I have been investigating the history of a timber frame meeting house in Guilford Vermont for some time. It was originally constructed in 1788, then dismantled and reconstituted in the late 1830s. There is a brief history, some pictures and framing sketches posted here:

http://www.ltrr.arizona.edu/~cbaisan/Vermont/Guilford_Center_MH.pdf

The roof structure is rafters set in a ridgepole over queen post trusses. The trusses have a center timber hung from the top chord and set in the bottom chord in a dovetail mortise with a wedge. Is this truss style something that others have seen before and if so where?

My nephew who has some familiarity with such things has not seen it before - he at first assumed it (the central timber) had been added when the building was re-constituted to strengthen the truss, but it is in fact part of the original design.

Thanks for any feedback and apologies for my lack of familiarity with the proper terms of description.

CB

see:

http://www.tfguild.org/publications/kingposttrussTF72.pdf

Yes, thanks for the link TW, but there is nothing close pictured there. This is a traditional queen post arrangement with bottom chord, two uprights about 1/3 in, connected by a top chord - so the queen posts and the chords make a rectangle that is bisected by the central member. The sketch in the pdf I linked to shows the arrangement correctly except for the omission of angled braces in the upper corners of the rectangle.

I've been in the roof systems of a fair number of buildings here in Northern New England with Queen Post Trusses, (typ of public buildings) and I've not run across such a variation before.

I should think it would not behave well over time. Do you know if the Straining Beam (top chord) has deflected? Or is the Tie perhaps stiff enough that this failed to happen.

4 & a suggest that someone might have been trying to redirect load paths ?

Off topic - Do you know if those Knees are just wide thick molded plank, or if they're true knees?

I've puzzled over many such framing mysteries over the years, often the answer is elusive, though the search is always interesting.

Just solved one yesterday, a year long puzzle over some 150 yr old uncut layout. only the discovery of an advertisement seeking bidders, replete with specs, suggests the framer simply let a detail slip his mind, and then laid it out as specified.

As often as not, these little mysteries are like this example, rooted in human error

Sending you contact info for the person who might have your answer.

Thanks Will, that jives with my nephew's impression that it is an unusual layout. One of the trusses has the defect you suggest - deflection of the upper chord/straining beam. The lower chords are white pine - ~12"x12" x 45' with little or no wain. the queen posts and upper member and most of the bracing and the hewn rafters are oak (bit of yellow birch thrown in). Main posts also oak - gunstock style I think, but they are almost entirely obscured from view.

There was an oak timber plate that carried the rafters (mortised in) that was eliminated when the building was dismantled and moved. This lowered the roof and required that the queen posts be moved in ~18" and the upper chord shortened.

The roof has leaked and softened the pine timber around the old mortises on the out-of-square truss so perhaps water damage has weakened that one. Some repair has been engineered with lumber and bolts - not really to my liking and I am not sure how effective it has been.... well, it has withstood 220 years of weather and use and some periods of neglect and a move so perhaps one cannot say that the design was defective...

It is a little hard to believe it was a one-off design but perhaps it was... child of king and queen post.

Please explain what 'knees' you refer to as I don't know the terms. The original frame is mostly hewn timber with a few sawn braces, studs and joists - some or many of which are hemlock from the 1830s rebuild.

CB

Chris - I was asking after the solid braces joined to the Posts and the Ties / Bottom Chords, they are shown in white, and are perhaps boxed in and species and scantling was not identified so as not to disturb the trim?

This is interesting. Thanks for posting.

CHB, you said the pdf shows the truss "except for the omission of the angled braces in the rectangle"

Are you talking about angled braces from queen post to top chord? This is the only way that I could see to help with deflection of the bottom chord. Without something holding up the top chord in the "rectangle" it seems that the top and bottom chord would deflect equally given they have the same span (minus the load of the lath and plaster on the bottom chord). But if the builder was trying to diminish the deflection of the bottom chord so the ceiling would not sag, it seems you would have to prop the top chord (as close to the mysterious kingpost as possible) back to the queen posts. I guess this could keep the top chord from deflecting, and with strong joinery between "kingpost" and bottom chord keep the deflection to an acceptable minimum.

No engineer here, just a layman. Anybody else see plausibility in that? That is is, I am describing the omitted braces correctly.

P.S. The forum is acting a little quirky for me too, with posts across areas

Upon reflection I can explain the problem with the truss with the deflected straining beam - the original structure had no belfry. When it was rebuilt, a belfry was added and the gallery was reduced from three sides to one. We believe that some of the timbers that had been used in the gallery framing were re-purposed to construct the belfry, including a large pine timber that was cut to form two 'sleepers' that run from the end wall plate to the first truss and support most of its weight... with the logical consequence that that truss is significantly overburdened.

Will, sorry I don't quite follow you. You are referring to the sketch plan in the pdf showing ceiling joists etc? No members are intended to be shown in white so maybe the file isn't displaying correctly. I am working on a couple of revised sketches that I will post as .jpg files - maybe they will work better. (not sure how to place a jpg directly in the reply)

The ceiling joists are probably hemlock from the 1830s. The framing along the two sides (scantling? and braces) is mostly hardwood, probably oak, if I recall. I didn't sample that part of the structure and its a little dark and dusty so this is a guess although the braces are all hardwood where ever I took the time to check. The framing is all exposed in the attic space, but the walls and everything below ceiling level is encased in plaster, trim, and siding.

You mentioned previously you were going to refer me to someone?

You are most welcome Mo.

Yes, the braces are small relative to the rectangle though - I would say 'just typical corner braces' as my recollection. I am sorry I didn't spend the time to measure more of the elements on my last visit so I could answer more specifically. The queen posts are ~6' I guess and the top chord might be more than 15' in length - maybe 20' originally given that the building is 45' wide. It is a very stout oak timber and I think the braces just prevent rack in the rectangle rather than doing much about deflection of that timber. The rebuilders added hemlock braces (timbers) tying the queen posts to the bottom chord on the outboard sides on all the trusses. We don't believe any such framing was present in the original structure.

Chris