[Strawbale] Re: Straw Bale Castle

Derek Roff 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 
people's lives.

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.

Best wishes,


Derek Roff
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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