[Cob] How wide should a cob wall be in earthquake zones?

[Whidbey Island Soap Co.]

I can see having 2 ft or more thickness of wall but I dont know about the
rebar reinforcment in the walls. From all I've read about cob is that it is
very different in structure from Adobe or Super adobe. The nice thing about
cob is it has no mortar between any brick. Its just one big homogeous wall
held together by clay sand and straw. I believe in California they did a
shake table test on a scale model of a cob house and it held up almost to a
9 pointer before structuraly falling apart. I believe one book I was reading
said the straw acts as the binder in these wall and create a lot of lateral
shake stabilaty in the walls. I beleive Ianato and a few others have done
some research on it but still waiting to get their book through the library.

I will not be making my wall any taller than 8 ft. The buildings will be
single story and no larger than 200 square ft. I plan on making about three
structures one a living/kitchen/dining area one a bath house and one a
bedroom conected by breezways. building will be no more than 6 ft apart. I'm
going for curving walls and a very organic look.

I'm thinking of buying a cement mixer then puting up a small shed to protect
it and other tools from the elements before I begin the project. Any
sugestions on which type to purchase? I would like to do most of the cob
mixing in the cement mixer along with mixing clay plasters later in the
project. Eventually I woiuld like to surround the whole structure in a cob
wall to make a nice cozy courtyard with the rear sides of the building being
connected to the courtyard wall. Think of an african Kraal and you may be
able to picture about what I want to do.

Question though, can a concrete footing be poured in phases or does it need
to be poured all at once? I would like to do this myself but could hire a
cement truck if necesary to come to the property.

I'm prety much on my own building the structure. Any sugestions on how to
get help in building it?

I am also thinking of erectin the roof structure first and building the
walls up to it. I'm looking at this as a long term project and hope that
having the permanent roof on the buildings will alow me to work through the
winter. Does not get to cold here so not to woried about it.

Thanks again!

David T
-----Original Message-----
From: coblist-bounces at deatech.com [mailto:coblist-bounces at deatech.com]On
Behalf Of john fordice
Sent: Friday, June 16, 2006 12:43 PM
To: Whidbey Island Soap Co.; coblist at deatech.com
Subject: Re: [Cob] How wide should a cob wall be in earthquake zones?


David & All,
Here are some SEISMIC STABILIZATION STANDARDS.  I've developed these based
on some shaketable tested methods for adobe construction & they are very
easy to include in Cob.

Feel free to extend the dialog if you wish.

john fordice - cob architect / builder

...............
WALL HEIGHT / WIDTH / LENGTH & OPENINGS   - when designing walls & placing
window and door openings in the cob follow these criteria:
cob wall height to thickness ratio of 7 : 1
 taper 7:1 thickness to 12² wide at top - reduces upper weight of the wall
buttress or thicken all open ends of cob walls to at least 2x the wall
thickness
maximum opening : wall length ratio of 1 : 3
3¹ feet minimum from a corner to openings
2¹ minimum wall between openings
4¹ maximum opening width
 wall shorter than 3¹ in length should not carry any structural  loads from
above
no concentrated beam loads into cob walls - distribute all loads

EARTHQUAKE DESIGN - cob can be built to survive earthquakes - some basic
earthquake design principals are:
a continuous reinforced concrete perimeter footing - 12³ deep x 18² wide
minimum - minimum of 2 #4 horizontal rebar - - wider  with 3 #4 for walls
over 8¹ tall
a  mortared stone or Urbanite base wall - 16² minimum height above finished
exterior ground - match cob wall thickness
3/8² SMOOTH rebar vertical ties at 24² spacing in full height wall sections
- embed in footing & hooked to a #4 cross bar in footing - full height of
wall - attach to bond beam atop wall - thread top 6²
cob wall height to thickness ratio of 7 : 1 - taper walls to 12² wide at top
to reduce upper weight of the wall
double 2x4  bond beam embedded in top of wall - vertical tie rod at  lapped
corners  - stud 3 sides in wall w/ 16d nails at 3²-4² spacing.
rafters at 24² spacing max - nail well to bond beam ( angle clips preferable
) - solid block rafters at bond beam
plywood or 1² roof sheathing - well nailed to create solid roof diaphragm
assure continuity of connection between ALL structural components -
VERY IMPORTANT !!!


on 6/16/06 10:46 AM, Whidbey Island Soap Co. at Soap at whidbey.com wrote:

> Hi everyone!
>
> I am going to be building a small home here in Washington State and would
> like to know how wide I should build the walls of a cob house in an
> earthquake zone. Also is there anytype of reinforcing I should be looking
> into? Someone here mentioned building the walls two and a half feet thick
at
> the base and tapering them to the top for load bearing walls. How about if
I
> support the roof with post and beam construction?
>
> Thanks again!
>
> David T.
>
>
> _______________________________________________
> Coblist mailing list
> Coblist at deatech.com
> http://www.deatech.com/mailman/listinfo/coblist


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