Photo: RammedEarthWorks.com blog

Interested in building, architecture and small homes in 1991, I bought a book called New Compact House Designs. It was the result of a contest for architects and designers to design a home under 1250 square feet. It is the compilation of entries and winners. Even twenty years ago, there was an awareness of the need for smaller, more energy efficient homes.

One of my favorite homes in this book was the second place winner by Rammed Earth Works. It was a 1241 square foot passive and active solar home of earth and wood. The earthen walls were 2’ thick with ‘quiet, cozy seats in most windows, and niches and bookcases carved from the thick walls.’ The pitched roof had large overhangs for shade and to protect the walls.

From Rammed Earth Works:

‘Environmental responsibility and our commitment to appropriate technologies present us with these timeless materials, and timelessness leads to an architecture not pretentious, but essential.’

And:

‘Earth walls not only save on heating and cooling costs, but also on maintenance costs. Best of all, a well-built solid masonry house will last for centuries.’

That pretty much sums up rammed earth construction.

David Easton, owner of Rammed Earth Works, wrote a book that many rammed earth builders recommend for technical information, construction details and history. It is simply and aptly called The Rammed Earth House.

Origins of rammed earth houses

Rammed earth has been around for thousands of years. The Great Wall of China, which is over 2000 years old, is partially rammed earth, as are Hannibal’s watchtowers, which were built in 300 BC. Rammed earth construction has been found in Africa and Europe, some in France and Germany being over 400 years old.

The rammed earth section of the Great Wall of China (Photo:Doron)

In 1556, the Spaniards built a rammed earth home in St. Augustine, Florida, the oldest city in the US, and this home is still inhabited. In the 1700s, German immigrants began building with rammed earth in the eastern US. Rammed earth construction eventually found its way west to the desert southwest and California. It is well suited to the sunny, dry climate of the west, especially in passive solar homes. Rammed earth makes excellent thermal mass for heating and cooling. Having characteristics more like stone than earth makes it appropriate for wet climates as well.

Different from adobe and cob homes

Unlike adobe and cob, rammed earth uses just a bit of clay in the mixture. It is mostly gravel, sand and cement with a small percentage of clay. The final product resembles stone in the way it feels and in its strength. The striations even look like sandstone, but it has all the warmth of earth.

Green building benefits of rammed earth houses

Rammed earth has the sustainable benefits of other types of earthen building along with a few others of its own.

• Low embodied energy by using local materials – no transportation costs, no wood, fewer resources and energy used
• Energy efficient – thick walls keep interior temperature fluctuations to a minimum
• Excellent thermal mass for heating and cooling
• Acoustic properties absorb sound making a quiet home
• Blends in with natural surroundings
• Durable – strengthens as it cures
• Fireproof
• Insect resistant
• Needs no finish work on exterior or interior walls, reducing work time and eliminating maintenance
• Can be used below grade with waterproofing and drainage
• Dye can be added for a variety of colored walls or in different layers in one wall.

Rammed earth construction

Photo: bengarland

Forms for the walls are put up in sections with gaps left for windows and doors. Each section is filled with a 7-8” layer of the earth mixture, which is then tamped down to 4-5”. Another layer is added and tamped, and this is repeated to the desired height. The forms are removed the next day, and the walls strengthen over time.

The walls beneath the windows are completed next with the same process to the height of the bottom of the window. Lintels are placed at the tops of window and door openings. They can be exposed or hidden within the earth. Second stories can be added onto the first floor walls. Rammed earth is a very strong bearing wall.

A clear sealer can be used inside and out for protection and to enhance the beauty of the material. Paint, tile or plaster can be applied, but it’s not necessary. That’s a personal choice, but most rammed earth walls are left as is.

How to build your own rammed earth house

Building a rammed earth home can be a do-it-yourself project, but you should attend some workshops or work for a rammed earth builder for a season. Absolutely read David Easton’s book, The Rammed Earth House, mentioned above.

DIY projects are beneficial in that they save money by not having to hire a contractor, and you gain a sense of accomplishment and feel empowered. I have designed and built a home and a major remodel. They are not of earth, but I still feel good knowing each was an extension of myself via my creativity.

Owner built or not, a rammed earth house will give you decades of sustainable satisfaction and enjoyment.

Stay tuned for green building with earthen homes, pt. 4: Earthships