Ring Shake in Hemlock
Hemlock makes good boards or framing lumber, but wood from trees exposed to grazing animals may be have structural flaws. July 12, 2005
Question
I have a neighbor farmer who is offering me cut Hemlock logs. Their diameter is 16"-24" by 22-30 feet long. They all have little taper. The farmer told me that all hemlock is subject to ring shake and doesn't make good boards. I am wondering, what should I to do with them? Any help is appreciated.
Forum Responses
(Sawing and Drying Forum)
From contributor F:
I dont know about eastern hemlock, but the farmer is wrong about all hemlock. I live in Oregon, and the hemlock that grows here is widely used as lumber. A lot of it is sawn vertical grained and sold as molding stock.
From contributor B:
Hemlock does suffer from ring shank more often than most species, but it still makes good boards. When dry, it can be splintery, so it's most often used as construction lumber. Here in New York, it has traditionally used as barn siding.
From Gene Wengert, forum technical advisor:
Shake in eastern hemlock is indeed common especially in trees over 100 years old. It is also common in western hemlock, where the moisture content is also increased creating what is known at sinker logs (they do not float in water). Often the shake seems minor when sawing, but becomes very obvious when drying (but it is not a drying defect). Naturally, it depends a lot on the wetness of the site where the trees are grown, as well as soil disturbances. Much of the work on this was done by Jim Ward over 25 years ago at the US Forest Products Lab.
From contributor R:
I've cut a lot of good hemlock, but if the farmer warned you of ring shake I wouldn't waist my time. If a board has ring shake, it can shatter into splinters just by dropping it on the ground, and this is unsafe lumber for anything. I have heard that hemlock that grows around pastures is subject to this kind of shake. Some lumber that comes from dry areas has this problem. I have had to box out the center on some large trees also.
From Gene Wengert, forum technical advisor:
It is true that hemlock, and indeed most species, that have cattle grazing in the forest will have ring shake. This is because of bacterial infections, which have been discussed here before. The animal's hooves damage the roots, allowing the bacteria to enter. The risk is greatest in wetter soil, which hemlock, among many species, prefers.
