[Strawbale] concrete footings

[Mark Bigland-Pritchard <mark@lowenergydesign...>]

Hi folks.

I'm organising the building of a small (30 m2) sb structure this spring, 
on an environmentally sensitive site.  We need to minimise the amount of 
concrete going into the ground (to minimise embodied energy, to minimise 
local ecological impact through changed soil chemistry, and to minimise 
transportation costs).  So I've ruled out a concrete pad.  A rubble 
trench foundation is ruled out because there is no suitable rubble 
locally.  I'm therefore looking at some sort of pile foundation.  
Treated timber below ground level wouldn't meet the ecological criteria 
set by the site managers, and I don't want to take the risk with 
untreated timber; my previous experience of using boulders is that it's 
not the best way to do this because the timbers on top of them have to 
be individually shaped to fit (time-consuming, and not suitable for the 
mostly unskilled volunteer labour which we will have).  So I'm looking 
at using concrete piles, probably arranged in something like a 2m grid, 
to support the building.

My question is this: does anyone have experience they are willing to 
share of using proprietary systems for shaping the concrete such as that 
at www.bigfootsystems.com ?  (Bigfoot make a bell-shaped footing out of 
recycled plastic, into which the concrete may be poured.)

My second, more tenative question is:  can this sort of system be used 
with rammed earth instead of concrete?  (I don't think I have the time 
to learn everything I'd need to know to do this this time round, but it 
would be good to know what's possible for future work.)

atb,
Mark
Borden, SK, Canada