Welcome back to the second lesson of Lumber 101! We hope you enjoyed the first post about Vertical Grain vs. Flat Grain. Next up is the difference between green lumber and kiln dried (KD) lumber.
What is Green Lumber?
Green lumber refers to lumber that has a high moisture content – freshly harvested logs are considered to have a moisture content (MC) of 100%. Once harvested and sawn into lumber, the wood begins the slow process of air drying. The high moisture content means the wood is softer and more flexible, making it a a great option for carving or turning. Keep in mind that green wood will always dry over time, which increases the possibility of cracking or warping.
Typically, green lumber is best used in outdoor applications where the moisture content will fluctuate with the seasons (rain and high humidity will increase moisture content and wind and sun will decrease moisture content) such as fencing, pergolas, or garden beds. Ideally you wouldn’t use green lumber for an indoor project, but if you do make sure you acclimate the wood first by letting it sit for a few weeks inside a dry location.
What is Kiln Dried (KD) Lumber?
Green lumber is piled with spacers (kiln sticks) in between each layer to improve air circulation and is placed into a dry kiln to extract the internal moisture. Dry kilns have a heat source and fans to circulate the warm air around the lumber, creating an even and thorough drying process. KD lumber is dried to approximately 6-16% moisture content depending on the species, typically this takes between 2-6 weeks. Kiln drying lumber reduces the weight, increases strength properties, improves resistance to bugs/fungus and makes the lumber more stable and less susceptible to shrinkage.
Dry lumber is much more stable to work with, meaning it will retain its size and shape over time, making this the best option for furniture making or indoor application. However, KD wood is harder to work with since the grain is dried out and less flexible, making this a poor choice for carving or turning.
The lumber available for purchase from Lumber Store is primarily green or air dried stock. Please contact us if you are looking for kiln dried lumber and we can point you in the right direction.