[Cob] NZ standards

[Bernhard Masterson]

Hello Graeme,

.5% shrinkage seems reasonable, but I find that in practice I can build well with mixes that show shrinkage up to 1% in a test brick.  Building with higher shrinking cob works when one is building at a rate where the previous lift has had some time to dry and shrink but is still slightly plastic so the application of a new lift causes the previous to mushroom slightly.  The mushrooming action counters the shrinkage seen where drying cob can pull away from window bucks etc.  Would it make sense to address this in the New Zealand revision?

Also I am curious as to the status of the revision.  A couple of years ago I worked with some friends and turned in an application for load bearing cob walls to the city of Portland, Oregon (here in the U.S).  The city development office was interested but they were concerned about setting a less than ideal precedent and suggested we just wait to see what the NZ revision looked like.  Is there any sort of a working group that I could contact to stay up to date?

Thanks,

- Bernhard 



Get under a sustainable lifestyle umbrella, the carbon is going to hit the fan.

____________________________________http://www.bernhardmasterson.com

Natural building instruction and consultation

Date: Wed, 8 Oct 2014 10:08:19 +1300
From: Graeme North <graeme at ecodesign.co.nz>
To: Feile Butler <feile at mudandwood.com>
Cc: Coblist <coblist at deatech.com>, Pablo Loayza
	<info at naturallivingschool.com>
Subject: Re: [Cob] Alternative Materials Justification
Message-ID: <327DBA59-44BE-45E1-B4D5-986E023E13C7 at ecodesign.co.nz>
Content-Type: text/plain; charset=iso-8859-1
 
A small correction to the NZ standards reference
 
These do not specifically refer to cob apart from an informative sections but have been used many times to design cob buildings by making bricks and testing them to NZS 4298 as for adobe, with an additional shrinkage test thrown in. Cob was partially referred to in this manner as we were having trouble determining a reliable pre-construction test limit for cob shrinkage, but will be fully included in the revision currently under way. We are currently thinking about 0.5% over a standard 600mm long shrinkage box but any ideas on this welcome too.  
 
cheers
 
Graeme 
Graeme North Architects
49 Matthew Road
RD1
Warkworth 0981