Natural building materials
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Authors
Hall, Min
Drayton, A.
Drayton, A.
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Date
2024-06-14
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Conference Contribution - Oral Presentation
Ngā Upoko Tukutuku (Māori subject headings)
Keyword
New Zealand
building materials
domestic architecture
sun-dried bricks
rammed earth
straw bale houses
cob (building material)
low carbon
building materials
domestic architecture
sun-dried bricks
rammed earth
straw bale houses
cob (building material)
low carbon
ANZSRC Field of Research Code (2020)
Citation
Hall, M. (2024, June 14). Natural building materials [Paper presentation] Future Challenges New Zealand Institute of Building Inspectors Annual Conference 2024, Auckland, New Zealand.
https://hdl.handle.net/10652/6641
Abstract
The Earth Building Association of New Zealand (EBANZ) was set up to promote the use of earth and other natural building materials. EBANZ acts as a source of information on natural building methods and techniques especially for New Zealand conditions and as a network group for those interested in natural building here and overseas. Three of the more common natural building techniques include Mud or Adobe Brick, Rammed Earth, and Straw Bale. Presenters Min Hall from Unitec and Alan Drayton will discuss the design and construction techniques of the various natural building materials identifying issues that Building Inspectors need to be aware of when inspecting these types of properties.
MUDBRICK OR ADOBE EARTH BUILDINGS
Mud bricks, also known as adobe or just mudbrick, were made from a mixture of sand, clay, water, and frequently tempered with chopped straw and chaff branches. They were the most common method/material for constructing earthen buildings throughout the ancient Near East for millennia. Mud bricks are one of the oldest building materials in the world. They usually only require earth and the energy of the sun, so have very low embodied energy and environ mental impact.
RAMMED EARTH BUILDINGS
Rammed earth (or pisé) is an ancient technique that has been dated back to at least 7000 BC in Pakistan. It has been used in many structures around the world, most notably in parts of the Great Wall of China. Although most earth buildings are single or two-storied, a five-storey hotel was recently completed in Corralben, Australia.
Rammed earth walls are formed from soil that is just damp enough to hold together. The soil gets tamped between shutters with manual or pneumatic rammers. The mix is dry enough that once the material is rammed into place and a wall panel completed, the shuttering can be re moved immediately. One difficulty with the rammed earth method is that strict limits have to be placed on shrinkage to eliminate cracking. Sandy and gravelly material will have to be added to a lot of soils to reduce shrinkage. Often cement or hydrated lime is added to improve durability.
STRAW BALE
Straw bale houses were developed in America and are rising in popularity. They can be built with relative ease and speed, they may be load-bearing but more often they incorporate a post-and-beam frame with the bales being finished with a coat of plaster – often earth or lime based. The design issues are similar to earth buildings, but the need to avoid moisture and weathering is even more crucial. The construction detailing and plaster coatings make or break straw bale construction.
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