[Strawbale] Re: Straw Bale Castle
derek at unm...
Tue Jul 29 20:34:29 CEST 2003
> We want to build a four-storey tower house castle. [snip]
> challenges are what makes life interesting and
> to succeed would be very noteworthy.
Chris and Beth,
I wish you best of luck. You have recognized the possibility of
spectacular failure. I am surprised that you are willing to bet such
a large amount of money on the project, at such long odds, but I am
often surprised by earthlings. Most of my comments may seem
negative, and I want you to understand that I offer them with the
hope that they will increase your chances for success.
Your lengthy discussion of techniques, plans, operations, risks and
drawbacks show that you have given this a lot of thought. However, I
find many of the "facts" included in your presentation to be
debatable, and a few to be wrong. Obviously, the risks go up when an
analysis is performed based on incorrect information. The risks also
go up with each untried element. It is hubris to believe that we can
anticipate all problems and design for them. The greater the number
of new ideas, the greater the risk. This is inevitable and
exponential. The best we can do, with good planning, is to keep the
exponent fairly low. It is safer, and in my view, better, to
decrease the number of new ideas in a structure, when one is betting
My biggest concern is safety. You state that building at ground
level is a safety advantage. However, every bale will be laid with a
multi-ton structure hanging in mid-air, right above where the workers
are working. This suspended structure will become increasingly
heavy, tall, and unstable as building progresses. I see this as a
safety disadvantage. In relation to jacking a building, you say:
"Catastrophic failure is virtually unheard of." You detail your
plans for keeping people away from the structure during the jacking.
I commend you on that, but I am frightened that the workers will then
take up their stations, working next to and under this structure,
after each jacking step is complete.
I have heard of enough collapses of jacked and propped structures
that I would choose a different description of their
failure-frequency. The biggest risk is not that the building will
suddenly drop vertically, in column. I worry that it may buckle,
tilt, twist or rack, so that the walls do not remain in column. Wind
has tremendous force and leverage on a building, and during the
construction phase, the building will not be tied to the foundation
in the usual sense. I hope you have plans for many struts, guy
wires, braces and buttresses. These will increase the safety during
construction. When the building is complete, and the braces removed,
the integrity of a load-bearing strawbale building depends on the
strength of the stressed-skin panel, with the render layer providing
essential compression and tension functions. I am skeptical,
particularly during the long curing phase, that lime render can be
relied on. I would be skeptical of portland cement, too, lacking
detailed modeling of the forces involved.
I have questions on a few details, as well, but the above is probably
more than enough for one message.
Language Learning Center, MSC03-2100
Ortega Hall Rm 129, 1 University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm...
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