Don, I'm not one for exact dates, but square rule was developed in the early 1800's. Scribe work carried on for some decades, much like there are still people building with full 2x4's and boards in the midst of plywood etc. I'm not sure if some building practices actually stopped more that they slowed down to a trickle and than picked up again, for there are folks still practicing both forms today. As a connection, I have seen a barn/garage in my area which is balloon framed ext. wall system, with a mortice and tenon timbered interior built in the 1940's.
I would classify CG frames and top plate frames as just being different and dependent on the material at hand, and not advantageous over one or the other. What could be some of the advantages?
Purlins I have seen are mostly hewn and longer small stock and show the bark, passing over a couple of rafters at least. It was a simple use of material and easy to handle. They are fun and easy to hew and you can man handle them. Probably not worth the saws time. And possibly made by the farmer, who probably whittled his own axe handles. Tim
