When you’re buying lumber for a project, it’s easy to assume that it’s going to be straight and relatively easy to work with. After all, that’s the point of buying milled lumber instead of using rough-cut lumber or pieces you’ve cut yourself.
Unfortunately, even milled lumber can have flaws that will cause you headaches once you start working with it. All anyone can do is select wood that is straight, to begin with. There are internal stresses which can cause the board to bow and twist when it is cut. No two trees are alike, so no two boards will be alike either. It’s just something to allow for by buying more lumber than the project needs so if a board turns out to be a bad one you can replace it.
When you go shopping for lumber, it’s important to keep an eye out for imperfections in the wood. This will help you avoid boards that will just cause you unwanted problems. When using softwood such as pine avoid lumber that is especially heavy. This is an indication it has a high sap content which usually causes a lot of warpage problems when making parts.
Lower Grade Lumber
Some wood just isn’t in good shape. There could have been an infection or rot in the wood or there may have just been something wrong with that particular tree. It may have gone unnoticed at the mill, resulting in lumber that’s weaker than you’re expecting – it might even contain a few patches with a weird texture. Such imperfections should be obvious during a surface check of the wood since it’s hard to get a smooth board out of damaged or defective wood.
Even though lumber should be straight, sometimes the cuts just don’t line up right. Parts of your board may be too thick or too thin or there might be angles in the cut that just ruin the smoothness of the surface. Sometimes these irregular cuts will be noticeable, but that’s not always the case.
Look along both the width and the length of boards, flipping them over to inspect both sides as necessary. If something seems questionable, try placing the edge you want to check on a known flat surface and see if it sets flat. If you see a gap or the other side of the board ends up at an angle, then you’ve obviously got a board that isn’t straight. That being said, lumber is never straight enough to just use unless you are making a crude project. It’s why most of us have jointers, planers and table saws.
You’ve probably encountered knots in wood before and know what a pain they can be. While you might be used to knots in unfinished wood, you’ll find them in milled lumber from time to time as well. Not only can knots cause problems when trying to cut or screw into the wood, but the knot may break free from the surrounding wood when you’re not expecting it. If you plan on staining the wood once you’re finished with it, you’ll find that knots don’t take stain very well either. Fortunately, knots are fairly easy to recognize during a visual inspection.
Cracks and Splits
When shopping for lumber, it’s important to get wood that’s free of substantial cracks and splits. While small cracks on the ends are common and normal Any substantial damage to the wood is likely to keep spreading over time, especially if you build something that will be subjected to daily load stress or temperature/humidity changes. Cracking or splitting along the wood’s grain is especially dangerous since it gives the wood a natural path along which to continue splitting. While you can always cut off the section that’s splitting, that reduces the amount of wood that you have to use and won’t always fix the underlying problem that caused the splitting in the first place.
What to Look For
When shopping for lumber, give the wood you’re buying more than just a cursory glance. Take the time to inspect it on both sides, looking for cracks, splits, and discolorations that may indicate a problem.
Check for knots, noting their size and whether they’re partially separated from the surrounding wood. Feel the wood grain, checking for imperfections in the texture and signs that the boards were improperly cut. Essentially, take the time to inspect your wood for problems before you buy instead of discovering that there’s something wrong after you’ve already started working.
Using Imperfect Wood
Bear in mind that imperfect wood can still be used. Knots and sections of wood with different textures will hold paint and stain differently, so using them wisely can give you a more complex appearance on your finished piece. You can correct cracks and improperly cut wood with careful adjustments.
If you keep the pieces you remove from the boards, you may find a use for them on another project. Just be sure that you realize that imperfect wood may not give you the results you want and be prepared to replace it if it becomes too difficult to use. But, if you’re willing to experiment, by all means, go for it.