Once you have learned how to select and purchase lumber you also need to know how to pick out useable lumber. There are a few things you should know about before you select your material. Normally, you want to select kiln dried lumber. Wood not kiln dried is referred to as green lumber. In the construction trade kiln dried lumber is not common. In cabinet making and furniture making it is critical to use dried material. Wet wood will twist, shrink, and cup. Kiln dried can do the same; but the effects will most likely be very minimal depending on the water content.
Another thing that is important to know is that wood comes in the rough, S2S (surfaced two sides) and S4S (surfaced four sides). Wood in the rough has been run through saws; and is like it sounds, rough! Usually, wood in the rough can be found at a better price. However, it is not easy to tell what it will look like; and if it has imperfections. The amount of extra work trying to use wood in the rough is not worth the money you save when purchasing. S2S wood has been run through a planer on both sides; and is usually consistent in thickness throughout the unit of wood. With S2S you can see what your selection looks like; and have a good idea of the quality. S4S is the same as S2S but the edges are machined too. While S2S is good you will still need to machine the edges. S4S is usually ready to be used as soon as you buy it. Once you have decided whether to use material in the rough, S2S or S4S, there are a few more things to look for in your selections.
Unfortunately, even kiln dried lumber can have problems that you need to avoid whenever possible. You need to inspect every board for twists, cracks, cupping, bowing, and checking. Before you look at each piece of material, look at the stack of wood. Is the stack sitting flat or are there gaps in between each board? Are the top boards lying flat? Start by choosing a stack that is lying flat; and you will have a better chance of getting good material.
Select a board; and turn it on its edge, then, sight down the length. Is it fairly straight? If it has a dramatic bow, from end to end, select another one. Is the board flat? If the board is not flat or is cupped select another board. Splits on the ends of the board are fairly common due to the drying process but a long split is not good. Not only is it a waste of money but could keep splitting the longer it sits around.
Checking is another problem due to sloppy drying techniques. Checking looks like stretch marks or gouge marks on the face of the board. Worm holes should be avoided unless that is the look you want.
If you see powdery saw dust by the holes or on the face of the board then there is probably live worms eating away; and not a good idea to bring them back to your home or shop. Large holes in reclaimed wood can have live wasps and Carpenter Bees hibernating inside. If you bring reclaimed wood into the warmth they will come out to visit. Also, as you go through a stack don’t mess it up for the next guy. Go through the stack and restack the pile like you found it.
