I get this question a lot ever since building my Nicholson inspired workbench.
Has your workbench exploded yet from the twisting and warping that has undoubtedly occurred as a result of your use of those wide construction grade boards?
OK. So maybe the questions aren’t worded exactly like that. But I do get a lot of questions about using wide construction grade lumber for a workbench and how to prevent the resulting bench from self destructing. Personally I think this concern is a bit over hyped, but there are some things you should do when building your bench to make sure you don’t have too many problems down the road.
The #1 trick to using wide 2X construction boards for a workbench is to make sure they are dry before you use them. The construction grade 2X stock that many home centers carry is not kiln dried. This means that the miosture content of that stock is going to be very high. Too high to work with right away. If you can, find a supplier who sells 2X stock that has been kiln dried. I was able to buy kiln dried 2X stock for my workbench. So once I brought the boards into my shop and left them stickered there for a couple of months, I could be sure they wouldn’t move much after building the workbench. Since the boards will stay in the shop after the bench is built, the best place to equilibrate them is in the shop space.
If you are not blessed with a supplier in your area that sells kiln dried 2X material, all is not lost. You will simply need to let the boards sit and dry for much longer than you will with kiln dried stock. Bring them into your shop, stack and sticker the boards, and let them sit for several months. Check the moisture content once every week or so and don’t work with the boards until the moisture content stays relatively constant. After they are dry, you may have to re-flatten them, but if you chose your boards carefully, you may not have to flatten them much, if at all.
That brings me to tip #2 for using wide construction grade timber for a workbench. Choose your stock carefully. Even if your stock is kiln dried, but especially if it is not, you want to choose boards that were sawn as close to the center of the tree as possible. This will give the board the greatest amount of “quarter sawn” grain as possible. Wood moves the most in a direction that is tangential to the growth rings. This causes flat sawn boards that are close to the bark (those with near horizontal growth ring patterns on their ends) to cup severely when they move. However, boards sawn close to the center of the tree will cup much less, even if they were not kiln dried. After the boards have sat in your shop for several months, choose the ones that have cupped the least to use for the aprons and top boards. Those with the most cup should be ripped into narrower boards for use as stretchers and cross bearing braces for underneath the top.
This brings me to tip #3. Use the absolute widest and longest boards you can find. Wide, long boards need to come from wide, tall trees. In addition, the widest boards are sawn from the areas of the log that are closest to the center of the tree. Don’t try to save money by purchasing 2x4s for the stretchers and cross bearing braces. These boards are likely to twist and warp on you. These benches are inexpensive enough to build from wide stuff. Trying to save another $10 by buying 2x4s instead of 2x12s will make you curse construction lumber workbenches. Get all of your parts from 2x12s, and the longest ones you can get at that. If you can find 20 footers, they are likely to be flatter and straighter than 8 footers. The bench will cost you a bit more, but you’ll be happier and have a bench with fewer knots in the end.
With workbenches made from DRY construction grade lumber, once everything is assembled, movement is actually very minimal. Contrary to popular belief, softwoods like pine, fir and spruce are extremely stable, when they are dry. Softwoods get a bad reputation for being unstable because they are usually still wet when they are purchassed. Construction lumber is not typically dried to the same level as hardwoods for fine woodworking (at least not here in the States). So as the wood continues to dry, it will typically move. However, once it has been dried to the same level as the hardwoods typically are, most dry softwoods are actually more stable than most dry hardwoods. So the #1 factor in getting a good, stable and flat workbench out of softwoods is to make sure they are adequately dried before you start building with them.
I built my workbench several years ago and have been working with it regularly ever since. It does not have any kind of finish on it, so it is fully exposed to all the humidity swings that occur during the year. I have needed to re-flatten my workbench top exactly one time since building it, and even then, it had moved so little and was so barely out of flat, that it took me less than 10 minutes to do the job. I have no doubts that constrution grade lumber can make a fantastic workbench. With just a little up front preparation, you can have a workbench that will last you several generations without spending a fortune. Being built of construction grade lumber, I am also not afraid to ding it up, scratch it, spill stain on it, drip glue on it or hurt it in any way. I treat it like a workbench, not a piece of furniture, and I know I can replace the top for $20 if it ever gets too far gone. So don’t fear wide boards. Wide boards are your friends.