Hardwood lumber is often called either “Air Dried,” “Kiln Dried,” or “Green”: What’s the difference?

First let’s start with how we get from tree to board. First, trees are harvested. A harvested tree is called a log. A log is taken to a sawmill, and sawn into boards. A freshly sawn board is called a “green” board, as it still has the moisture from the “water” in the tree. Typically these boards will look and feel wet. Once the lumber is sorted for length and grade, it is stacked with spacers between each layer of lumber to start the drying process. The first part of drying is typically done outside.

Once material is outside drying on these spacers, it is referred to as “Air Dried.” The process of Air drying can take anywhere from 2 weeks to many months depending on lumber thickness and species. Why so long? The cost of kiln drying is very expensive, so lumber manufacturers use the natural sunlight and wind to start the drying process. It’s very similar to hanging your laundry on the laundry line (free) vs. drying in a clothes dryer (cost for electric or gas to run dryer).

After the lumber is around 30% moisture content (30% of weight is “water”, 70% is the wood), manufacturers will load their kilns to start the kiln drying process. This process can take anywhere from 1 to 8 weeks depending on species and the thickness of the lumber species. A kiln is essentially like an oven. Large fans within the kiln move air that is heated through the kiln. A kiln operator also can add or remove moisture from the kiln to insure that each piece of lumber is drying at a similar rate. At the end of this process, lumber will be between 6-10% moisture content, and referred to as kiln dried.

Most companies that make furniture, cabinets, flooring, and many other products utilize only kiln dried lumber. Kiln dried lumber is less likely to cup, warp, twist, and break, which enables manufacturers to make a product that can be enjoyed for years to come!

Kiln dried lumber is often used for furniture, cabinets, and flooring.

Air dried lumber is often used in patio furniture, fencing, and decking.

Green lumber is mostly utilized in the pallet industry.

It all begins with an idea. Maybe you want to add a custom table to your office, a desk to your work space or coffee table to your family room. Selecting the right type of lumber is critical. I will carefully select lumber, purchased in person, for your project. My preferred lumber types are mahogany, white oak, cherry, walnut and maple. Maybe you like a quilted or highly figured piece of wood - we can work together to make the right choice. North Carolina offers a wide selection of locally sourced hardwood lumber to fit your needs.

If an exotic type is what you prefer, we can discuss what options are available as imported locally and find the right fit.

While kiln drying and bug kill cycles are necessary, certain types of beetles can add character to an otherwise boring piece of timber.

As pictured, the Ambrosia Maple is technically not a specific species of Maple, but rather a general description of Maple that has been infested by the Columbian timber beetle. Beetles bore into the trees, giving it that discolored look. The beetle carries a fungus, which causes flagging above and below the holes; the beetle cultures and feeds on the fungus.

Another often misunderstood wood defect is spalting. Spalted wood is any wood that has begun to decay or rot as a result of a specific range of airborne fungus. It is created when white rot fungus begins growing within a piece of wood or log.

In order for spalting to occur within wood, there are three conditions that must be present in order for the fungi to grow properly. Those factors are: temperature, oxygen and moisture.

Spalted wood is very popular among wood turners or those who cut pieces using a wood lathe. The random lines and and patterns in the wood can make some amazing designs in wood that is turned or made into rounded shapes. Some examples of this are handles for utensils, urns, pens and bowls.

Spalted wood is not limited to only those who turn it on a lathe though. It can also be used on larger pieces such as table tops and even guitars. Prices for boards that are large enough for tables can get expensive due to the size and the scarcity factor of spalted wood in general.

Yes, it does. In fact it never stops. Three facts to understand about wood movement are; 1. All wood moves, 2. The wood will not stop moving and 3. Trying to constrain or restrict the movement will result in failed joints or cracked furniture.

Lumber shrinks while drying until it reaches a point of equilibrium with its surrounding environment. Even then, wood still takes on moisture and expands in the humid days of summer, then releases water and contracts as the air dries out in winter. A finish may slow the rate of expansion and contraction, but it will not stop it. Neither will securing wood to something seemingly unmoving, such as a plywood panel, a table base, or even a sturdy piece of steel—that only sets up a cause for wood or joint failure.

Keeping in mind the type of wood, grain direction and project, the joinery used will account for movement in the wood allowing for seasonal expansion and contraction.