Eastern Hemlock for Post and Beam Construction
1. Can I use hemlock to create the inner skeleton (post/beam framework) for such a project?
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).
From contributor R:
I've used hemlock right off the mill here in West Virginia for building. It doesn't shrink as much as other woods. My guess is it is as strong as or stronger than white pine and it does not warp. The butt logs have shake in them sometimes. It will show up as a black streak. Just throw those boards out because they will break real easy.
From Professor Gene Wengert, forum technical advisor:
Eastern hemlock is an acceptable species for construction. However, many of the older, large trees are infected with a bacteria that makes the wood very weak and mostly useless, as contributor R has indicated. The butt log is the best part of the tree, so to lose it is tough financially. Yields will be poor. For post and beams, this could be serious.
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.
From the original questioner:
It seems I'm getting some pretty consistent feedback, even from an offline responder. I've already run into a 30" diameter trunk that burst into some 60' long feed troughs when it fell and hit a large rock when cut. Hopefully, since I have such a large quantity of timber with a lot of younger trees, I'll be able to pull enough post and beam grade logs to finish my project.
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?
From contributor S:
I've built several timber frames out of Eastern hemlock and think it is well suited, being stronger and more insect-deterrent than white pine. Some larger logs have shake, as noted, but this is immediately obvious when felled.
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?
From the original questioner:
Thanks. Good info. As for why hide inside the building, the timber frame will be exposed within the ground floor common area, supporting a second floor living area above. The slab has been roughed in and poured and the building has already been purchased and is about to be assembled. I have plans for a number of other smaller cabins for my children to be built on the same property and hope to use post and beam construction atop an 8' high slip-form concrete/stone basement wall, each cut into the side of some fairly steep hillsides.
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