Kiln drying further enhances the natural characteristics of Douglas fir, one of the strongest of all softwood species. With a lower moisture content, kiln dried Doug Fir lumber provides improved resistance to mold and insect damage, with greater dimensional stability that hinders the natural twisting and warping that can occur as green lumber air dries.
Doug fir has incredibly high moisture content at the point of being cut down. Drying is an important step in the process of acclimating wood to a new environment (specifically, drier interior spaces). Drying reduces the moisture in lumber to replicate the future conditions to which the lumber will be exposed. Green doug fir typically dries out in the open in a process known as air drying.
Because it is moderately heavy, Douglas Fir will shrink more in drying than most woods of lighter weight. Volumetric shrinkage when dried from a green state down to 12-15 percent moisture content is 5.4 percent, compared to the softwood range of 3.4-6.6 percent.
Kiln drying is a faster, more precise alternative than air drying. Kilns for wood drying are typically large spaces with heated coils on the ceiling. Nearby fans redirect the flow of warm air evenly around the room. The heat greatly speeds up the drying process in an environment with consistent temperature and humidity. The stable environment also allows for wind control (an important factor in effectively drying wood). Kiln drying can also be carried out in stages through environmental control, which is ideal for drying the wood at an optimal pace.
Hayward offers kiln dried doug fir framing lumber in dimensional sizes, as well as in the larger sizes for beams and timbers.