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GSBN:Question regaarding toe-ups

I recently spent some time on the phone with one of our friends at Red
Feather Development Group.   They have been using a toe-up design that involves
double 2 x 4's on the outside and double 2 x 6's on the inside, giving a total
height for the toe-up of 3 inches (7.6 cm.) and a gap between the outer and inner
elements of about 14 inches (about 35.5 cm.), when using 3-string bales.
They have been using custom-cut strips of rigid foam insulation board to fill
this gap, but would prefer to be using a method that would require less labor
and a material that would be less expensive, not petroleum based, derived more
locally and lower in embodied energy.   Because they are working in areas
characterized by very cold winters, they are also concerned about the insulation
value of the flller material.   For this reason, they are questioning the use of
pea gravel as the gap-filler.   We talked about volcanic pumice, but found
ourselves unthusiastic based on the damage done to the landscape during mining
process, and the lack of any regional source.

They build their box-beam roof-bearing-assembly (RBA) in a way that blocks
any water from getting down through to the top of the wall, should the roof
leak.   In view of this, it occurred to me that if they were willing to provide a
moisture barrier, like roofing felt, under the toe-up, it would be safe enough
to use something like sawdust to fill the gap.   To provide some support,
along the centerline of the gap, for the first course of bales, one might lay in
place some separate support elements.   These could be assembled from short
pieces of 2 x 4 scraps or from pieces cut from warped, unsellable 2 x 4's
donated by a friendly lumber yard.   With these in place, one would fill in around
these separate support elements with sawdust, and then put the first course of
bales into place.

They and I would appreciate any thoughts any of you might have about the
sawdust system described above and any suggestions for alternative solutions to
the problem.   Let your creative juices flow.   Just don't let any of those
juices drip on your bales.   Let cellulosic aridity reign!


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