Plywood Sheathed Box Forms

Using two-by-fours for corner bracing works well, but any dimensional lumber will do. Install a solid plywood sheet on the bottom and four sides of the form. 5/8-inch (1.5 cm) or %-inch (1.875 cm) plywood contributes to making a sturdy form with ample shear strength. The top of the form can be open-spaced boards. Be sure to install adequate blocking inside the boxes to prevent distortion from ramming the bags up against them during construction. Cut out handholds for removing the forms (Fig. A.21).

2" x 4" corner braces

2" x 4" corner braces

internal blocking solid plywood for shear-strength internal blocking

A-21

solid plywood for shear-strength

A split-box form is built in two halves with wedges placed in between them for easy removal from a finished wall.

Constructing them is still the same as the above-described process (Fig. A.22). Build them in even foot measurements for simplicity and reusability. Various dimension wedges can be used in between to accommodate odd width window and door sizes.

A full size, mineshaft style door form can be constructed using two sets of four-by-four posts framed with two-by-fours at top and bottom, and sheathed on either side with plywood. This type of form can be dismantled after the wall reaches door height and reconstructed into an overhead lintel (Fig. A.23).

exterior plywood siding held inplace with compression only

A-23

exterior plywood siding held inplace with compression only

A-23

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