Arch Window and Door Forms

Although we use a flexible form for our walls we use a rigid form to make the empty spaces for our windows and doorways (Fig. 2.22). This is the only place that requires a temporary support system during construction (domed roofs are self-supporting). The box forms

Earthbag Arch
2.22: Rigid form supporting door and window placement.

are leveled right on top of the wall. The bag work continues on either side of the form until the top is reached. The arch forms are then placed on top of the box form and leveled with wooden wedges inserted in between the arch and box forms. After the bag work of an arch is completed with the installation of the key-

2.23: Arch form being removed from the wall in the Bahamas.

stone bags, the wedges are knocked out, and the arch form is dropped down and removed (Fig. 2.23 & 2.24).

Box and arch forms need to be ruggedly built to withstand the rigors of rammed earth construction. The thickness of the walls and whether the roof will be a corbelled dome dictate the depth of the forms. The forms need to be deep enough to accommodate the bag work as the rows are "stepped in" to create a corbelled domed roof. Three feet (90 cm) deep is often a versatile depth for dome building. Forms for linear walls only need to be a couple of inches deeper than the walls to prevent the bags from wrapping around the edges of them (or else you'll never get them out). In some cases, individual plywood paneling can be placed alongside a too narrow form to extend its depth. Add one inch (2.5 cm) more extra width and height to the forms to account for the rough openings, depending on the type of window and door systems being installed. Sculpted concrete, lime-stabilized earth, brick or stone windowsills need several inches of extra height to provide plenty of slope. Consider the window sizes and customize the forms accordingly or vise-versa.

Availability of materials and preferred style of the forms (open or solid) are also factors to consider. For

2.24: After removal of forms. In curved walls, the columns in between the window openings take on an attractive trapezoidal shape.

2.24: After removal of forms. In curved walls, the columns in between the window openings take on an attractive trapezoidal shape.

traditional header style doors and windows, the open mine-shaft-style door forms can be made using three-quarter-inch (1.875 cm) plywood or comparable siding material and four-by-four-inch (10x10 cm) or six-by-six-inch (15x15 cm) lumber (Fig. 2.25). Once the desired height of the opening is achieved, the dismantled forms can become "lintels" (see Chapter 8).

Our favorite form system is a varying size set of split box forms and solid arch forms that can be used for dozens of structures (Fig. 2.26). One set of multiple size box and arch forms can be used to build an entire village of houses. They more than cover their initial costs in repeated use. Cinder blocks make handy forms for the rectilinear portions of the openings with wooden arch forms set on top. For the Bahamas Sand Castle project we had the delightful opportunity to borrow cinder blocks from our Bahamian friends who found the concept of "borrowing cement blocks to build a house" rather incredulous (Fig. 2.27).

To comply with FQSS approval, have all your window and door forms built for the structure before you begin construction. The structure is strongest built row by row with all of the forms in place, rather than pieced together in sections. It will save your sanity, stamina and time to go ahead and have enough forms built for the entire project from the start.

It is conceivable to infill bags with dry sand as a non-wood substitute for box and window forms. These sandbox bags can take the place of wood or cement blocks in delineating the rectilinear portion of doors and windows. Use a plumb line to keep the outside edges straight. Careful installation will be critical to maintain square. Allow extra room for error that can be filled in later with plaster around the window or doorjamb after construction. With a marking pen, denote where sandbox bags begin and regular earth-bags begin. Wrap chicken wire cradles around earthbags that butt up to sandbox bags to help delineate the difference. Remember to leave out the barbed wire on these sandbox bags or they won't come out later! (Fig 2.28).

2.25: An open, mine-shaft style form allows easy access to the inside of a building without climbing over the wall during construction.

2.28: Using sandbox bags as a substitute for rigid box forms.

for easy removal, face one rowof dry-fill sand bags out, tie or pin shut with a nail wedge arch form on top use chicken wire cradles to delineate between sandbox bags and regular ear-Mags

""Velcro" plate into tamped earth-bag with3" ggalvanized nails

2.29: Strip anchors provide an attachment for doorjambs and certain types of windows.

use chicken wire cradles to delineate between sandbox bags and regular ear-Mags

wedge arch form on top install additional sand bags lengthwise

""Velcro" plate into tamped earth-bag with3" ggalvanized nails

2.29: Strip anchors provide an attachment for doorjambs and certain types of windows.

2.30: Most doorjambs can be bolted to an adequate attachment surface that is provided by an average of four strip anchors spaced every three to four rows.

install additional sand bags lengthwise

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