American Hophornbeam for Timber Frame Pegs

Hornbeam and Hophornbeam are not well known these days, but were valued historically for strength and hardness. June 9, 2007

Question
I am in the process of starting a timber frame project. Historically, locust was often used for pegs. Unfortunately, I do not have any locally. I do have a significant amount of American hophornbeam. However, I can not find any information regarding shear strength. I have found articles regarding its use as tool handles and fence posts, suggesting good strength and decay resistance. Anyone have numbers to compare to other hardwoods?

Forum Responses
(Sawing and Drying Forum)
From contributor T:
I haven't seen that info. What I have seen is much confusion among the experts on the common names. American hornbeam (Carpinus caroliniana) is aka blue beach, muscle wood and ironwood. Eastern hophornbeam (Ostrya virginiana) is aka ironwood. They are not often distinguished in technical documents and often erroneously interchanged. Maybe that's why technical info is hard to come by.

Settlers revered Eastern hophornbeam for its strength, durability and rot resistance. That's why it was used for wagon wheel hubs and axles. In other words, they used it where it counts. Most woodworkers don't like working with it because it is so hard, heavy and dulls tools quick. So it's now a forgotten wood.

My own experience with American hophornbeam suggests it is hard, heavy, and strong, but very prone to rot.

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From the original questioner:
I have both hornbeam and hophornbeam on the property. I have found that hornbeam rots easily, but hophornbeam is relatively decay resistant.

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From contributor S:
About how many pegs do you think you will need? Do some horse trading for a locust log if it is locust that you want for pegs. Cut off some slices and start splitting out the pegs. Square pegs for round holes! Actually, the peg should just hold the joint, the joint should hold the load. Transferring much load through the peg seems to be an iffy joint design.

Just for kicks, you should check out a book about Japanese joinery. I have one that is way over my skill level, but still interesting reading.

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From contributor V:
I too have hornbeam and hophornbeam on my property. The hornbeam does indeed rot very easily, and the hophornbeam is a little more decay resistant. Hornbeam turns beautifully, but hophornbeam doesn't no matter how sharp your gouge is; it likes to tear out, but this is no concern if you are turning your pegs. I would still go for locust pegs if at all possible.

I have a customer who brings me barn beams which I resaw for him into flooring material. I have found that tennons should bottom out into mortises, otherwise the pegs will sheer into three pieces. I have also found that about 50% of mortise and tennon joints have some sort of rot, if not completely rotted. I guess if there is any kind of roof leak, and water trickles down the beams, it collects in these joints, eventually causing the timber frames to collapse. Also, if the joint is loose, it is heaven for bugs.

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From contributor B:
The Timberframer's Guild did a sheer test on several wood varieties used for pegs a few years ago. The tests were conducted at a major university with a special machine devised for the test. As I remember, hornbeam had the highest rating for the number of foot pounds of sheer force needed to break the peg. As the pegs are all within the "dry in" area, decay resistance should not be much of a factor.