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Re: GSBN:Question regaarding toe-ups

Matts (and all) - First, let's hope that "...aridity reigns", not
"...aridity rains" (Is that an oxymoron... or just the Arizona desert
during monsoon season?)

This first idea may be too obvious, or have some obvious flaws I'm
missing late on a Sunday evening, but here goes...

With all the steps Matts' describes for the use of sawdust, it seems
like an awful lot of work, and the "support elements" might not be as
easy/cheap to find as hoped.  Furthermore, at this point, with the
"leakproof" RBA (?), and the building paper below the toe-up, it
seems the location of cellulosic material at this location is not of
great concern... So, why not just really solid 4" thick "flakes" of
straw as the filler?

Oriented with the "grain" of the straw parallel to the length of the
wall, each flake would be about 14.5" - 15.5" wide, and about 23"
long.  They should be able to be fit nice and tight between the
toe-ups, and if left a bit "proud" of the toe-up height (say 3.5" to
4" thick), they would compress just nicely to support the middle of
the bales, as the wall went up...  One other benefit would be that if
they are using "imbalers" on 24" centers or thereabouts, the flakes
should fit nicely between the rebar without having to skewer them
cross-grain over the pins.

A second possibility, though perhaps not the least expensive, would
be to use a wood-fiber based acoustic insulation board.  They sell
this stuff for about $7-$8 for a 4x8 sheet at the building supply
house, and it is treated with a fire-retardant (possibly borax) which
might help resisting decay.  It only comes in 1/2" and possibly 3/4"
thickness, but can be ripped on a table-saw very easily to make the
strips.  I'm not sure how easy it would be to skewer on imbalers, but
it is a more natural alternative to polystyrene.

A third option in this vein is a product called Tectum, which is a
rigid, lightweight, cellulosic ceiling panel material.  See
<<a  target="_blank" href="http://www.tectum.com";>http://www.tectum.com</a>> for info.  This would be a first for Tectum,
I'm sure, but it might make some sense.  The panels come in a variety
of thicknesses (for varying sound insulation uses), so it might be
possible to get it thick enough that you would only need two layers
to get to 3".  It should be able to be ripped to size very easily.
This material is typically coated with some kind of "finish" (paint,
sealer...?) as well as fire-retardants (it's typically used in large
commercial "lay-in" ceiling grids) that might make it less prone to
decay.  Finally, because it is so ubiquitous in commercial work, it
may be possible to find a 2nd-hand source for this, since it is taken
out of large commercial remodel projects by the dumpster load...
There might even be "recyclers" of this cast-off Tectum selling it
for lower-grade commercial or industrial uses...  Just a thought.

Hope one of these ideas stirs some more...

Tom Hahn

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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