Question
I have a large quantity of eastern hemlock in the hills of southeastern Virginia that I am being told to use or lose due to beetles coming our way. I also have a building project of a rather urgent nature and want to use this timber for post/beam framework inside a steel building as a residence. I can get a sawyer to mill the timber to my specs with no problem. Drying it afterwards is going to be a huge problem. No facilities!
1. Can I use hemlock to create the inner skeleton (post/beam framework) for such a project?
2. How much curing does this type of wood require prior to use?
3. Can we secure the steel building to the timber frame for strength/stability?
Forum Responses
(Sawing and Drying Forum)
From contributor S:
I have experience on the left coast, in softwoods. I realize your trees are likely not the same. We cut mostly softwood, Douglas fir, spruce, hemlock, white fir and cedar. Hemlock has the same mechanical strength classification as all the other softwoods except for DF which is higher.
Hemlock comes to me very heavy, lots of water in the log. It cuts well, but is heavy to offload parts. My sawmill and support equipment has no trouble handling it, but you will need to prepare for some form of offloading.
Dry time in beams is a bit of a misnomer. I won't bite on that issue. I would recommend you use a design that is insensitive to shrinkage. I live in a wet climate and even air dried material tends to grow after I install it (doors or window made in my shop). That is the beauty of wood.
I would think you have a wealth of good material. It takes a bit of practice to make good true beams. I recommend watching the stress effects and rotating the log 180 degrees to accommodate for it. I also tend to take a cleanup pass to ensure conformity (assuming you are using a band mill).
In WV the issue is a bit less than in wetter, warmer locations, so you might have a big problem. Cut a few large trees and see how much shake you have, as shake is a 100% predictor of bacteria. I have had clients that stopped cutting eastern hemlock in a project after just a few hours. The smaller tree, perhaps 50 years old, is often still pretty good. Watch the butt log of older trees.
I was also advised to cut, mill and let them dry in place. This will likely work well and allow them to dry slowly since they'll be exposed, supporting an upper floor, in this metal building. I'll look for the optimum MC rate of drying (% per day) and shoot to maintain an environment conducive to that rate.
My only other option is to perhaps trade viable green timber to the sawyer for some cured, construction-ready beams. Anyone know of such a person in the Tri-Cities area of east Tennessee?
There is no such thing as thoroughly-dried timbers unless they've been cut many years (or run through an RF/vac kiln, which is very expensive). There are sources here in Western NC for pine timbers that are somewhat air dried, but there isn't much advantage when you have the material on hand. Traditional joinery allows for normal shrinkage without compromising structural integrity.
Sawing the timbers with the heart as centered as possible is important, and any 4/4 side lumber if sticked and under tin will be 10-12% or so within 6-8 months. Although the material that one buys from commercial sources has in most cases gone through a dry kiln, frequently this is only to kill insects - I've had readings in the 30-40% range in framing material and 20-30% in finishing material from the supplier. Thoroughly dry finishing material is imperative, but not so much with structural members.
Employing techniques that will allow the wood to dry in place without unduly affecting the joinery/visual effect are always a good idea. The wood frame can certainly be integrated to the steel building - a properly designed structural scheme shouldn't make for substantial shrinkage in any major dimension of the wood frame. Why disguise a nice timber frame inside a steel building?
