What’s the Difference Between Kiln-dried and Air-dried Western Red Cedar?
When it comes to understanding the world of cedar, there are few people we trust more than “Mr. Cedar” himself, Paul Mackie. He’s been with the Western Red Cedar Lumber Association—known as the “voice of the cedar industry”—for more than two decades, working to represent quality cedar producers and educate others on all things cedar. In this series, he’ll share everything cedar-related, from what exactly western red cedar is to the difference between kiln- and air-dried lumber to installation best practice.
In this video, Paul discusses the following:
Kiln-Dried vs. Air-Dried Western Red Cedar
In the marketplace, western red cedar might be available unseasoned (or green), which means it hasn’t gone through a drying process—the moisture content of this wood could be up to 25 percent moisture. To finish the wood, it has to be at 20 percent moisture content or less, which is why drying is important. In some markets, material may be air-dried on racks or put on stickers in a well-ventilated place to dry naturally. Other manufacturers use dry kilns, which dry the material to a targeted moisture content based on whether the material is clear or knotty.
Moisture Content for Clear vs. Knotty Material
Most mills target 17 percent moisture content. Kiln-dried clear material is usually dried between 12 percent and 15 percent moisture, while kiln-dried knotty material is dried between 15 percent and 19 percent moisture content. Because the knots are denser than the surrounding material, knotty material has a tendency to star-check. If it gets too dry, the knots may chip as the materials runs through the planer, resulting in a lower-grade material. That’s why knotty material is dried to a higher moisture content than clear material is.
Drying Western Red Cedar for Exterior Applications
In most places in North America, the ideal moisture content for installing western red cedar in an exterior application is 12 percent. In moist areas where there’s a lot of rain, it might be as high as 13 percent or 14 percent, while drier areas might be lower—around 10 percent. If you need just one number to remember, the target for moisture content is 12 percent. Clear material that’s been kiln-dried to somewhere between 12 percent and 15 percent is almost ready to be installed—it might require a day or two of proper job site storage to get it down to 12 percent if it’s a little high. For knotty material (dried to about 17 percent), you’ll need to go through acclimatization on the job site to get the cedar as close to 12 percent moisture content as possible before it’s installed.
Watch previous parts of our series with Paul here, and stay tuned for more from Paul as we continue to learn from him on Dunn Solutions over the next few months. For more on western red cedar, click here.
