Now that you know the difference between European and North American kiln-dried lumber standards (see Part 1), it’s up to you to make sure the lumber you buy is appropriate for your particular climate. If you’re working with an African or European species, you’ll want to be especially careful to check with your lumber dealer about the moisture content of the materials they have to offer. Also, go with a reputable dealer that follows steps for quality control when it comes to re-drying the lumber down to North American standards.
Important Quality Control Steps for Achieving a North American Standard Moisture Content
Getting the lumber down to North American moisture content standards isn’t as straightforward and simple as just sticking the lumber back into the kiln for a while. Some steps should be taken to get the job done right.
First of all, boards scattered in different places throughout the pack of wood must be tested for moisture content instead of just the boards on the outside of the back. The boards on the outer layers and inner layers of these packs can vary in their moisture levels due to the amount of exposure to the elements and temperature the boards experienced on the long journey to the lumber yard.
After these boards from at least three different places within the pack have all been tested, the results that they yield should be carefully recorded. The lumber can then be sent through a Vision Tally System that will quickly and accurately record the number of boards in the pack as well as their footage.
The next step in the process is allowing time for the boards to air dry in the lumber yard. That will help them to reach equilibrium in their new environment.
Once in a while, the moisture meter readings differ from one another significantly. When this happens, there’s an extra step to the process: oven testing. After getting the sample’s weight measurement, then drying it in the oven to get the moisture out of it, it will be weighed once more. This test will help to determine the actual moisture content for the lumber if there’s any doubt based on divergent moisture readings.
All the lumber in the pack should be air-dried no matter what the moisture content numbers turn out to be. That’s because newly arrived lumber can pick up extra moisture from being inside of the shipping containers as they cross the ocean. This is true regardless of the time of year.
Stacking and stickering the lumber for several weeks can make a huge difference when it comes to consistency and accuracy in determining the moisture content. It also allows for extra drying so the lumber can acclimate to North America’s typically drier climate. Each species may require a different amount of air-drying time. It can also vary based on the pack’s initial moisture content readings. You certainly don’t want the lumber taken to the kiln prematurely as doing so could cause future complications for the lumber.
In our final article in this series, we’ll explore the benefits of kiln drying lumber and explain why it is so necessary.