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

[john fordice]

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.
> 
> 
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