Wood Drying Time Calculator for Lumber

Wood drying time is an factor that determines the stability of the finished product that are made from wood. The drying of the wood impacts whether a finished product will remain flat or become twisted. The process of drying begin when the tree is cut, at which time the sapwood and the heartwood contain different amount of water.

Because of these different amounts of water, the various parts of the wood behave differently after it is processed into wood board. Removing the moisture from the wood at a steady pace ensure that the wood will remain machinable and that the wood will not experience checking, cupping, or staining. While many people focus upon the species of the wood as a factor that impact drying time, the species of the wood is not the only factor that impacts the drying time of the boards.

What Affects Wood Drying Time

For instance, species like oak are denser than other type of wood, which allow them to contain more water. Thus, the water in oak is released at a slower rate compared to lighter species like cedar and pine. Additionally, the thickness of the wood is another important variable.

The moisture must travel from the center of the board to its surface. Thus, a board that is twice as thick does not necessarily take twice as long to dry, but the drying time will increase due to the center of the board retaining it’s moisture even after the surface dry. The factors that help to control the drying schedule for the wood include the method in which the wood is stacked and the amount of airflow to the wood.

Placing stickers for the wood too far apart allow the boards to sag, which traps still air within the boards. Placing stickers too close together will choke the airflow to the wood. Additionally, a covered wood stack placed in spring weather can dry more effective than open wood piles in the summer.

Summer weather experiences more humidity and temperature fluctuation than the winter months, which can work against drying the wood. Kiln drying can shorten the drying time of the wood, but does not remove the difference between species of wood. Thick oak can be dried in a conventional kiln faster than air drying, but the schedule for the kiln must be careful to avoid having the wood check.

Solar kilns and dehumidification kilns allow for more control over the drying process than air drying alone, but still require monitoring to ensure that the drying processes are even. Additionally, the target moisture content impact drying time. The moisture content of the wood will impact whether the wood will dry to reach the moisture content necessary for furniture in a heated house compared to decks that will be exposed to the outdoor element.

Air drying alone will not dry the wood to the necessary moisture content in regions that is humid year-round, and may require additional conditioning to reach the target moisture content. Depending upon the use for the dried wood, specific method should be used in relation to wood drying. For instance, wood that will be used for tabletops will have more requirements for moisture content than lumber that will be used for framing.

A calculator is available online that will allow an individual to calculate the drying time for wood by entering the species of the wood, the thickness of the boards, the method in which the boards are to be stacked, the airflow to the wood, the temperature of the drying environment, and the humidity in the environment. Such a calculator will provide an estimate of the number of days that will be required for the drying process, the daily rate at which moisture can be lost from the boards, the equilibrium point for the moisture in the wood within the climate in which the wood will be dried, and the hold time for the wood to allow for the equalization of the moisture within the core of the wood versus the shell of the wood. These factor will allow an individual to determine whether the drying schedule that is proposed for the wood is realistic.

The most common mistake with wood drying are made when the different drying factor are considered to be independent of one another. For instance, increasing the airflow to the wood without adjusting the spacing of the stickers can lead to a loss of the drying time that was calculated for the drying process. Additionally, drying thick boards made of species like oak too quick without adding end seals may result in the wood checking.

Finally, attempting to dry the wood to a moisture content of six percent in a region where the air humidity remains at ten percent will result in the drying process stopping when the moisture content of the wood reaches six percent, as the wood has reached equilibrium with the surrounding air. To avoid such mistakes, an individual may choose to check the moisture content of the core of the wood. Using a moisture meter to measure the moisture content of only the surface of the wood may indicate that the moisture content of the wood has reached the moisture content that is appropriate for the use of such wood, but the core of the wood may still contain moisture.

That extra moisture within the core will even out once the wood is milled, but will result in the movement of the wood after milling. Adding an equalization hold time for the wood to even out the moisture in its core can help to prevent such a problem. Wood drying time is a process that can be managed according to the purpose of the wood that will be produced.

The species of the wood, the thickness of the boards, the climate in which the wood is dried, and the method in which it is stacked are all connect variable. By considering each of the variables to be connected to each other, an individual can more successfully manage the process of drying wood for specific project.