Just as it sounds, rammed earth is basically just soil compressed to about half it’s loosely packed bulk. It’s rock-hard and very strong and durable. Arizona building code requires it to have at least 3% cement mixed in as a stabilizer, yet another AZ rammed-earth pioneer, Neal Jones, feels so strongly that cement is unneeded that he built his own house without it. Cement is rarely added in Europe. Either way, if you walk up and touch it you’ll probably think it’s a lot like concrete. Insulated rammed earth (with several inches of rigid foam) is a good idea farther north, but probably not needed in southern Arizona.
A 30% clay—70% sand combo has proven reliable for raw rammed earth. Too much clay should not be used as the wall can shrink and crack. More than 40 percent of the world’s population uses earth as a building material.
In the past decade, cement stabilised rammed earth (4-10%) has become a popular building material in Australia and New Zealand
Rammed Earth Building. The Tidal Resonance Chamber, Tacoma, WA.
Local earths were slighlty colored with iron oxides to match the patina of the port. Using different oxides will color your walls. Designed by Robert Horner, 2010.
Depending on the amount of water used during the preparation, each layer can have a different aspect.
The Basics of Rammed Earth Building
Rammed Earth building, also known as taipa (Portuguese), tapial (Spanish), and pisé (de terre) (French), has been in use for millennia, the earliest surviving examples from 5000 BC in China.* Formerly time-consuming yet dirt cheap, today the technique can be as costly as stone in the hands of certain architects. For some big projects soils have been imported, large quanities of cement and insulation have been incorporated, and the expense of elaborate frame work and machinery can be sky high. Yet, if you have a nice 30% clay/70% sand soil on your building lot (or chalk, lime and gravel) and are good at constructing simple frames (or have access to prefabricated formwork), rammed earth building can be one of the most inexpensive and sustainable building methods on the planet. Whereas trees are being cut down by the thousands-of-acres-a-day, and cement is polluting to manufacture, soil is abundant and the earthiest of earth friendly.
Rammed Earth Walls
This termite-resistant, non-toxic, fireproof technique is also good to build walls, benches, supports, columns and thick blocks which can then be layered like bricks with a mud slurry between. Rammed earth using rebar, wood or bamboo reinforcement should be employed in earthquake prone areas. Although rammed earth has tremendous thermal mass and holds and releases heat slowly, it is not a good insulator. For colder climates, rammed earth walls can be insulated with a panel of recycled styrofoam. Rammed earth keeps interior humidity between 40 and 60 percent where walls containing clay are exposed to an internal space, the ideal range for asthma sufferers and for the storage of susceptible items such as books and artwork.
How Long Rammed Earth Building Takes
The process is time consuming and repetitious, but rewarding. And now with power tampers, the job is a bit less demanding. A newly tamped section of wall is so solid that, if desired, the forms can be removed immediately. If wire-brushing is needed after the forms are removed, to even out the framework edge imprints or to add texture, it must be done in the first hour after the form is removed, for the wall dries to the touch quickly, yet will not be fully dried throughout for months. Exposed walls may need to be sealed to prevent water damage if the walls will be exposed to heavy rain.
Down To Earth Building
Rammed Earth Builders, South Island New Zealand
Down to Earth Building (dte building) has been building rammed earth wineries, lodges, residential single and two storied homes and commercial premises in Central Otago since 1994.
The building of over 30 rammed earth premises in Central Otago makes Down to Earth Building one of the most experienced rammed earth companies in New Zealand.
By using locally sourced earth your rammed earth home will be eco-friendly and will bring you even closer to the environment you live in.
Earth building in Central Otago has stood the test of time. Homes built over 150 years ago are still being lived in today.
specs related to rammed dirt
Rammed earth will begin to cure immediately, and can take from several months to several years, depending on weather and humidity to complete the process.
5.4 Design Methods
Rammed earth walls have low tensile strength, and should be reinforced by providing a bond or collar beam. Beams can be constructed of concrete, wood or steel. Vertical reinforcing may also be done, and may be required by some building officials.
All openings in rammed earth walls, such as windows and doors, must have lintels to span the opening width. Water flow and moisture control is critical to protect structural walls. Special detailing to accommodate manufactured windows may be necessary to accommodate wall thickness. All openings for doors and windows will require a frame. Wood, as opposed to metal, is recommended due to the corrosive action of moisture from the soil material. Lintels can be concrete, stone or wood. Careful attention to both roof and opening details is necessary to protect the structure from water damage.
Foundations required by most codes are concrete reinforced with steel. Soil block material may be used as a filler material between piers of a reinforced concrete pier and beam foundation. Historically, many structures built with earth materials had no foundation, or used sand and gravel foundations. The latter are excavated trenches filled with two parts sand to three parts gravel. Trench bottoms should be graded to provide positive drainage. Soil material block should not be used in below grade walls unless supported on both sides. Natural moisture from the ground may infiltrate the block, resulting in reduced compressive strength.
Five associations of soils are derived from greywacke and they occupy most of the hilly and steep land of the district. The first-named soil of the association represents the hilly component, and the second-named its steep counterpart. Paremata-Terawhiti soils are grey powdery silt loams over yellow compact clay loams and clays. They are not as deep as the associated Porirua soils and contain weathering fragments of greywacke. Wind and sheet erosion have removed or truncated topsoils on many ridges. Moisture retention is low, soil structure is poor, and the subsoil is compacted. These soils occur in a zone 19 1.5–3 km wide around the Wellington coastline. Behind the coastal strip from Waikanae to Island Bay the upland soils become more brown, more friable and have smaller, distinctly developed aggregates (Fig. 6). These are the Korokoro-Makara soils which extend from Brooklyn through Newlands and along the Western Hutt hills to Moonshine Valley. Moisture conditions are much more consistent than in the coastal uplands. Soil erosion is limited to rare shallow slips unless pastures are over-grazed.