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#7912 - 02/28/01 11:30 AM can anyone identify this truss?

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).]

#7913 - 02/28/01 02:20 PM Re: can anyone identify this truss?
Ken Hume Offline

Registered: 03/22/02
Posts: 934
Sounds like a king post truss.

Can you email me some photos to

I did a survey on a one room schoolhouse in Royalston, Mass. last February which was thought to date from the late 1800's and hence I am keen to see the typical roof truss construction that you uncovered.

Ken Hume
Looking back to see the way ahead !

#7914 - 12/29/01 09:08 PM Re: can anyone identify this truss?

Hello Shaun:
Just ran across your post about the truss, and from your description I would say that it is no doubt a bridge truss, and as yu suspect just holds the bottom chord from sagging.
I have run across this type of truss in an 1865 Lutheran church here in Ontario Canada. The truss in the church was fabricated very similar and stood independent of the rafters which towered over the trusses. The difference in the church truss though was that instead of a vertical centre post the centre of the ceiling cross girt was held steady and straight by a vertical 1.8" wrought iron rod. This building has stood for 136 years now and is still nice and straight. The peculiar thing is that the last truss near the front of the church also supports 1\2 the weight of the spire whicch rests on it, but it has been additional strengthened by adding heavier timbers
The Northern Hewer


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