Seasoning firewood is the controlled process of reducing the wood’s internal moisture content to a level that allows for efficient, clean combustion. A freshly felled tree, known as “green wood,” can hold a moisture content of 40% to over 100%, depending on the species. Burning wood this wet is inefficient because much of the heat energy is wasted boiling the water out of the log before the wood itself can ignite. The goal is to bring the wood’s moisture content down to below 20%, which is where splitting the logs becomes a necessary step in preparation.
The Necessity of Splitting for Curing
Splitting logs is mandatory because the bark acts as a natural, nearly waterproof barrier, effectively trapping moisture within the wood round. This “moisture jacket” prevents the natural evaporation process from occurring across the log’s large surface area. By splitting the wood, the sealed exterior is broken, exposing the porous end-grain and the length of the wood fibers to the air.
The interior structure of the log, known as the heartwood, is generally denser and less permeable than the outer sapwood, which retains a higher initial moisture content. Splitting exposes the sapwood and the heartwood, increasing the surface area-to-volume ratio. This exposure allows moisture to escape rapidly along the grain, accelerating the seasoning process and preventing the development of mold, fungi, and insect infestations that thrive in damp, whole rounds.
Optimal Timing: Splitting Immediately vs. Delaying
The short answer to when logs should be split is: as soon as possible after felling and bucking them into rounds. This immediate action is the best practice for two primary reasons related to both the wood’s condition and the ease of labor. Splitting wood while it is still “green,” meaning it still retains its high initial moisture, is significantly easier because the fibers are softer and more pliable. A fresh log splits cleanly, following the natural grain with minimal resistance.
Delaying the splitting process allows the wood to begin its initial drying phase, which paradoxically makes the task harder. As the wood slowly loses moisture, it begins to harden and check, or crack, from the outside inward. These partial cracks can cause the wood to bind and resist a splitting wedge or maul, making the work substantially more difficult and increasing the risk of splintering rather than a clean break.
Delaying also halts the seasoning process. Logs left in whole rounds for more than a few weeks, especially in warm or wet conditions, begin to decay and harbor insects before the moisture content has dropped. For maximum efficiency, rounds should be split and stacked within one to two weeks of being cut to immediately begin the rapid moisture loss phase.
Variables That Influence Pre-Split Waiting Time
While immediate splitting is the general rule, the acceptable pre-split waiting time can be slightly influenced by the wood species and the local environmental conditions. Wood species vary in their initial moisture content; softwoods, such as pine and fir, typically contain a higher percentage of water in their sapwood than many hardwoods. This higher moisture level means they should be split even more quickly to prevent rapid decay.
Thicker logs, those with a diameter greater than 10 to 12 inches, contain a larger mass of interior wood that is sealed off from the air. While these large rounds could theoretically be left longer without decay, they should be bucked into smaller rounds and split promptly to avoid the wood hardening to a point where mechanical splitting becomes difficult.
Ambient air temperature and humidity at the time of cutting also play a role in the urgency of splitting. In hot, humid conditions, a whole log will begin to develop mold and fungi much faster than in cold, dry winter air. When the air is warm and moist, the window of time before the log begins to decay or harden unmanageably shrinks significantly, reinforcing the need for rapid processing.
Maximizing Seasoning Through Proper Post-Split Storage
Once the logs are split, proper storage is equally important for maximizing the final seasoning process. The split wood must be stacked in a way that allows for maximum air circulation to carry away the evaporating moisture.
Storage Requirements for Seasoning
- The woodpile must be elevated off the ground, typically using pallets or cinder blocks, to prevent the bottom layer from absorbing ground moisture and allow air to flow completely underneath the stack.
- The best location for a woodpile is a sunny, breezy area that encourages constant airflow and solar heating.
- Stacking should be done in a single row or two-row formation with the pieces arranged perpendicular to the prevailing wind, leaving spaces between the pieces.
- The stack should only be covered across the top to shield it from rain and snow; the sides must remain completely open so moisture can escape.
- Splitting the logs to a consistent, manageable size, generally between four and six inches across, ensures a more uniform final moisture content and shortens the total seasoning time.