CONTINUITY OF TRADITION : NEW EARTH BUILDING
BEng., BCom., Registered Builder 3982
Committee Member JTC BD/83 - Joint Technical Committee of Standards Association of Australia and Standards New Zealand for preparation of a Standard for Earth Building for Australia and New Zealand
Executive Committee Member of the Earth Building Association of Australia
Ramtec Pty Ltd
PO Box 84
Western Australia 6911
Continuity of Tradition: New Earth
Modern earth building can be cost
effective and is widely used to build almost every imaginable style of building
from sheds, shops, studios and homes to commercial buildings, churches and taverns.
With increased awareness of the vast energy consumption needed to produce modern
non- traditional building materials, earth building looks set to increase
The rammed earth variety of new earth building, using earth as a structural load bearing material, allows a vast array of architectural surface textures and forms. The versatility of new earth built structures in terms of adaptability to suit varying topography and soil conditions is important. Characteristics such as fire resistance, thermal and sound insulative values increase the appeal of constructing with earth. The future for new earth building looks promising, with certain countries promoting initiatives to encourage new earth building.
Unfired earth building worldwide
Rammed earth building in Australia
Modern Earth Building is Alive and Well.
Modern earth building is alive and well over an enormous geographical area using numerous different methods of construction. Earth building, or unfired earth as it is often known, is being constructed at a growing rate worldwide. Methods of building in some areas are still the traditional methods. In other areas newer methods of earth building are evolving; mostly derived from traditional methods.
Earth buildings have served the worlds housing stock well in the past, and are presently serving well and can continue to do so into the future, forever.
Cost effectiveness of earth building techniques, be they traditional or newer, is essential to their widespread implementation. Cost effectiveness is measured against conventional or modern methods of building (not unfired earth) and compared to these, unfired earthen techniques can be extremely cost effective.
Whilst most forms of earth building
can boast excellent green credentials, human friendly earth wall buildings,
good thermal, acoustic and other properties, it is cost effectiveness compared
to other materials that moves earth buildings in to a position to compete strongly
with conventional buildings. This is happening both in Australia and elsewhere.
Many modern buildings constructed of unfired earth have this walling material chosen for strong environmental, aesthetic, performance and other reasons. In some locations where traditional earth building practices still continue there is a strong sense of using proven technology and repeating the successful lessons of the past.
The new earth building developments worldwide have generally taken the old traditional methods, extracted all the good aspects and added new methods to develop new technologies. The new technologies can give buildings with far increased performance than the old technologies. Such increases in performance may include vastly increased waterproofness, far greater durability, better strengths - be they compressive, tensile, shear and other; limitation of shrinkage (and shrinkage was often a problem in some of the older earth building techniques); at the same time retaining nearly all of the charm; being the colour, the texture, the physical form and the unique attractiveness of the old earth building techniques.
Whilst comparisons of newer earth building techniques to older earth building techniques can be made, it is more the comparison of all earth building techniques taken together, against conventional non earth building systems where positive outcomes in favour of earth will make earth buildings grow more rapidly in popularity (as a percentage of all buildings built, and in absolute numbers).
Cost is one of the main criteria in the building industry worldwide, so whilst generally acceptable performance must be provided, the overall cost of the building is very important.
To be widely accepted, any form of earth building must meet certain minimum requirements. In Australia the Building Code of Australia, which regulates all building, has two basic requirements for housing: that it is structurally sound and that it is weatherproof, as well as many secondary requirements relating to room numbers, room sizes, and so forth.
The common forms of earth building worldwide are, in the authors opinion of popularity, adobe block (mud brick), pressed earth brick, rammed earth, cob, poured earth.
Definitions of each of these methods are as follows (taken from Reference 1):
In Australia rammed earth buildings are growing in popularity in all areas. Rammed earth is commonly used in all styles of buildings from small buildings to luxury mansions. Western Australia leads the world in rammed earth technology and in the sheer volume of rammed earth buildings constructed in the last 20 years. Western Australia also boasts the biggest fired clay brickworks (on one site) in the world, which is listed in the Guinness Book of Records. Earth buildings have been successfully built in Australia and elsewhere, in deserts, near beachfronts, on flat slopes, on sloping sites, on sand sites, on clay sites, on rocky sites, on stable foundations and on reactive clay foundations and in nearly every climate imaginable.
In the USA adobe is commonly used for huge, luxurious houses. In both Australia and the USA the building owners have a wide choice from a bewildering array of conventional materials, but they choose earth above all else; they see earth as better.
To be increasingly successful, earth buildings must be seen by consumers as being superior to other methods of non earth building and areas of importance include:
The consumer must not see the results of the (inevitable) shrinkage. It is up to us, the practitioners, to take steps to eliminate it, lessen it or control it. This is widely done and generally with complete success.
The environmental benefits of earth building over non earth building are a major plus for unfired earth.
Unfired earth is the right material for a sustainable future.
Nearly all unfired earth building techniques have substantially less energy requirements for production than conventional fired clay bricks. To use the worlds fossil fuel supplies to produce fired clay bricks is a gross waste of embodied energy in to housing. Rammed earth has been calculated as using 1/700th of the energy in the ramming process compared to the energy used firing clay bricks of equal weight. Whilst aluminium may be thought of as "congealed electricity" so too can fired bricks be considered as "congealed energy". Adobe blocks, are puddled and naturally sun dried whereas fired clay bricks are generally kiln fired at high temperatures using large amounts of energy and most often producing big volumes of greenhouse gases and pollutants. Unfired earth building as an environmentally "green" building material is difficult to surpass.
Most earth building systems can be made stabilised or unstabilised. A stabiliser is an additive which improves the strength, durability or other properties of the walls. The most common stabilisers in Australia are: for rammed earth 6% cement; for adobes 3% bitumen; for pressed earth bricks 8% cement; for poured earth 12% cement.
Living and Environmental Benefits
As people are generally becoming more aware of the good feeling of living in an earth home, and taking note of the environmental benefits, so the popularity of earth building is increasing. Other benefits are that the natural earth can often be taken from the site where the house is to be built thereby also saving in transport costs, and giving a sense of "local identity".
From a comfort point of view, rammed earth buildings, in common with other earth buildings, stated by Professor Rogers of Melbourne University, Architecture Department, have a "much higher quality of space about them than the same space defined by conventional materials". This widely recognised benefit so capably described by Professor Rogers is the well known feeling of "wellness" or "good vibes" that so many occupants of earth buildings have described over the decades. Earth buildings have been described as low toxicity and allergy free. Earth walls have colour, texture and "feel appeal" that is rated highly desirable by most occupants. The tactile attractiveness of most earth walls is very widely accepted. It is no surprise that many building biologists worldwide often favour earth as a building material over other building materials. The sick building syndrome is not linked to earth buildings.
The Faraday Cage is notionally an electrical conducting surrounding box the size of a building which can generate electro magnetic fields, the so called EMF effect, which are unpleasant to humans. A steel box or steel framed house can generate low level electromagnetic effects as it sits on a site, as in reality it is moving through the earths weak magnetic field. Such effects are said to not exist with earth walls. The Faraday cage phenomenon is being studied by building biologists and those seeking the best living environment. Further and more decisive research is required in this area to clarify and quantity what is said to be a big advantage of earth buildings over conventional buildings.
Most forms of earth building can be recycled in all or in part. Well designed and constructed earth buildings are low maintenance.
In Australia rammed earth colours available are from pure white through all the earthen tones including reds, yellows, browns, oranges, pinks even through to grey and black. Rammed earth walls change colour dramatically as the sunlight changes through the day.
Textures available in rammed earth in Australia range from absolute smoothness through pebbly finishes to coarse rocky finishes to varying colours between the aggregates and the matrixes even to several different finishes provided in the one wall panel.
The thermal properties of earth walls are highly desirable, having a very high thermal mass at reasonable cost. The inhabitants of nearly all well designed earth buildings continue to be pleased with the comfort afforded by such buildings largely due to the high thermal mass evening out the day time/ night time temperature fluctuations. This effect is commonly known as the "Thermal Flywheel". Rammed earth has a good balance between thermal transfer (R-resistive) insulation (U Factor) and thermal storage (capacitive) insulation (Thermal Mass). A good balance of these properties is required for year round comfort in a house. Earth has this balance whereas most other conventional building materials do not.
In Australia, rammed earth is probably the most cost effective form of thermal mass available in the entire building industry.
Whilst most earth walls have excellent appearance on both the outside and the inside of any home, it is the internal walls, the room dividing walls and such like, which provide the thermal mass (within the outer building envelope) to give lifelong comfort to the occupants.
In the internal walls, it is the thermal mass which determines the comfort of the home and insulation or R factor is, by and large irrelevant. Insulation or R factor slows the passage of heat though the walls but has little relevance in storing energy. Rammed earth has high mass, at generally above 2000kg/ cubic metre (and always above 1700kg/cubic metre) and a good specific heat which gives excellent thermal storage. Furthermore, all earth walls inside the house have the ability to re radiate either heat or cool with a delayed response when compared to outside conditions. Good design optimises this. Humans near a wall of high thermal mass receive a direct sensation of coolness or warmth regardless of the air temperature surrounding them. This is a pleasurable effect that has no operating cost and lasts forever.
The effect of heavy earth walls transferring energy to air is that they affect the air temperature a lot whilst changing their own temperature a little; this means that they are very effective.
Earth buildings, with their ability to breathe, can act as a moderator of humidity and they can lend themselves to inbuilt evaporative cooling applications. Earth walls can absorb moisture vapour and release it at a later time when its cooling effect can be of real benefit.
Ramtec has observed its rammed earth walls in a hot humid climate where the night time humidity is high from a coastal location, absorbing moisture in to the walls, which is then released during the heat of the following day, giving an enhanced cooling effect. This tends to make the buildings cooler in the heat of the day despite there being little difference between day time and night time outdoor temperatures.
Whilst not as good as refrigerative air conditioning, it is a cooling effect sufficient to give thick walled earthen houses a reputation for extremely comfortable living in harsh climates. Of course, in desert conditions or areas of high day time/ night time temperature fluctuations thick earthen walls of any type are excellent thermal moderators. This is one of the major reasons for the historical widespread use of thick wall earthen buildings in areas of high daily temperature fluctuation; to give lasting comfort to the occupants due to thermal lag and decrement.
The technique of thermal coupling by connecting the building in to the core earth temperature just below ground level by concrete slab on the ground or earth floors on the ground needs to be more widely encompassed. The thermal analysis of this very satisfactory arrangement needs to be more readily available. Methods of building better earth floors need to be developed and publicised. How to get rammed earth floors, which have many excellent attributes, more level and consistent needs to be researched. Improved construction methods are required.
Further work is required to make available clearer, more readily available computer programs to better predict the thermal performances of earthen buildings of various type in various climates. Account MUST be taken of the thermal mass benefits of thick earth wall buildings (capacitive insulation) and any thermal analysis should not be totally reliant on resistive insulation alone as measured by R factor or U value.
Resistive insulation (analogous to an electrical resistor which resists flow) reduces the rate at which heat is able to penetrate an element. Increased R value increases the elements resistance to heat flow.
Capacitive insulation(analogous to an electrical capacitor which stores electrical energy), which, as a consequence of the mass and specific heat of the element, both delays the penetration to its inner surface and reduces the magnitude of a change in heat flow, occasioned by an increase in temperature at the outer surface of the element - increased time lag.
In the USA full thermal analysis is required of all new houses piror to being issued with a building licence. Pacific Power and Gas sponsored and showcased a rammed earth wall house with 600mm thick walls due to its excellent thermal properties. It was built at 1058 Second Ave, Napa, California by David Easton and exceeded Californias stringent energy regulations by over 50%. (See reference 2)
In Australia, there is a requirement for minimum levels of wall insulation for new buildings in Victoria (one of Australias more southern and cold states) and Australian Capital Territory (the legislative seat of Australia) but no requirements for the rest of Australia.
By the end of the year 2001, it is predicted that all domestic buildings to be built in Australia will be required by law to achieve a certain level of thermal efficiency before the Building Permit or approval to construct a dwelling is issued.
Energy efficient building design requirements are contained in the Building Code of Australia (BCA) - 1996. This is a performance based building code, which has the flexibility to allow the use of any design strategy, provided the system can be proven to comply with the BCA Performance Requirement which is:
"A building must have an adequate level of thermal performance to ensure efficient use of energy for heating and cooling."
This is law for 2 of the 8 states of Australia.
To assist designers meet this requirement, the BCA describes 2 approaches (called deemed-to-satisfy provisions) that can be used:
The above methodologies have been developed to suit the conventional forms of construction, such as double fired clay brick, brick veneer and timber, and place a strong emphasis on controlling the heat flow to and from the building. It gives methods of improving performance by increasing R values of walls by adding insulation to cavities. This is not easily done in earth wall construction. In general it is not an appropriate analysis for thermal mass buildings. Development of better tools of analysis are required.
The acoustic properties of any wall can be broken down into reflected sound within a room and transmitted sound, through the walls of a room. As regards reflected sound, most earth walls do not have the unpleasant acoustic hardness of smooth hard faced , factory produced, board materials (similar to hard, smooth rendered fired clay brick walls) where the "echo" can be quite harsh on the human ear. The uneven surface of the earth wall diffuses sound reflection which is easier on the human ear. Additionally, earth walls can very effectively block the transmission of sound due to their density and their thickness. In Australia a 300mm thick rammed earth wall was tested in terms of acoustic transfer to Australian Standard 1276-1979 and gave a sound transmission class of 57 which is indeed a high achievement for any building material. It is notionally a loss of 57 decibels of sound energy stopped from passing though the wall.
A 300mm thick rammed earth wall, when tested to Australian Standard AS150.4 - 1985 - fire resistance test, gave a test result of 4 hours/ 4 hours/ 4 hours for structural adequacy/ integrity/ insulation which is a very high fire rating for any wall product used in domestic construction.
Mud brick walls have similarly been tested in Australia, totally successfully, for fire resistance.
There are well documented cases of old earth buildings in Australia having their roofs and fitments destroyed by fire, since major bushfires are fairly common in Australia, and the earth walls left standing undamaged and because they are too difficult to demolish, being simply used again as the solid basis for the rebuilding and refurbishing of the building.
The low energy consumed in the construction of earth buildings and the lower energy consumed over the life of the finished earth building can be of great benefit.
Bill Lawson (Reference 3) has looked at embodied energy and green building methods. His detailed book covers 11 case studies and of those using rammed earth, Ramtec played either a major part in their construction or built the walls in all the case studies. These include Bowali Visitor Information Centre and Park Headquarters at Kakadu National Park, Northern Territory(Case study 2), Kooralbyn Hotel Resort, Beaudesert, Queensland - a multi storey major project with more rammed earth in it than any other project ever built in Australia (Case study 3) and a holiday house at Dawesville in Western Australia (Case study 8).
Modern earth building techniques have in recent years been used to build almost every imaginable size, shape and style of building from garden walls, boundary fences, retaining walls, sheds, shops, studios, houses from the most humble cottage to the most luxurious mansions, through the full range of commercial buildings and churches, cathedrals, taverns, hotels, wineries, units, apartments, town houses, health centres, factories, garages, schools, kindergartens, universities, and others.
New earth buildings have been constructed in every imaginable situation in terms of climatic extreme, ground type and topography. In Australia, Ramtec Pty Ltd, from a base in Perth, Western Australia at latitude 32° south, has built over 500 rammed earth buildings throughout the length and breadth of Australia, from Darwin on the north coast at 12° south latitude to areas south of Melbourne at approx 38° south latitude. The total value of new earth buildings in Australia is estimated by the author to be in the tens of millions of Australian dollars per annum (A$1 is about 0.38 English pounds).
Australia is a large country with a large range of climates and earth buildings have been successfully built in all parts of Australia. There are many earth buildings in Australia as old as white settlement in Australia and many of them upward of 150 years old and still giving good service. These are quite young earth buildings by international standards. Worldwide, earth buildings have been successfully built in all parts of the world from right on the hot equator to the highest latitudes of the coldest countries, for centuries.
Worldwide, some earth buildings are load bearing and some are non load bearing, often depending on the local traditions. In Australia, nearly all rammed earth walls are load bearing and most adobe walls are non load bearing. The degree of earthquake activity worldwide where earth buildings have been built varies from not at all to extremely high level seismicity. The range of seismicity in Australia where earth buildings have been successfully constructed include those parts which are non seismic through to the most seismic areas of Australia which equate to the lowest levels of seismic activity in New Zealand. Earth building is in widespread use in New Zealand in the forms of adobe blocks (mud bricks), rammed earth, pressed earth bricks, and poured earth and some of these methods are extremely highly reinforced to meet the high level earthquake loading found in parts of New Zealand. All earth building in New Zealand is regulated by the "code". (Reference 1)
In parts of the world, modern earth building has risen to the challenge of high earthquake loadings with new developments including the sprayed earth technique developed in Californian to allow extremely high levels of steel reinforcing in a sprayed earthen matrix. David Eastons pneumatically impacted stabilised earth (pisé method) allows spraying of a cemented earth mix on to a reinforcing steel matrix which is designed to effectively carry the building though the worst of Californian earthquakes. (Reference 2)
Some of the major reasons for the popularity of earth buildings worldwide are the very pleasing colours and textures that are achievable together with the walls having a quite high thickness (due to the low inherent strength of unfired earthen materials) which gives the buildings a feeling of solidness and an intensely attractive appeal to their occupants. Common strengths of rammed earth walls in Australia are in the range of 2 to 4 MPA. Whilst higher strengths can be achieved, and often are, there is generally no need to achieve a strength greater than 1 MPA (1MPA is approx. 150psi).
The authors experience is in western countries where there is a wide choice of building methods and systems. In some poorer countries often the extreme low cost of earth makes it the only choice. In Australia, an extreme low cost of earth construction is only achieved by major unpaid input by the owner; the so called owner builder. Owner builders build more houses (from all materials, not just earth) than does the biggest single commercial house builder in Australia. Owner builders are a serious economic force and often choose to build in earth.
In Australia, the technique of adobe blocks is best suited to construction for owner builders with little money and a lot of free labour. The rammed earth technique requires a lot of expensive machinery and so is less suited to hands on "do it all yourself" type owner builders unless they are prepared for a lot of unpaid extremely heavy physical work such as is needed to form, mix, place and ram by hand. Non participating owner builders who subcontract out the various parts (trades) of the buildings to different specialist contractors very commonly build successful rammed earth buildings in Australia.
Some of the factors taken in to account in the decision making process to select earth for a chosen building project include the following:
Safety Aspects - a cyclone refuge
Thick wall earthen buildings, designed to resist cyclonic winds, also have the ability to resist penetration of cyclonic wind driven light, yet dangerous, flying debris. The building can become a refuge in a cyclone.
Overall, one must ask what price to put on lives and safety? Whilst all new buildings in coastal northern Australia must be designed to resist cyclonic winds in that the building must stay intact, there is no requirement that the building resist penetration by any flying debris. Rammed earth walls however, do offer a very high degree of resistance to flying lethal debris such as jagged corrugated iron roofing torn from upwind buildings.
It should be noted that hundreds of buildings from one to three storeys in height in Darwin built from locally produced cement stabilised pressed earth bricks did safely withstand Cyclone Tracey in Darwin in 1975, which had wind speeds well in excess of 200kms/hr (above 55m/sec).
Modern Earth Building Standards in Australia and New Zealand
Australia had an early earth building pioneer in the form of GF Middleton who worked for the Experimental Building Station, later to become the Commonwealth Scientific Industrial Research Organization (CSIRO) in Australia for many years who became an international expert in the construction of earthen buildings of all types. He published widely within Australia resulting in a wealth of knowledge, a Government body promoting earth building and a research organization able to provide valuable guidance in the execution of earth buildings. Upon his death, his work was maintained by CSIRO and Bulletin 5, ed. 4 "Earth Wall Construction" has been a significant official document in Australia. Earth building has therefore had the basis of a technical "semi approved" document for all of Australia for around 50 years and almost a "government endorsement" from a powerful government agency, the CSIRO.
Standards Australia with Standards New Zealand undertook to prepare a standard document to regulate all earth building in Australia and New Zealand. A joint technical committee (JTC BD/83) was formed to prepare a joint Australian New Zealand Earth Building Standard with the writer one of the committee members. When nearing completion the joint agreement process broke down when it became clear that the highly regulated building framework which is the cornerstone of building in New Zealand would simply not be accepted in Australia, in that the culture of submitting to a high degree of regulation, so well accepted in New Zealand, would be unacceptable in Australia. Therefore the New Zealanders proceeded to publish (see Reference 1) whilst Australia ceased to proceed with the project. There is presently no standard in Australia to regulate earth building. Earth building is however, allowed in all states of Australia under the Building Code of Australia which in general terms, refers to Bulletin 5, Edition 4 of CSIRO.
At present, Standards Australia is preparing an Advisory Document which they expect to have published soon. It is titled "The Australian Earth Building Handbook" and is co-authored by Dr Peter Walker and Standards Australia. It will have no official status unless it becomes referenced in the Building Code of Australia, which may well occur.
The Earth Building Association of Australia (EBAA) of which the writer was a founding executive committee member, and is still an executive committee member, is preparing a document to promote earth building in Australia which it hopes to publish in due course. It is titled "EBAA Earth Building Book". It is still being finalised and is expected to be available as a draft for comment by EBAA members within a few months. (Reference 4)
There are numerous standards and codes both in place and under development to regulate earth buildings in many countries.
This keynote speech was delivered at Terra 2000 Conference, Torquay, England in May 2000 by
Ramtec Pty Ltd
PO Box 84
Cottesloe, Western Australia 6911
Phone (08) 93845777
Fax (08) 93851308
1 New Zealand Earth Building "Code" comprises the following three standards, all available from
Standards New Zealand
Private Bag 2439
NZS4297: 1998 Engineering Design
of Earth Buildings
NZS4298: 1998 Materials and Workmanship for Earth Buildings
NZS4299: 1998 Earth Buildings Not Requiring Specific Design
2 The Rammed Earth House (1996), by David C. Easton
3 Building Materials, Energy and the Environment - Towards Ecologically Sustainable Development by Bill Lawson, Solarch, School of Architecture, University of New South Wales, Australia
4 EBAA -Earth Building Book, Earth Building Association of Australia
Mr Peter Greed - Chairman
PO Box 5055
Mildura 3502, Victoria, Australia