[Cob] length of straw and general research

[Shannon Dealy]

On Thu, 12 Mar 2009, Damon Howell wrote:

[snip]
> built). I'm not sure, but I would say the poor folks who built most
> of those cob houses in England didn't go to natural building school
> or do a lot of research into it. They simply dug the dirt up, mixed
> straw into it, and slapped it into a wall. What more is there to
> know? We seem to be so thirsty for the knowledge of how they did it
> back then that we're over analyzing a very simple idea: we can build
> our homes from dirt and it will last for generations as long as we
[snip]

While generally I agree with your sentiment, there are a few things to 
consider:

   - Traditional English cob was not built in a seismic zone, some of the
     modern ones are.

   - The straw they used would not have been chopped up which our modern
     machinery often does.

   - The straw they used was radically different from the straw we have
     today for the same crops.  All of our crops today have been bred for
     maximum grain yield, which as a side effect has made the stalks
     shorter and weaker (the more energy the plant puts into the stalk, the
     less it puts into the grain).  It may have had other effects as well
     such as possibly making the stalk smoother reducing the "tooth" and
     the clay's ability to grip the stalk.  Wheat straw traditionally could
     be used to make a 30 year thatched roof, modern wheat is to short
     and breaks down MUCH faster.

   - While they probably didn't spend a lot of time analyzing the soil and
     straw, they very likely learned many things passed down from previous
     generations which helped them to make a better building.  We don't
     have the benefit of all of this knowledge.

For stable ground in a non-seismic environment, you can probably get away 
with a lot, but that is not the environment in which everyone builds.

FWIW.

Shannon C. Dealy      |               DeaTech Research Inc.
dealy at deatech.com     |          - Custom Software Development -
Phone: (800) 467-5820 |          - Natural Building Instruction -
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