Once you understand the fractions behind lumber thickness, you probably won’t be surprised that 4/4 lumber is the most common thickness within the U.S. lumber industry. In fact, you’re probably so used to thinking that 4/4 is “normal” that you may not even have realized that it’s strictly a U.S. preference; the global lumber market typically prefers thicker lumber.
The increasing popularity of African species such as Sapele and Utile has apparently led to a practical shortage of thinner exotic lumber. That’s not to say that there is a shortage of African hardwood species, at all — simply that the amount of thinner boards isn’t keeping up with the U.S. demand for them. Is there change on the horizon? Probably not. Let us explain why.
We’re Just a Single Slice of the Global Market
While the U.S. lumber market is significant, it’s also very particular. While we’re not exactly sure if the European and Asian propensity to order thicker lumber is due to matching historical styles which call for thicker boards, or because thicker lumber offers greater stability in wetter climates, the fact remains that 8/4 and thicker lumber is preferred on those two significant continents.
Add to that, the fact that sawing 4/4 lumber requires added labor and leads to added waste, and it’s clearly in a mill’s best interest to saw a significantly greater volume of thicker lumber. It makes more fiscal sense for mills to focus their energies on sawing the thicker stuff.
We’re Not the Easiest Slice to Accommodate
That’s not to say some don’t have North American production runs at times. The truth is, though, those sessions usually result in a net loss for the mill. Let us explain.
First, sawing 4/4 lumber ends up resulting in lower quality boards, because it requires sawing closer to the edge of a log. The edges of logs include more sapwood, which leads to common-grade boards. In addition, the thinner stock lacks stability, which often leads to compromised quality during the extensive transportation and drying processes.
When you add to those issues the fact that Americans are pretty picky about only accepting A grade material (something we’ve discussed before), a 4/4 run ends up meaning far more waste than salable boards. Understandably, mills typically end up sawing only 8/4 and thicker boards.

There’s a Niche Market for In-Between Thicknesses
If you’re not involved in the window and door industry, you may not realize that the typical U.S. window and door manufacturing company prefers a thickness between 4/4 and 8/4. Lacking the high degree of waste caused by sawing 4/4 lumber, a market for 5/4, 6/4, and 7/4 lumber has emerged. Sawing for those thickness is still a pretty risky business for mills, though. They’re either hard to find or expensive to attain.
Now that you understand the problem, how about a solution?
Read the Series
• Lumber Math: Fractions You Need To Know
• Lumber Math: Understanding the Board Thickness Dilemma
• Lumber Math: Possible Solutions for Board Thickness Dilemma
• Lumber Math: Plywood Ply Number Isn’t Always Important
• Lumber Math: Shorter Boards Can Be Better & Save You Money
• Lumber Math: Sometimes Less Is Really More