Underwater lumber

Q: We are thinking of using some lumber sawn from logs that have been underwater for nearly 100 years. Our tests indicated a few drying problems and machining problems. What information do you have that might help?

A:  I have seen some of the logs from Lake Superior and the wood sure is beautiful. But this wood is indeed different than our wood today. This difference results not because of growth differences in the tree. During log storage under water, there were also some other things going on.

The big question is: "Why is this log underwater in the first place?" As probably everyone knows, North American species of wood tend to float in water. So what changed to make this particular log sink? The answer in many cases is that the tree from which the log was sawn had a bacterial infection.

One of the side effects of bacterial action is that the tree MC increases in the butt log to well over 100 percent MC. There is more water by weight than there is wood. Many of the air bubbles in the cells that normally provided buoyancy are eliminated. (Did you know that if you eliminate all the air in wood, that it is 1-1/2 times heavier than water?.) As a result, the butt logs often won't float.

The higher MC means longer drying. In addition, these bacteria also weaken the wood. In the tree, this weakened wood will often develop shake (a separation parallel to the rings). In drying, many defects, especially checking, cracking, splitting and honeycomb, will form even when using standard drying procedures. Further, after drying, the wood is weaker than normal, leading to machining problems. There is also a chance that the bacteria may give the wood a peculiar, unpleasant odor.

For logs submerged in warm water, bacterial action (if present) can continue even under the water. The sapwood and the out heartwood have the highest risk.

So, based on my experience, I think that submerged wood has a high potential for success as the grain characteristics can really be superb. Further, it is exciting to think that a piece of wood is a century or two old! With a change in processing (drying and machining especially, contact me if you need some specifics), the wood can often be easily handled, unless there has been a severe bacterial infestation. The use of sunken wood for load bearing items (chair legs, hammer handles, etc.) would be ill advised, due to the likelihood of lower strength.


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About the author
Gene Wengert

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 45 years. He is extension specialist emeritus at the University of Wisconsin-Madison.