SB: Re: earthen plasters and gravity

["Robert W. Tom" <ArchiLogic@yahoo.ca>]

Ned (who thinks his name is "Nick" wrote:
>> we basically have a bunch of bare trusses.  We were looking at tacking some
>> type of lath (preferably wooden but we're open to whatever might work)to the
>> underside of the trusses and plastering over it.  We'll probably insulate
>> above it with cellulose.  

to which Beel responded:

>What I hear you saying is that you are trying to make a difficult job even
>more difficult than it already is.  To begin with, I seriously doubt that
>you would ever get enough strength out of earthen plastered metal lath to
>support the cellulose above.  And as for plastering it, let me say that I
>wouldn't undertake the job.  If you absolutely had to plaster it, it would
>be with something that would generate a lot more strength in that horizontal
>position such a cement based mix and even then I would guess that it would
>need further reinforcement every 2 feet or so with something that is
>perpendicular to the bottom of the trusses.  

I'm sitting here looking at an earth/straw plaster sample that Beel sent me
and am thinking that the material looks to be quite capable of supporting its own
dead weight and that of some cellulose insulation *IF* as mentioned the other day,
it is configured such that all of the material is put into compression (as in 
a vault or dome form).

As a wild-@$$ guesstimate, I'd say that the stuff weighs about 30 lbs/cu ft so
if one were to make the ceiling as a series of coffers, say 4' x 4'x 1.5" thick, 
(ie each section would weigh only about 60 lbs or so ?) I would THINK that it 
would be well within the capabilites of the material, in terms of compression 
resistance. (I'm going to try and weasel...  ahem, "find" an engineering student
to do some tests in order to quantify these speculations)

Obviously, one would be thinking more in terms of a ferro-cement analogy
instead of a stipple-toned, textured-ceiling on sheetrock analogy.

However, instead of a steel rebar and chicken wire armature as is used
for ferro-cement, perhaps one would substitute some sort of reed or bamboo 
for the rebar, and straw or hemp for the chicken wire.

--- * ---
Rob Tom
Kanata, Ontario, Canada
<FlotsamArchiLogic@yahoo.ca>
(jettison the flotsam before responding)

Please visit http://www.theHungerSite.com daily



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