Hi, I own a 20x40 schoolhouse in upstate NY that has pretty badly sagging ceiling which I'd like to have fixed. The usual way to fix this I've seen is to jack from beneath and then install something on the ceiling joists to keep them level. My problem is that I can't really do this due to the way it was framed. I'm told this schoolhouse was built in the 1860's, and perhaps even earlier, and I'm unfamiliar with the way the ceiling was framed. Basically, instead of ceiling joists spanning the 20 feet and resting on the top plates, there are large logs about every 10 feet. These logs are notched, and the ceiling joists are installed perpendicular to them in the notches. Can you tell me what this framing method would be called, and what might be the best way to support these logs holding up my ceiling joists? Thanks.