Newly revised earth building standards help marry future solutions with traditional techniques

Sponsored for free access to build the right way

A set of three newly published standards - NZS 4298:2024 Materials and construction for earth buildings, NZS 4297:2024 Engineering design of earth buildings and NZS 4299:2024 Earth buildings not requiring specific engineering design - have been sponsored for free access by MBIE Building System Performance, the building regulator. 

Led by the Earth Building Association of New Zealand (EBANZ) with support from other interested industry stakeholders, the latest revisions better align the 2020 version with the building code. They help promote the use of earth in a variety of traditional wall techniques and cover mud brick or adobe, cob, pressed earth bricks, rammed earth, internal adobe veneers, earth floors, and earth or lime plasters. Informative guidelines for using allied natural building techniques, i.e. straw bale, and light earth that uses a fibrous clay mix within a timber framework, are also included.

Earth building makes sense

Chair of the committee that worked tirelessly behind the scenes on these standards was architect, former Chair of EBANZ, and dedicated eco-designer Graeme North. Graeme was a recipient of a NZ Order of Merit (MNZM) for services to architecture and natural building standards and has built an international reputation over 50 years for his design of natural buildings. Graeme explains the work behind the revisions:

‘Despite including methods that have been around for 10,000 years and with structures that have stood the test of time for hundreds of years, earth building had fallen out of fashion. I hope the standards encourage more designers, builders and engineers to use these time-honoured materials as they fit perfectly into a low carbon eco-conscious environment.

‘Earth buildings make perfect sense today. Their mass readily integrates with passive solar design, and a well-designed building can require little external inputs of energy other than the sun. Natural earthen materials moderate indoor humidity and temperature, and the Standards show how they can meet modern regulatory requirements for strength and durability.'

World leading standards

New Zealand’s suite of earth building standards are world leading.  There are none other that are as comprehensive or integrated as these, and American earth building standards refer to the New Zealand standards to cover earthquake design. Collectively the three New Zealand standards cover around 500 pages of information.

Traditional earth building is predominantly used in desert climates or areas with low seismicity or jurisdictions with poor building controls. However, they can be just as effective across many climates now that we know how to withstand both earthquakes and wind driven rain. 

In Aotearoa, Māori did not traditionally build earth walled buildings as such but did create thick earthen palisades for Pā which still dot the landscape, or they dug into the earth for storage pits or partially earth walled and earth floored whare. Early European settlers brought earth building techniques with them that are still used today and there are many well-known fine historic examples still standing such as Pompallier House in Russell (1841) in the Bay of Islands, built of rammed earth walls, or Broadgreen in Nelson (1855) that uses cob with lime rendering.

‘The standards could have a revolutionary impact on the building industry by providing confidence in the use of a wide range of natural materials,’ says Graeme. ‘The 1998 versions were cited as acceptable solutions, which the current versions now expand and update.  They cover easily taught techniques, and if you can make a cake, you can build an earth house, it’s much like following a recipe so can be very suitable for owner builders as well as professionals. 

‘The standards let you test and certify your own materials. Clay is abundant in most parts of New Zealand and some tests are really simple. One mud brick test is dropping it in a prescribed way and if it holds together, it’s robust enough to build with.

‘Earth materials can be used in very simple or very sophisticated buildings.  A lot of architects think earth building means rammed earth if they think of earth building at all, and although this, and mechanically pressed earth bricks, can work well, they are often cement stabilised, which is not so good in terms of embodied energy. I’m hoping these standards will encourage people to look at natural unstabilised mud bricks or cob, which can provide inherent structure, inner and outside lining, thermal mass, as well as insulation if the density is low enough. The standards now include innovative structural low-density adobe (SLA) (or mud brick), and cob SLC.  EBANZ has been developing and testing these materials for quite a period of time and there are great benefits from  using natural clay materials that gives improved thermal insulation and reduced seismic loads.

‘This means that the standards now cover natural building techniques and materials that range in density from rammed earth at 2200kg/m³ to mud brick at around 1600 kg/cub to SLA at half, that down to strawbale that can be as low as 90-100kg/m³. The earth building standards cover a wide range of materials and techniques and each has its place and application.’

A valuable tool in builders toolkits

Graeme stresses the importance for designers, builders, engineers and building consent officers to use these standards as a really good resource in their tool kit. ‘These standards will also help with public awareness as anyone wanting to build an earth building may otherwise struggle to find expertise.

‘We’ve pushed these standards as far as we can take them for now and they contain the results of extensive research and testing criteria. Now I want to see designers use these low carbon materials as an important way to help reduce carbon emissions. 

‘Earth is a really good and viable material to use in the appropriate place and way and gives beautiful buildings while providing great acoustic and environmental properties. It’s non-toxic and moderates temperature and humidity, thereby acting as a natural air conditioner. Hotter humid environments like Auckland’s, can typically see 20% less humidity inside an earth building than outside.

‘I’m proud to say that buildings created to the 1998 standards – which were the inaugural earth building standards on which subsequent versions are based upon – have no recorded failure.'

Few earth builders are generalists but tend to cover one or two techniques, says Graeme. These standards together provide one set of rules based on the similarities for many methods of building with minor adjustments provided to suit each different techniques.

‘I feel that touching earth grounds you. When people go into a natural earth building something happens. There is a sense of wellbeing and pleasure that comes out of it.  People react to the acoustics, aesthetics, and the air quality when they experience these relatively simple materials.

‘I’d like to thank all the committee members, and their supportive nominating organisations, who have given thousands of hours of voluntary time over the years to contribute decades of knowledge to produce the 1998, 2020 and 2024 versions. 

‘Using these standards, and gaining from their contained learned experience, will help every architect, engineer and builder with the know-how to appropriately use a range of natural materials to produce buildings with local materials to suit their locale, and that can stand the test of time, be aesthetically beautiful, sensitive to the environment, and healthy to live and work in. Use them to make buildings of the future with tried and tested techniques of the past made modern.’

All three standards are available for free exclusively from Standards New Zealand.

NZS 4299:2024 Earth buildings not requiring specific engineering design(external link)

NZS 4298:2024 Materials and construction for earth buildings(external link)

NZS 4297:2024 Engineering design of earth buildings(external link)