Remember learning all about fractions in elementary school? You always had to reduce them to mixed numbers and all of that. Mrs. McGuffy was a stickler about it. You can still remember her deep red pen markings all over your math page, reminding you. Well, forget it. All of it. When it comes to the lumber industry, what may look like improper fractions begging to be reduced are really the official terms for various thicknesses of lumber. Mrs. McGuffy will just have to deal with that.
What the Fractions Mean
Lumber thicknesses are described by “quarters.” A one-inch-thick rough sawn board is described as “4/4” or “4 quarter.” If that doesn’t make you cringe, then the 2-inch board called 8/4 (or “8 quarter”) might. At least the translation makes mathematical sense: reduce the fraction to get the thickness in inches. Hopefully you already feel a little better equipped to intelligently place your next lumber order.
Where the Fractions Started
This might just veer into the category of lumber lore, but everyone seems to have a theory about when and why the fraction jargon got started. Many sawyers and other professionals within the lumber industry seem to concur that this unusual way of describing thicknesses came about as standardized sizes became more important.
Originally, local mills expanded to ship their lumber across the region and ultimately across the nation, which required a standardized way of describing size. Because ½-inch increments would lead to excessive amounts of waste and 1/8-inch increments would lead to a ridiculous amount of stock sizes to keep inventoried, ¼-inch increments made sense.
At first, “quarter” was a term that referred to the number of stops on the log carriage, sliding the log over and locking in the thickness of the board. The stops were set to mirror the ¼-inch standard, so by bumping the log carriage to the fourth quarter, a sawyer would produce a 1-inch-thick board, also known as a 4/4 board. To clarify, this theory hasn’t been completely confirmed, but anecdotally, it seems to hold water.
Why the Fractions Matter
Whether you remember (or believe) the story of how the fraction-based thickness descriptions originated, it’s good to know that when you hear lumber described in this way, you know that rough sawn lumber is being described. As a result, you can expect the finished board to be smaller than the numbers denote once it’s planed, jointed, or both. Not only will this knowledge help you plan appropriately when ordering, but it will also (we hope) prepare you for the fact that these boards will need to be milled. (If you don’t have milling capabilities in house, we can help you with that.
To learn a little more about lumber size designations and why they matter when you’re placing an order, continue reading here with Part 2.