I stopped by the mill Saturday and had a good talk with the owner. He said he could do mixed hardwood lumber for a timber frame whenever I am ready. He said he can get cottonwood in any size I need. Any experience with cottonwood? He said his grandfather's barn when he was a kid was timberframed with cottonwood and it was over a hundred years old. He also does cottonwood live edge siding. If sealed, could it be used for exterior applications? He said it is just poplar wood.
My experience is just from woodworking. It is "fuzzy" on the surface rough sawed compared to other poplar and also has a strong odor until well dried. It also seems to be a bit softer and does rot very quickly if exposed to moisture. That's my limited experience.
Matt
stickframer
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I'm using cottonwood on a frame - it's not done yet but it seems to be working ok. Cottonwood is known for being unpredictable when it dries so have extra pieces ready. I would not use cottonwood where it will be exposed to moisture. I would not expect it to last long as siding.
Although historically that are some american barns that had Cottonwood timbers, it's not common. Cottomwood is not a typical choice of timberframers today. Cottomwood grows very big, but often has very large growth rings, is more likely to move as it dries, can shake... I would avoid it myself for timbers.
For siding, although in the poplar/aspen family, it's very different from Tulip poplar. I'd hate to see you put it up and then it twists and pulls nails as it dries. Maybe it it was dry first and you knew it was flat? I wouldn't think it would be much different for siding than pine. You wouldn't want it near the ground (where all barn siding tends to rot). I'm using an 18 inch stone veneer at the bottom of a frame to get the siding up.
I sided part of my shop with cottonwood as I had a bunch milled up and was in a hurry. I regretted it by the following spring. Even though it was quartersawn it cupped really badly and actually pulled away from the screws. I replaced most of it with hemlock and pine. The pine moved the least bit, as the shop is only four years old I can't tell you much on longevity.