[Strawbale] Re: Drilled Strawbales

Robert Tom ArchiLogic at yahoo...
Tue Jan 8 00:46:37 CET 2008

On Mon, 07 Jan 2008 17:54:39 -0500, powerstationman at gmail...  
<powerstationman at gmail...> wrote:

> I am trying to find any information concerning a video I once saw that
> showed an architect / builder building a two story strawbale house using
> bales that were drilled on site, with two each 4" holes that were later
> filled with concrete.


I am not familiar with the project of which you speak but I will say that  
it sounds like a Bad Idea.

Presumably the concrete was intended to stiffen the bale wall and perhaps  
function as load-bearing columns.

The concrete would have required steel reinforcing rod embedded simply to  
provide continuity across the many cold joints. The cold joints would be  
necessary because the concrete would have to be done in maximum 1.2 metre  
lifts. Concrete cannot be dropped from heights exceeding 1.2 m because it  
will cause it to separate and then it's no longer concrete.
Even if you could do it in 1.2 m lifts, the small 4" holes would make  
placing the concrete very difficult, and quite likely could not be  
accomplished satisfactorily for any more than two bale courses at a time.

Since reinforcing steel needs a minimum amount of clear cover, the steel  
would likely be placed at or very near to the centre of the 4" diameter  
mass -- ie at the neutral axis of the cross section where it contributes  
nothing to stiffness of the column ... hence a waste of high  
embodied-energy steel.

I seriously doubt that the straw bales "encapsulating" the concrete column  
would be considered to be providing any sort of lateral support to the  
concrete so one would have what is effectively a two-storey high,  
laterally-unsupported, 4" diameter column.

Even if the column were a structural steel section, its slenderness ratio  
would likely (without my doing any number-crunching to confirm) render it  
unsuitable  for any sort of structural task.

  Furthermore, the excessively slender column's location at the core of  
bales is also the least effective location for  any contribution to  
stiffening the bale wall. This is basic Engineering 001. So the exercise  
would be nothing but a waste of concrete (another high embodied-energy  
material) + a waste of the time, trouble and resources invested to  
accomplish it.

Good points ? I can't think of any.

Sorry to sound so negative but I really do think that it is *that* bad of  
an idea and one that should not even see the light of day.

=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at chaffY a h o o  dot  c a >
manually winnow the chaff from my edress in your reply

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