[Strawbale]Re: Some loadbearing compression ideas/questions

[Rene Dalmeijer]

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 at 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