clearances are determined by the fitted heater instructions and local rules. Ready to Burn sales rules cited above apply to England; verify the rules where the hot tub is installed.