When you go to a big box store to buy lumber, some lumber, often sold as appearance boards, has square edges. But construction lumber like 2x4s, also known as dimensional number, has rounded edges. In this blog post, we’ll explore why dimensional lumber has rounded edges.
Rounded edges on dimensional lumber, such as 2x4s, make it easier to process, handle, and deliver the lumber without damaging it during production and shipping. It also makes it less likely to damage drywall when using it for framing.
Why construction lumber has rounded edges
Construction lumber, or dimensional lumber like 2x4s have rounded edges largely for practical reasons. The rounded edges make it much less likely that the edges will damage other pieces or bee damaged by other lumber while they are being processed, shipped to the store, and transported to the job site.
Similarly, on the job site, lack of sharp edges reduces the risk of damaging drywall if the framing isn’t quite perfectly square, or just in the event of lumber or drywall being handled roughly. Preventing damage saves time and expense.
There’s no single reason for rounding off the corners of construction lumber. It’s just that there was enough benefit to the practice that not doing so put mills at a disadvantage. So it became the standard practice.
Some types of lumber have square edges, and that’s one of the reasons they cost more. They are sold for appearance and require more care and handling to maintain that appearance.
How to square off the rounded edges of dimensional lumber
If you want cheap lumber but you also want squared edges for some or all of your project, you can square off dimensional lumber. The trick is to trim about an eighth of an inch off each edge using a table saw.
Make sure to read and understand the safety instructions that come with your table saw and any other power tool before using it. A board getting hung up in the blade can cause kickback, resulting in the board being flung at high speed and can cause serious injury.
That said, after squaring up dimensional lumber with a table saw and then running it through a jointer, you can make much larger boards with glue ups. The results can look surprisingly good. Or you can buy larger 2×6 boards and rip them into nice-looking smaller boards. Larger dimensional lumber is usually made of better wood.
How to round off the corners on boards that have a square edge
Furniture usually has rounded edges to reduce the risk of damage and/or injury from bumping it. If your project involves boards with square edges, you can get round edges if you want. After you finish your glue up, sand the edges with coarse sandpaper to round them off. Start with 60 grit, and once you have the edge about as round as you want it, step up to 120 and then 180 grit to make the rounded corner smooth. Then you can paint or stain as needed.
What the original reason was for rounding the edges on lumber
There are some people seriously overthinking the reasoning behind rounding the edges on lumber. The details of who originated the practice and exactly why they originated the practice, if there was a single reason, are lost to history.
Their reasoning typically comes in the form of rhetorical questions. Let’s take them one at a time.
Why does a supplier care what the lumber looks like in the store?
The supplier cares what the lumber looks like in the store because they care about getting the next order. If the lumber doesn’t sell because people don’t want to buy it because it looks bad, the store can switch to another supplier.
It is an extra step in the manufacturing process, so it does raise the price. But if it means less lumber ending up in the cull lumber bin, that can offset the price.
And when you are talking mass market items like dimensional lumber, consistency it part of the product. The secret to McDonald’s success isn’t its quality. It’s consistency.
Who cares what the lumber looks like?
This is a rhetorical question conflating “not everyone” with “nobody.” It’s like apples in the produce aisle of grocery store. You may or may not have noticed that apples in the grocery store are shiny. Some people won’t buy an apple if it’s not shiny. Some people don’t care. The majority of people have probably never thought about it. But when asked if they would buy an apple that wasn’t shiny, they hesitate.
Not everyone has to care what the board looks like, but it takes a surprisingly small number of people caring about it and making a big deal about it to make a system unsustainable. That number is no higher than 16%. When civil engineers studied the reason the law imposing a national 55 mph speed limit failed, they found it was because somewhat fewer than 85% of citizens complied with the law. You can also observe this phenomenon every July. For about 10 months out of the year, well over 85% of the population is perfectly fine with complying with fireworks laws. But you probably noticed the compliance rate with your municipality’s fireworks laws drops significantly the closer you get to July 4th.
It’s not that everyone is shooting off fireworks, and it’s not even that everyone who isn’t shooting off fireworks is watching. It’s just that the number of people unwilling to comply with the law overwhelm the people who enforce the law.
Similarly, if 85% of consumers just grab lumber and go, it keeps store traffic flowing.
Why do mills round lumber edges when it requires additional expense and equipment?
When it comes to marketing, that is part of the cost of doing business. If enough of your competitors or doing something that consumers or your channel partners start to care about it, then you have to adjust.
In my day job, there have been times my former employers lost deals because a competitor had a feature they didn’t. The feature didn’t do what the customer thought it did, and I guarantee the customer who bought the alternative ended up not using the feature. But not having the feature was a showstopper.
When it comes to selling a product, whatever the product, you don’t just consider the cost of doing something. You also have to weigh the cost of not doing something. In the case of rounding the edges of lumber vs not rounding them, eventually the cost of not doing it outweighed the cost of adopting the practice.
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.