[Cob] finding stats

[claysandstraw]

> -----Original Message-----
> From: Shannon Dealy [mailto:dealy at deatech.com]
> Sent: Thursday, May 24, 2007 12:40 AM
> To: claysandstraw
> Cc: coblist at deatech.com
> Subject: Re: [Cob] finding stats
>
>
> On Wed, 23 May 2007, claysandstraw wrote:
>
> [snip]
> > <snip: for structural calculations cob = adobe>
> >>
> >> While this may be fine for getting you past the code, it will
> in many if
> >> not most cases cause you to do things which are structurally
> > unnecessary.<snip>
> >
> > ...well the thing is that by the time your walls have enough
> mass you have
> > far far exceeded the structural requirements for either cob or
> adobe.  So if
> > the adobe standards are strong enough then why go any further for code
> > purposes?
>
> You missed the point, the adobe codes require that structural
> reinforcement be used which while it may be necessary for adobe to meet
> the structural requirements is not necessarily needed for cob to meet the
> structural code.
>
> >> [snip]
> >>> 1. structurally, bond beams are worth it
> >>
> >> I would say yes, if needed, in many cases where adobe needs
> it, cob would
> >> unquestionably not need it.
> >
> > ... I think "unquestionably" is a bit stong.  I can tell you
> based on my own
> > "shake the building test" that my cob columns were stonger
> after the bond
> > beam went on than before.  I'm not saying that the building would have
> > collapsed without a bond beam, I'm just saying it was clearly
> stonger once
> > the bond beam was on. Now it has been well argued that cob can
> form a bond
> > beam, from what I have seen this is true.  But 6" of concrete
> and steel will
> > always be stronger than 12" of cob... in extreme circumstances
> of roof load,
> > earthquakes etc. this *might* be an advisable compromise in the use of
> > concrete.
>
> Again, you missed the point, properly built cob IS unquestionably
> stronger
> than adobe, and therefore, there will be cases depending on structural
> needs (which are regional), where a cob wall would be sufficient without
> the bond beam where adobe would not.  I am in no way implying that a bond
> beam will not make it stronger, nor am I implying that a bond beam
> should not be used with cob (and I said so), but forcing everyone who
> builds with earth to use a bond beam just because one would be needed if
> the building was adobe, is a silly and unreasonable constraint.  The use
> of bond beams and other structural reinforcements should be based on the
> actual needs of the site and material used rather than blindly applying
> cement and steel to anything that looks like adobe.
>
> The point here is that cob is not adobe.  Will applying the adobe code to
> cob work?  Yes, however, you MAY incur unnecessary structural and
> environmental costs due to overbuilding for blindly applying a code
> written for a different material.
>

o.k. o.k. I am not disagreeing that cob ("properly built") is stronger than
adobe. But if I'm using cob I'm already most likely incurring "unnecessary
structural and environmental costs" becuase I'm trucking in 2/3 to 1/2 of my
building in the form of manufactured sand and straw.

My original point in equating cob and adobe was in the context of dealing
with building code people: why start a code conversation from scratch? I
say: just use existing data on a similar material, becuase all the standards
for adobe also work to demonstrate cob's viability to an otherwise clueless
building department.     Kindra