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Re: Details, Struts, Thrust, Etc.

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Bill,
 
It's magical.
 
I'm sometimes in awe of the old framing I've seen: off-sets mid-length of hips, 2"x4" rafters spanning 16 feet,  perfectly fit rough-carpentry joinery.  I remember an attic of a 100+ year-old house in Riverside CA that I could have spent hours in for fun, looking at how the roof was framed; except it was an August afternoon.
 
The proof is not to be found on the calculation sheet or in a reasoned SE's lecture -- though I'm certain it could be done, if liveloads are minimized [think 3-D space-frame].  The proof is in the 50-year-old, 75-year-old, 100-year-old-plus houses that were built that way and stand.  You've got to see them.  I figure that the guys who built these houses were somehow mentally wired by experience or dna to intuitively understand where the forces went and what it took to provide structural stability.
 
Another remarkable class of wood construction is the single-wall house.  They were built on the west coast [probably other places too, but those places are out of my territory] in the 1800's and early 1900's.  Nearly every single wall house I've seen has beautiful, perfectly cut, well-fitted joinery; many have long spans, and roofs without collar ties.  It is a fact that many have sagging roofs and other distortions, but they survive wind storms, earthquakes, snow accumulations and time.  Commonly used methods and details seem to have been widely-spread in time and space.  But I've never been able to find anything is writing about the technology.  How did the system develop and get communicated so widely?
 
Nels Roselund
Structural Engineer
South San Gabriel, CA
njineer(--nospam--at)att.net
 
Bill Polhenus wrote:
>You have a house with a hipped roof. The house has an "ell" or two coming off the "main" part of the structure, and the roof heights are different because the slopes are the same, but the widths of each part of the building (in plan) are different.
 
I cannot figure out how to get such a configuration to "work" without a post at each end of the ridge beam. It just doesn't compute for me, especially when the pitch is rather shallow (30 deg. or less).
 
So, convince me that the thing doesn't collapse into the hallway of the main house.<