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[Strawbale]Re: Some loadbearing compression ideas/questions

Riki,
You should think more often you come up with very good questions some of which I cannot answer for myself. I will venture to answer your questions to hopefully start a debate. 

On Apr 28, 2005, at 07:36, strawbale-request@amper....muni.cz wrote:


Some thoughts about compression for you tecnical people.  I have been
thinking about these techiniques that are popping up as ways to reduce
compression on loadbearing walls. Specifically the techniques like those used by Tom Rijven, or the man in ávila: they use clay paster on the walls 
before or during the wall-raising.
I am a strong supporter of Tom Rijven's 'French dip' for some of the same reasons you mention but also because of instant fire and weather protection. It is also a very good way to make substandard (low densitity) bales more buildable, they become more stable. 
<snipped>
etc. SOunds good, huh? But the other day I was thinking (I do that once in 
a while) and I thought to question:  A compressed wall is sure to be
stronger, no? it may be more comfortable avoiding compression, but will it 
not make the walls weaker and capable of bearing less weight?
It depends Pre compressing does not really make the walls stronger it just lessens the amount of creep (long term settling under load) High density bales are definitly stronger. They exhibit a higher E-modulas of elasticity which realy means that for the same load they deform less then low density bales. 


On my
load-bearing walls I have a clay-tile roof, I don´t know if I could
recommend putting a heavy roof on an "uncompressed" loadbearing wall . . .But in the testing people have done they say that the plaster bears more weight than the bales themselves, some maybe my doubts are irrelevant . . 
.What do you all think?
The plaster always ends up carrying most of the load it is simply much stiffer then the bales. Not precompressing means the walls will creep (settle) much more over time then without precompression. Pre-compression means you can build faster. I would aways go for precompressing. It is not such a bother I find and helps making the walls easier to finish because they are more stable. There is also much less changce of plaster cracking. With a tile roof I would always pre compress 4% of the total wall height as found out by John Zang. (based on un-French dipped bales) We should do new tests with dipped bales. 


Rene