Proponents: Martin Hammer, representing Martin Hammer, Architect (mfhammer@pacbell.net); john fordice, representing cob research institute
(otherfish@comcast.net); Michael Smith, representing Cob Research Institute (michael@strawclaywood.com); Art Ludwig, representing Oasis
Design (art@oasisdesign.net); David Eisenberg, representing DCAT (strawnet@gmail.com); Anthony Dente, representing Verdant Structural
Engineers (anthony@verdantstructural.com); David Rich, Reax Engineering Inc., representing Reax Engineering Inc. (rich@reaxengineering.com);
Kevin Donahue, representing Kevin Donahue Structural Engineer (kevin@verdantstructural.com); Ben Loescher, representing Self (bloescher@lmarchitectsinc.com)

Add new text as follows:
APPENDIX U
Cob Construction (Monolithic Adobe)
SECTION AU101
GENERAL

AU101.1 Scope. This appendix provides prescriptive and performance-based requirements for the use of natural cob as a building material.
Buildings using cob walls shall comply with this code except as otherwise stated in this appendix.

AU101.2 Intent. In addition to the intent described in Section R101.3, the purpose of this appendix is to establish minimum requirements for cob
structures that provide flexibility in the application of certain provisions of the code, to permit the use of site-sourced and local materials, and
innovative combinations of proven historical and modern techniques that are safe, reduce life-cycle impacts, and increase affordability.

AU101.3 Tests and empirical evidence. Tests for an alternative material, design or method of construction shall be in accordance with Section
R104.11.1, and the building official shall have the authority to consider evidence of a history of successful use in lieu of testing.

AU101.4 Cob wall systems. Cob wall systems include those shown in Figure AU101.4 and approved variations.

Clay subsoil for a cob mix shall be acceptable if the mix it produces meets the requirements of Section AU103.4.

 Sand or other aggregates such as, but not limited to, gravel, pumice and lava rock, when added to cob mixes, shall yield a mix that meets the requirements of Section AU103.4.

Straw for cob mixes shall be from wheat, rice, rye, barley or oat, or similar reinforcing fibers with similar performance. Before mixing, the straw or other reinforcing fibers shall be dry to the touch and free of visible decay.

 Cob mixes shall be of ny proportion of refined clay or clay subsoil, added sand (if any) and straw that produces a dried mix that passes the shrinkage test in accordance with Section AU103.4.1, complies with the compressive strength requirements of Section AU106.6 and complies with the modulus of rupture requirements of Section AU106.7.

Each proposed cob mix of different mix proportions shall be placed moist to completely fill a 24-inch by 3 1/2-inch by 3 1/2-inch (610 mm by 89 mm by 89 mm) wooden form on a plastic or paper slip sheet and dried to ambient moisture conditions, or oven dried. The total shrinkage of the length shall not exceed 1 inch (25 mm), as measured from the dried edges of the material to the insides of the form. Cracks in the sample > 1/16 inch (1.5 mm) shall first be closed manually. The shrinkage test shall be shown to the building official for approval before placement of the cob mix onto walls.

The clay subsoil, sand and straw for cob shall be thoroughly mixed by manual or mechanical means with water sufficient to produce a mix of a plastic consistency capable of bonding of successively placed layers or lifts.

Cob shall be installed on the wall in lifts of a height that supports itself with minimal slumping.

Each layer of cob shall be prevented from drying until the next layer is installed, to ensure bonding of successive layers. The top of each layer shall be kept moist and malleable with one or more of the following methods:

1. Covering with a material that prevents loss of or holds moisture,
2. Covering with a material that shades it from direct sun, or
3. Wetting.

When dry joints are unavoidable, the previous layer shall be wetted prior to application of the next layer.

Where holes to facilitate drying are used, such holes shall be of any depth and not exceeding 3/4-inch (19 mm) in diameter on the face of cob walls. Drying holes shall not be spaced closer than ten hole-diameters. Drying holes shall not be placed in braced wall panels. The design load on load-bearing walls with drying holes shall not exceed 90% of the allowable bearing capacity as determined in accordance with Section AU106.8. Drying holes shall be filled with cob before final inspection.

Roof and ceiling loads shall not be added until walls are sufficiently dry to support them without compressing.

MONOLITHIC ADOBE. Synonymous with cob.

NATURAL COB. Cob not containing admixtures such as Portland cement, lime, asphalt emulsion, or oil. Synonymous with unstabilized cob.

NONSTRUCTURAL WALL. Walls other than load-bearing walls or shear walls.

PLASTER. Clay, soil-cement, gypsum, lime, clay-lime, cement-lime, or cement plaster as described in Section AU104.

SHEAR WALL. A cob wall designed and constructed to resist in-plane lateral seismic and wind forces in accordance with Section AU106.11.
Synonymous with braced wall panel.

STABILIZED. Cob or other earthen material containing admixtures such as Portland cement, lime, asphalt emulsion, or oil, that are intended to help
limit water absorption, stabilize volume, increase strength, and increase durability.

STRUCTURAL WALL. A wall that meets the definition for a load-bearing wall or shear wall.

STRAW. The dry stems of cereal grains after the seed heads have been removed.

UNSTABILIZED. A Cob or other earthen material that does not contain admixtures such as Portland cement, lime, asphalt emulsion, or oil.