for historical reasons I am trying to gather as much info as I can about this 1866 School House I am renovating. I was hoping I could attach pics here but I can't so here goes, hopefull, a good description: I have a classic New England Style one-room school house built in 1866 in
Dalton, MA. Construction style is Plank-on-Frame.
During the current renovations I took out the original lath and plaster ceiling to expose a very intersting truss system. My inspections have concluded that this is a ceiling truss and not a roof truss. It is composed of 8x8 very Whaney, sawn timbers in a triangle with a 24' tie beam arcoss the bottom spanning the houses long plates, a 6.5' post going up perpendicular from the center (not connected to the roof and two equal length braces mortise/tenoned between the tie beam and post. this all makes roughly an upright 30-30-120 triangle. The most interesting features 1.: the post does not attach to the roof. 2.: the post/beam joint is fastened with a 16" long iron bolt placed up thru the beam and nutted inside a mortise in the post. 3.: the braces meet the tie beam aout a foot inside the tie beam/plate joint,; meaning no loading is transfered from the braces to the plate. The house is 32 feet long and there are two of these truss' dividing the house into 3 equal bays. The ceiling joists are a combination of drop in and fully housed tenons and only the center joist spanning between the truss's of each bay is pinned, to provide some longitudinal ties between the truss' and the gable ends I'd presume. From what I can see, this truss' job is to hold the ceiling from sagging as well as hold the walls from buckling out. This appears to be accomplished by the fact that the braces are in compression, the bolt is in tension and the ends of the tie beam are joined to the side plates of the house. If the beam tried to sag it would place the bolt in tension trying to pull the post down vertically and thus the braces would go into compression. I do have pics if anyone happens to be interested enough to see this. My only real question after all that is does this truss have a proper name and how common was its use? Thank you very much for your time.
[This message has been edited by shaun garvey (edited 02-28-2001).]