Box and arch forms constructed from two-by lumber and boards are more laborious to build, but when built from discarded pallets, they can be constructed for almost nothing (Fig. A.28).
Box forms made this way should follow the same criteria as for plywood forms. They should be strong enough to resist the forces applied from compacting bags against them. They should also be diagonally braced to resist shear forces.
Dismantle pallets by sawing the nailed boards with a Sawsall, or pry them apart using a big wrecking (crow) bar. Making a template of the intended arch shape out of sturdy cardboard allows one to cut the desired shape of the form. The following are some examples of forms built with one-by and two-by dimensional lumber (Figs. A.29, A.30, A.31 & A.32).
use 3 trusses for long forms or just two for forms under 2' long
diagonal bracing, r bracing andy blocking
2"x 4" framing diagonal bracing, r bracing andy blocking
sheath with-1" x boards
230 EARTHBAG BUILDING
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