Doorjambs, shelf attachments, electrical boxes, intersecting stud frame walls, lintels, rafters, and extended eaves for domes, all need to attach to something that anchors them into an earthbag wall. Velcro plates are simply a flat wooden plate from one-half to one-inch (1.25-2.5 cm) in thickness, about twelve to sixteen inches (30-40 cm) long, cut to the approximate width of the wall and nailed into the bags. A strip anchor (a term used in adobe construction) allows for the later attachment of doorjambs after the forms are removed. A strip anchor is a length of two-by-four or two-by-six attached to a Velcro plate. It is then placed with the two-inch (5 cm) side flush against the box form and Velcroed (nailed) into the rammed earth bag below with two-and-one-half (6.25 cm) to three-inch (7.5 cm) long galvanized nails (Fig. 2.29). The bag work continues over the top of the strip anchors, incorporating them into the wall system during construction (Fig. 2.30). Windows can also be attached to strip anchors or can be shimmed and set into the walls with plaster alone.
A type of modified strip anchor is used for the placement of electrical boxes, lintels for rectilinear window and door frames, cabinetry, shelving, and anything that needs to be securely attached to the finished walls. A Velcro plate is used by itself to help distribute the weight of an eave or rafter across multiple bags.
The advantage of earthbag building is its minimal use of lumber. Although a finished earthbag structure can have a lot of Velcro plates and strip anchors throughout, it is still substantially less wood than in conventional construction (Fig. 2.31).
2"x 4"or2"x 6" nailed to Velcro plate cross gn faces form cross gn faces form saw-cut end saw-cut end
5/8"- 1"board 12" - 16" long by 2/3 width of wall
Note: if wide boards are unavailable, use two narrower boards side by side — pallets are an excellent source for strip anchor materials
2.31: Anatomy of a strip anchor.
A "scab" is a Velcro plate used to connect a buttress into a wall or connect two rows of bags stacked side by side in a situation where this is more efficient than to stagger the bags in a mason-style running bond (Fig. 2.32).
If two-by-four lumber proves hard to scavenge, substitutions can be made with one-inch (2.5 cm)
dimensional lumber commonly found in discarded pallets. For the strip anchor as well as the Velcro plate, the cross-grain of the wood is stronger to screw into than the saw cut ends.
Have several precut Velcro plates and scrap two-by material on hand when you start a project so that when you come to a point in the construction where a strip anchor or Velcro plate is needed, the work won't have to wait while you measure and cut these necessary items. We will learn more about Velcro plates and where to use them throughout this book (Fig. 2.33).
2.32: As a buttress gets shorter near the top of a wall, it is simpler to interlock the bags with a "scab," rather than try to make two dinky bags fit.
^ nailing butt-ends scab scab
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