[Cob] opinion on foundation for cob

[howard at earthandstraw.com]

I've seen many buildings with concrete footings and rigid stemwalls fall down in earthquakes because their "legs" were knocked out from under them as their rigid stemwalls crumbled in the seismic wave.  Too many apparently have not learned the lesson's from FLLW about how to build with a rubble trench foundation which is what saved the Imperial Hotel from destruction in Tokyo when an earthquake leveled the rest of the city.   A rubble trench is put on undisturbed earth below the frost line, that is the point, and the oldest buildings in the world were not built like Phil suggests ...or they would never have made it to old.  America not only builds stupid it has a stupid healthcare system, a stupid justice system, a stupid monetary system, as stupid schooling system and a really stupid food system as well.   America's entire convention today is stupidity.


Howard Switzer, Architect
668 Hurricane Creek Road
Linden, TN 37096
931-589-6513
www.earthandstraw.com
  ----- Original Message ----- 
  From: phil moulton 
  To: 'Tys Sniffen' ; coblist at deatech.com 
  Sent: Sunday, June 28, 2009 1:59 AM
  Subject: Re: [Cob] opinion on foundation for cob


  My big concern is just what the last poster said.
  Putting a gravel trench down means a unstable stem wall.
  Most here might say put in a "urbanite" and concrete stem wall over gravel.
  I just do not feel its stable enough. We are not talking about a stick frame
  wall but tons of material.
  I know there are those who feel I am not "green" and that's ok.
  Even if you let it settle for a few years and machine tamp it down its still
  gravel with a drain pipe in it.


  When we build it will be on solid ground with rebar and a solid concrete
  pour 18 inch wide and 2 feet high.
  It will start with a good solid footing of undisturbed earth. If that's 5
  inches down or 20 the undisturbed earth has been there and is nicely settled
  into its home.

  Putting a stem wall over a gravel drain trench WILL cause it to crack...
  Put your gravel drain trench OUTSIDE the perimeter of the stem wall so it
  deflects any water around the foundation. 

  Phil and lilpony

  -----Original Message-----
  From: coblist-bounces at deatech.com [mailto:coblist-bounces at deatech.com] On
  Behalf Of Tys Sniffen
  Sent: Saturday, June 27, 2009 9:23 PM
  To: coblist at deatech.com
  Subject: [Cob] opinion on foundation for cob

  Kristin,

   

  My opinion (worth everything you paid for it) would be close to what you're
  thinking.  If you've got a stable foundation (of any sort), get down below
  the topsoil and then build up a stem wall. BUT, I would also suggest going
  further down  (9 inches or so?) and a bit wider than your wall and making a
  gravel trench (with drainage tube) so that your stem  wall can 'float' on
  that.  Also, I'd suggest you get the stem wall up and let it dry totally,
  and ideally do any settling it was going to do before you put tons of cob on
  top of it. 

   

  About determining the stability of your area, you should look into some
  local geological history, and then just sit out in the spot and think it
  through. Look at the land as if you could imagine the area flowing like lava
  through time. Is there a dip below your building spot? Is there a crusty,
  breaking off cliff above it? Imagine what the earth in that area has been
  doing for the last 1000 years, and that's probably what will happen in the
  next 1000.

  Tys

   

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