Terminology

• Stabilized adobe: water-resistant adobe made with admixtures added during manufacture
• Unstabilized (natural) adobe: adobe that does not meet the stabilized absorption test
• Burned adobe: mud adobe bricks cured by low-temperature kiln firing
• Terron: cut sod brick, permitted where units are dry and design follows the code
• Compressed earth block (CEB): earth block pressed in a machine
• Rammed earth: earth compacted in forms
• Bond beam: continuous beam at the top of the wall that ties it together
• Lintel: member over an opening

Standards

Classes of adobe (example: New Mexico Earthen Building Materials Code, 14.7.4 NMAC)

• Stabilized: a dried 4 in. cube cut from a unit gains no more than 2.5 percent in weight after 7 days on a constantly water-saturated porous surface; exterior walls of stabilized mortar and adobe need no additional protection
• Unstabilized: does not meet the stabilized absorption test; not permitted within 4 in. of the finished floor grade
• Burned adobe: generally not dense enough to be frost-proof and may deteriorate in freeze-thaw cycles; exterior use is discouraged where daily freeze-thaw occurs
• Terron: permitted when units are dry and the wall conforms to the code
• Manufacturers certify that adobes meet the physical requirements of the adopted code

Code organization

• The same code sets out adobe, rammed earth, and compressed earth block construction, foundations, bond beams, lintels, weather-resistive barriers, lath and plaster, and parapets
• Earthen building codes are published by some jurisdictions

Materials

• Adobe blocks: earth blocks, stabilized or natural
• Mortar: mud or stabilized mortar
• Concrete or wood bond beams: concrete bond beams for rammed earth use 2,500 psi concrete with steel reinforcement; wood bond beams as approved
• Plaster and stucco: protective finishes over adobe

Detailing

• Keep the base dry: use stabilized adobe or waterproof units for the first 4 in. above finished floor
• Provide a continuous bond beam at the wall top
• Support lintels and openings per the earthen building code
• Provide foundations that keep water away from the wall
• Protect exterior faces with plaster or stabilized units as the local code requires

Uses

Specific uses

• Houses in dry climates
• Garden and boundary walls
• Historic restoration and repair

Pros and cons

Pros

• Stabilized adobe resists water absorption

Cons

• Water and freeze-thaw damage unprotected earth
• Unstabilized adobe is limited near floor grade

Manufacturing and cost

Construction

• Earth blocks are formed and dried; blocks are laid in mud or stabilized mortar with bond beams and lintels, then plastered

Sources

• Cornell Law School: N.M. Admin. Code 14.7.4.10, classes of adobe, https://www.law.cornell.edu/regulations/new-mexico/N-M-Admin-Code-SS-14.7.4.10
• Cornell Law School: 2021 New Mexico Earthen Building Materials Code, https://www.law.cornell.edu/regulations/new-mexico/title-14/chapter-7/part-4
• New Mexico State Records Center and Archives: 14.7.4 NMAC, https://www.srca.nm.gov/parts/title14/14.007.0004.html
• Justia: N.M. Admin. Code 14.7.4.17 bond beams, https://regulations.justia.com/states/new-mexico/title-14/chapter-7/part-4/section-14-7-4-17