Cob is a material in a family of the oldest and most widely implemented building systems found throughout human history.
A mix of clay-rich subsoil, sand, and straw, this simple mixture of elements yields a material which, when stacked upon itself, forms a wall which is fireproof, seismically sound, mold and rot-resistant, and comparable in strength to concrete. Its applications are wide and varied; it can be used as infill material in conventional construction or as a plaster-like layer over strawbale walls, it can be built and sculpted into furniture, fireplaces, shelving, and cabinetry, and it is often employed as a standalone material in the construction of entire walls.
The term cob is in common use in the United States due to the work of Ianto Evans, Linda Smiley and Michael G. Smith of the Cob Cottage Company in Coqueville, Oregon. It is a Welsh term synonymous with dozens of other building systems in the world. Equivalent terms exist for adobe, made by Indigenous peoples of what’s currently the Southwestern United States, banco, made by Indigenous peoples living south of the Saraha Desert (including current-day Senegal and Mali), Romanian chirpici, and Japanese arakabe.
Thanks in part to the research and advocacy of the Cob Research Institute in Berkley California, the 2021 International Residential Code contains an appendix approving cob for use as a load-bearing wall system in single story residential structures. This paves the way for a resurgence of the oldest building material in human history – one which has thousand-year histories in structures such as the Japanese Kura earthen storehouse, the adobe structures of the Taos Pueblo, and the mud-brick skyscrapers of Shibam, Yemen.
The arch design and construction was led by Ross Brubeck of the Woods Edge Builders Collective.
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