Rammed Earth Houses A Naturally Green Alternative

  My friend decided to build a "green" designed home long before it was popular. On weekends I would travel with her to home sites where innovative architects put their green designs on display. By using green building materials, selecting build sites in urban areas, particularly in blighted neighborhoods, and making use of local labor, products and materials, these homes added value not just to the prospective owner's "bottom-line", they infused money and hope into communities badly in need of both to help rebuild decaying neighborhoods.A few of the design books she borrowed from the public library showed pictures of "rammed earth" homes so well integrated into the surrounding habitat they literally disappeared into the landscape. These intriguing images made an impression on me. Building a home that "merged" into its natural environment seemed like the ultimate green house.Now that I'm exploring green building designs and materials looking for the best option for the onewoman/onehouse project, I want to really ferret out the positive attributes of rammed earth homes.

  What is a "rammed earth house" The basic principle of constructing a rammed earth house is aptly described by its title "rammed earth". Natural soil is shoveled into pre-made frames or forms and super-compacted so that when the form is removed a solid, mass of soil is left behind. A new form is placed over the compacted earthen block and the process is repeated until the desired wall height is achieved. Typically damp earth is mixed with a combination of sand, gravel and clay (added as a stabilizer) to produce the proper soil mixture. In the past, animal blood and lime were used as the primary stabilizing agents for rammed earth. However, modern construction companies use cement, lime and asphalt emulsions as stabilizing agents instead.To improve the aesthetics of the finished walls, homeowners can add broken pieces of colored bottle and/or timber to the soil mixture. The walls can also be texturized as the building forms are removed (before the soil dries into a hard surface).Pneumatic rammers make the job of compressing the soil in the forms easier than doing it by hand; the finished blocks of earth, at least 300 mm thick (12 inches to 14 inches), will be capable of bearing heavy loads like brick and mortar homes.

  Re-bar, wood and bamboo re-enforcements are sometimes used to strengthen the rammed earth to prevent failures during earthquakes or heavy storms. Adding cement to the soil in clay poor regions will also strengthen the soil mixture; as will the addition of water repellant admix.If you're wondering about the durability of a structure built entirely out of compacted "dirt", you might be surprised to know many famous sites in antiquity were constructed using "rammed earth" and are still standing today-parts of the Great Wall of China were built using a rammed earth technique.Modern rammed earth homes also benefit from technological advancements that make it easier to understand the unique properties of super-compacted soil. In fact, improved design methods, the use of soil technology and more regulatory control by building officials make rammed earth houses a great "green" building option for consumers wanting affordable environmentally-friendly homes.Cost factorsAlthough my research suggests rammed earth construction costs are nearly the same as the cost for regular masonry home builds, there are additional factors that could impact the final price of the house:How far will the soil have to be transportedThe number of walls that must be built (economies of scale apply)How complicated is the home designThe height of the wallsIt is also important to address the placement of wiring and plumbing in the early stages of the home design to avoid expensive alterations once the build has started. After taking these additional cost factors into consideration, there are still significant savings in building a rammed earth house.

  For example, A rammed earth homeowner can expect to only spend 2/3rds of the cost of a wood frame home of equal size and dimensions.Green FeaturesThe thermal mass of rammed earth houses, like adobe, will keep a house cool in the summer and warm in the winter without reliance on heating and air conditioning units. This is an 'energy-saving' feature that will also save the homeowner money.Rammed earth houses are naturally sound-proofed, termite-resistant, fire-resistant and ultimately biodegradable. The wide availability of soil, the fact it is a sustainable resource and the removal or use of soil will result in minimal impact on the environment, makes rammed earth homes an excellent "green" building material; particularly in impoverished regions of the world.