[Strawbale] Re: Drilled Strawbales
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
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
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.
=== * ===
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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