Having Confidence in Unfired Earth Structures

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Thursday, October 6th, 2016
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Architects, designers, certifiers, builders and clients all need to consider what materials they are specifying in buildings. They must consider potential hazards, nuisance and warranty as well as sustainable, energy efficient, desirable, safe and healthy choices.

Issues such asa age and neglect, flood, warranty claim, fire, termites, insect attack and weathering must all be taken into account. Bushfires, earthquakes and other disasters are also concerns.  How does unfired earth building stack up in some of these areas?

Earth building has some real trump cards when examined in several areas, some weaknesses that can be strengthened, and some problems that can be avoided. Overall, though, it is a great performer in many areas and regulators should value this. Insurance premiums should be reduced in many circumstances, clients should be delighted, builders and certifiers reassured, and architects and designers pleased with the results and performance.

The effects of climate change have become increasingly obvious. Flooding, storm damage, cyclones and bushfires are cause for serious consideration. Scarcity and cost of building materials has led to lower quality specification of materials and therefore issues with maintenance, longevity and end of life concerns with reuse, economic recycling potential or landfill and toxic waste. An insulated and sealed approach to energy efficiency has lead to problems with interstitial condensation, and weatherproofing; both are hugely expensive problems.

architecture Whether providing a fire rated wall within buildings or building safely in bushfire prone areas, earth walls have always exceeded minimum requirements. Earth walls are non-combustible and standard walls have a four-hour  (240/240/240) fire rating. They comply with BAL FZ, the highest Bushfire Attack Level, Flame Zone.

I replaced the timber roof frame and roofing on an earth walled toilet block damaged by a fire lit by vandals. The earth walls were unaffected and saved the building from write off.  I have witnessed load-bearing mudbrick walls; the only remaining sound element in a home engulfed and destroyed in the devastating Victorian bushfires of 2009. Lower floors, upper floors, roof and windows were all replaced in the rebuilding process.

During these bushfires, a family and their neighbours and animals – including horses – all sheltered safely within earth walls for 40 minutes of the firestorm and escaped unscathed. A small roof fire, the result of ember attack and poor roof detailing, claimed the older building after all those taking refuge were saved. They watched, traumatised, in a blackened wasteland of total destruction as the non-earth components of the building slowly burned in eight hours. The situation for many others was far worse.

We are facing increased risk of bushfire. In the interest of sustainable city development, we are using planning measures to increase urban density. Sustainable masonry construction is a sound strategy.

Thermal mass earth walls provide naturally conditioned comfort. This not only ensures energy efficiency, it can also provide adaptive comfort conditions with reduced reliance on carbon intensive energy. High thermal mass buildings also cope with a warming climate and erratic weather patterns all consistent with climate change predictions. They provide comfort and safety in both planned and unplanned electricity outages during or as a consequence of disasters such as bushfire.

It’s true that termites build themselves earth nests. However, they don’t use the earth in earth walls because that earth is devoid of moisture. Timber elements in earth homes are vulnerable and need to be protected according to standards.

Watertight, non-porous weather resistance of earth walls allows single skin construction so there are no cavities for vermin and pests to breed and live. Earth walls that pass the CSIRO Accelerated Erosion test can be exposed externally though earth parapet walls, and exposed earth walls need careful attention to detail to avoid minor leaks in climates with high rainfall. Use ground separation and sensible eaves to avoid problems.

Australia is prone to cyclones, and earth buildings can easily comply with cyclonic load conditions. Earth walled buildings were amongst the few buildings that survived Cyclone Tracey in Darwin in 1974. The considerable strength and weight of earth walls withstand wall loadings and resist roof loss. Furthermore, they reduce light-weight debris and shield and protect occupants from flying debris.

We are fortunate to have a very low earthquake risk in Australia. However, earth buildings can be better designed for resistance in locations with more significant risk by complying with NZ Earth Building Standards. Through simple measures like minor reinforcement, detailing around openings, standard connection of walls to structural diaphragms, hold down and appropriate design earth buildings can be strengthened for earthquakes. It is more about design and detail than the material itself. This was comprehensively proven through testing on a low cost bamboo reinforced cob home in testing at UTS in 2008. In Canada and the US, modern rammed earth buildings meet the world’s most stringent earthquake codes.

Measures aimed at energy efficiency have led to significant problems with interstitial condensation within walls in buildings. This has caused billions of dollars damage to structural elements of buildings in Northern Europe, USA, NZ and Australia. This is not the case with earth walls.

Undetectable repairs are usually easily made with earth and damage is often limited to elements other than earth walls or floors. Plasterboard and timber linings and frame (not earth walls) can be damaged as a result of leaking roofs and water escape from burst and leaking pipes and water heaters.

The longevity, maintenance costs and end of life consideration of buildings will gradually make it onto the agenda in terms of sustainability. Some modern building materials have a limited life expectancy and furthermore pose problems with reuse or recycling in years to come. They sometimes become toxic landfill.

Earth has a proven track record in all areas of longevity, low maintenance and ease of reuse. Earth material is borrowed for the life of a building and can be relatively easily recycled indefinitely. Embodied energy figures for earth walling start as low as 5kWh/m3.

Noise and electromagnetic fields are more and more modern day concerns. Earth walls work extremely well in blocking both. The quiet of an earth home is a valuable quality often noted by occupants and visitors alike.

Earth walls are natural, non-toxic and no- allergenic, which is a huge plus and warrants consideration of building material specifiers with health conscious and well-informed clients. Earth walls don’t rot, corrode or decay, and if they pass the accelerated erosion test they are suited to external weather exposure use without protection. Simple measures outlined in EBAA’s Building with Earth Brick and Rammed Earth in Australia should be complied with.

In both the urban and rural context, earth walls offer a very safe and sound sustainable choice.

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