Rotten Wood or Good Wood
It isn’t my main business, but I mill lumber for customers on occasion, since I have all of the equipment and I have a hard time saying no. Often they will have a log in mind that they found laying in the woods or even one that they intended to mill sooner, but just never got around to it. Anyway, the log looks less than fresh and they want to know if they should spend the money having it milled.
Of course, I need as much information as possible before I can answer them, but there are some rules that I use to decide. First of all, think of logs as produce. For the color to be the brightest, with as few defects as possible they should be milled quickly. If they have been sitting for a while, I try to determine, in this order, what species the logs are, how long they have been on the ground, what seasons they have been through, and the environment they have been stored in (shady and wet, high and dry, etc.) and finally what it will be used for (hopefully something rustic).
Species is first because logs decay at different rates. For example, silver maple starts to discolor in just a few weeks in the summer, while walnut can sit for years and the heartwood will show no signs of its age. Woods that are white are the first to go, because, as noted in an earlier post, the white wood is the sapwood and it rots
much faster than the heartwood. Next to go are some open-pore hardwoods like red oak and honey locust. Last to go are logs like cherry, walnut and white oak.
For fun, I have photos of a white oak that I just quarter-sawed that inspired this post. Notice that the sapwood has turned to foam, falls apart in your hands, and has big beetles in it (I have regular size hands).
The difference in the heartwood is amazing. It was like a brand new log on the inside. I don’t know how long this log sat, but it was definitely years.
After considering species, time on the ground is the next indicator as to the soundness of logs. Here are some estimations based on three groupings. White woods will be absolutely no good after about four years, show considerable age after just one and be off in color after a couple of months. The open-pore hardwoods like red oak will be worthless in about five years, show their age after two years and start to be off in color in the heartwood after four. The heartwood of the third and final group can definitely go much longer. White oak and cherry heartwood will begin to discolor after six years, but have sound lumber for much longer. Walnut, as far as I can tell, never rots. I’m sure it does, but very slowly. Walnut is the last log I cut because I know it will not go bad on me.
All of these logs can start to show some signs of age after a short time depending on the season. During the summer the logs will get bugs in them and the heat can quickly cause discoloration. These problems will be worsened if the logs are stored in a wet spot versus a spot that is dry. The
winter is the best time to store logs. If it is cold enough, almost no degrade happens and the bug issue is moot. If stored in a shady and dry spot, off of the ground, and in the winter the logs will last the longest.
The last thing to consider is what level of degrade is acceptable, knowing that logs that have sat for more than a couple of months will have some “character”. Worm holes and spalting are common and can happen quickly in the summer, but still leave the lumber stable. Even lumber that is structurally impaired can be used for panels and other areas just for show. If you are alright with less than perfect lumber than you can easily use logs that have sat for a long time.
When checking on a logs condition, simply cut the ends back a couple of inches to see what is inside. Logs rot more quickly on the outside and from the ends. Trimming the ends may reveal wood in the middle that is still good, or it may not. Look at the color and check the hardness of the wood. If the color is marbled or there are soft spots, the wood is decayed. If it seems too soft/rotten, trim back further, a foot at a time, until you get to solid wood. If you get done trimming the ends and the remaining log is firewood length, your log is too rotten to mill.