Feature from Environmental Building News
May 1, 1995
Sidebar: Table 3. Selected Requirements of Draft Prescriptive Standard for Structural and Non-Structural Straw-Bale Construction.
• Minimum wall thickness: 13” (330 mm).
• Minimum density of straw bales: 7.5 lb/ft
3 (120 kg/m
3).
• Maximum wall height: One story with unloaded bale portion of wall not to exceed 5.6 times the wall thickness.
• Maximum unsupported wall length: 15.7 times the wall thickness.
• Allowable load on bale walls: 550 lb/ft
2 (2,684 kg/m
2).
• Minimum height of foundation (stem) wall: 6” (150 mm) above grade.
• Structural anchoring to foundation: minimum
1⁄
2” (13 mm) diameter steel anchor bolts at intervals of 6’ (1.8 m) minimum connected to threaded rod to tie down top plate.
• Moisture barrier: one of several barrier materials between top of foundation and bottom of bale wall to block capillary moisture migration.
• For load-bearing walls, bales must be stacked flat with bales overlapping in successive courses; various options for pinning bales acceptable. For non-structural walls, bales may be stacked on edge.
• Roof plate: two double 2x6 or larger horizontal top plates located at inner and outer bale edges with cross-bracing.
• Wall openings for windows and doors: minimum of one full bale from an outside corner and framed to carry roof load (several options possible).
• Plaster/stucco: cement stucco reinforced with woven wire stucco netting or equivalent, secured through the wall.
< Return to Article
