Sycamore for a Post and Beam Frame?

      Beautiful as the wood is, Sycamore's tendency to twist makes it a questionable choice for timber framing. December 28, 2006

I'm planning on building a post and beam house with sycamore that is on our land. The trees are tall with few branches, so it seems they would work well. We can cut and mill them this winter, and I'm getting a DH kiln for drying 4/4 and 5/4 sycamore for the flooring and ceiling. Are there any reasons not to use sycamore for beams? How do I keep them from staining? Can they be partially dried in the kiln?

Forum Responses
(Sawing and Drying Forum)
From contributor T:
Sycamore has a reputation for twisting. If the beams and posts twist, you will spend a lot of time dealing with this. I'm not sure how strong sycamore is. Check load tables to be sure your beams will be large enough to carry the calculated loads. Not saying don't do it, just a couple of things with which you should be concerned. Timber framing is fun, but a lot of work. Is sycamore hard enough for flooring? Quarter saw all 4/4 and 5/4 material for more stable wood.

From contributor D:
Sycamore can be notoriously unstable. It commonly has a spiral grain that makes it prone to twist. I would take great care to cut beams only form the straightest trees. Trees that have tension wood where the bole of the tree has lean or sweep may be more twist prone.

From contributor R:
Besides what has already been stated in regard to instability, you need to have an engineer design your timber frame for you based on the species of wood you plan to use. Not all species will have the same bending strength or deflection ratios. That said, I would personally be very concerned with the twisting characteristics of sycamore. I would not want to saw any more timber than I can work in a few months and get it joined and assembled quickly. If you saw beams to required dimensions and it twists like I have seen it twist, you can see many of your beams become firewood before you can join and assemble your frame.

From contributor A:
They would not be my first choice for framing stock. I have done quite a few frames and have sawn a few sycamore in my day. Qsaw the wood for flooring. If you intend to use the timbers for the frame, I would oversaw by several inches, then sticker. In a few months you will see which way it is twisting and resaw them square. They will bow and twist unless you got the best sickymore in the country. Short and fat timbers would not be as bad (12' or less).

From the original questioner:
Is anyone going to say anything good about this? :) The concerns brought up are the same ones I've had about the stability. The 4/4 and 5/4 is going to be qtrd, the beams will be 8x8 and 8x10, 12-16' long. I am hoping that the beams would stay fairly straight since not too much wood will be removed to square it up. Once I settle on the floor plan, I can figure exactly what sizes to use for the spans. Thanks for the comments.

From contributor D:
You were wondering it anyone was going to say anything good, so I will. Sycamore is beautiful. However, like many beautiful things, there is a price. You just have to be willing to do all the extra steps, saw oversize, re-saw, carefully grade the logs for straightness, put up with the waste, etc. Even if you do all those things, it might still break your heart. Quartersawing the 4/4 and 5/4 will help. What is left can be used as secondary wood in furniture, drawer sides, backs, etc. The flat sawn stuff just won't stand being glued up in panels. As beautiful as it is, there is a reason why you don't see much sycamore in general use. So if you have a love affair with sycamore, go for it. What you end up with will be beautiful and unique. If, however, your motive is convenience because it just happens to be there, you might have less suffering if you use another species.

From the original questioner:
Thanks. One option would be to oversize the beams to keep them more stable. For the real long ones, they could be sawn oversized, then sawn again after some drying. Can large beams be partially dried in a kiln?

From contributor K:
I would have some concerns about it being a favorite bug-candy. Don't even think about leaving any bark on it, for this reason.

From contributor R:
In the timber frame industry, it's typical that frames are cut and delivered with green or near green timbers. Sometimes a log may go from a growing tree to an erected structure in 6 weeks, maybe less. It takes so long to dry wood in a timber form that it's impractical and costly, not to mention it forces stress in the wood to react quicker, before you get a chance to join and assemble the frame. If you are hell bent on using these trees, try to join and assemble the structure as soon as possible after milling the timbers and be sure to select joinery methods that take advantage of the joint to help the timbers resist twisting.

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