Jan is right. I just looked at the picture of the CG barn I saw on the way down and it has common rafters! But keep in mind the roof was changed to a gambrel, my guess is around 1900+. It has the flying plate as part of the add-on. Crazy, maybe but a lot of years have passed and that leaves room for many variations, some of which we have lost.
Steve, I may have posting abilities soon. Its wicked frustrating not being able to. So to be a responsible poster I am going to do it.
Don the the English barn has principal rafters and common purlins, with lots of cobwebs. Tim
