Clean, plentiful, and humble, earth has been a common building material for millennia. Earth-incorporating technologies in use in California include adobe, strawbale, rammed earth, and cob construction.

• Can have extremely low environmental impacts if the materials come from local sources
• Low-maintenance and likely to last - for centuries
• Require no toxic treatments, and do not outgas hazardous fumes; good for chemically-sensitive individuals
• Provide thermal mass, which helps keep indoor temperatures stable, particularly in the mild to warm climates of coastal California
• Biodegradable or reusable
• Can be easy to build with, requiring few special skills or tools
• Can be affordable to build with since the materials are inexpensive or free and the labor can include owner/builders, unskilled volunteers, friends, and family
• Unique, pleasant aesthetics
• Highly resistant to fire and insects
• Can be used for new construction, and (with planning) in additions and remodels as well

• May be more difficult to obtain necessary permits - but the necessary code recognition, structural testing, etc. is available
• Travel may be necessary for training
• With professional labor, building with earthen materials can cost just as much or even a little more than standard building methods
• Building with earthen materials tends to be labor intensive (although the necessary skill level can be low)
• Thermal mass acts to moderate swings in temperature, but optimal thermal performance typically still requires thermal insulation
• Concrete and rebar may be required for safety and durability

For thousands of years, people throughout the world have crafted cozy homes and communities with earthen materials. Earthen structures in China, Africa, and (chilly, damp) northern Europe provide excellent shelter after centuries of use. Earthen materials were a key element of American architectural vernacular. With scant timber but plentiful sod and straw, the Great Plains were home to sod homes, and also the cradle of strawbale construction technology. In the Southwest, adobe construction provided practical and effective protection from extreme summer heat and the chill of winter. One local example is the Adobe Santa Cruz Mission near downtown Santa Cruz, which survived both the 1906 and the 1989 earthquakes. Though the domestic popularity of earthen materials waned during the 20th century, a revival has taken root over the past thirty years.

By contrast, modern "stick-frame" construction has been standard practice in the U.S. only since the end of World War II and remains uncommon in many parts of the world. Standard U.S. construction practices require specialized skills and tools. By substituting earth for all or part of the wood, concrete, gypsum board (drywall), fiberglass, and other materials in a home, local and global environmental effects from the harvest, processing, transportation, and waste of these materials can be reduced substantially.

Provided they are obtained locally, earthen building materials can reduce or eliminate many of the environmental problems posed by standard building materials since they are plentiful, non-toxic, reusable, and biodegradable. Pollution of all types is reduced (or potentially eliminated by the rugged souls who do all labor by hand). Though they can be labor intensive, well-built earth-incorporating buildings last indefinitely with little maintenance.