How building codes save homes from cyclones, and how they don’t
GUEST OBSERVATION
During Queensland’s preparations for Severe Tropical Cyclone Ita earlier this year, Queensland Premier Campbell Newman advised residents who lived in older houses (those built before 1985) to evacuate their homes as they were not likely to stand up to the storm’s destructive winds.
In the event, the damage was largely to the electricity network, while Cooktown, very close to the path of the storm, suffered less destruction than had been feared.
But the episode still begs the question: what was so special about 1985?
That was the year that building regulations changed to require new houses in cyclone-prone areas to be able to withstand higher winds. But how were these regulations determined, what do they mean for modern homes, and why do regulators always seem to wait until after a severe storm before updating the codes?
Updating the regulations
Building codes are drawn up by the Australian Building Codes Board (ABCB), which cites its mission as addressing “issues of safety and health, amenity and sustainability”.
Its job is to set minimum standards for the design, construction and performance of buildings to “withstand extreme climate related natural hazard events”. It is then up to each state and territory to adopt the recommended standards.
After natural disasters, the ABCB examines the nature of building damage to decide whether the regulations provide enough protection. During Cyclone Tracy in 1974, 70% of Darwin’s houses suffered severe damage (90% in some areas), causing 65 deaths and damage worth hundreds of millions of dollars. It was obvious that existing building standards were not protecting the community.
As a result, the regulations were changed in the 1980s to improve the construction processes that attach the roof to the rest of the house, making homes more resistant to severe wind damage.
Analysis after cyclones Vance (1999), Larry (2006) and Yasi (2011) showed that the updated regulations have resulted in much less building damage and consequent loss of life. During Cyclone Yasi, for example, 12% of older homes suffered severe roof damage, but only 3% of newer homes.
Of course, this does not mean that newer homes are completely impregnable. Analysis of damage from Cyclone Yasi showed some remaining “weak points”: tiled roofs, sheds, garage doors, and doors/windows. It was found that more attention needs to be paid to the design, testing, installation, use and maintenance of products, components and fixings. Revised standards have since been developed for roof tiles, garage doors and shed design.
The right way to think about risk
Campbell Newman’s comment about older houses was partially correct – houses built to older standards were indeed more likely to suffer damage. But his statement is perhaps also misleading. Current building standards for Far North Queensland are designed to protect structural integrity in winds up to a Category 4 cyclone. If Ita had crossed the coast and maintained its Category 5 intensity, it is possible that all of Cooktown’s houses – old and new – would have been subject to severe damage.
It is crucial that the community understands what hazards and risks are being addressed by building regulations, and which ones are not.
For example, current regulations address wind loading associated with cyclones, but take no consideration of wind-driven rain (a major cause of water damage). There are also three specific hazards that are not addressed: hail, storm surges and heatwaves. The first two present risks to property; the third contributes to heat stress, which is in turn linked to health problems and deaths.
When deciding whether and how to update the regulations, the ABCB considers both costs and benefits. Regulations will only change if the ABCB and its stakeholders determine that the cost of the changes (such as higher building costs) are less than the benefits (the expected savings in reduced damage).
As a result, the regulations establish minimum standards, not best practice standards.
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The community’s role
Home owners and residents therefore need to be aware of these limitations in the building regulations, and be much more proactive in determining what level of risk is appropriate to their circumstances. A simple risk assessment identifies three things:
What hazards and risks might your house/unit/building be exposed to?
What is the likelihood and frequency of those hazards?
What are the consequences if the event happens?
Property damage is perhaps the first risk that people consider, particularly in relation to natural hazards such as cyclones, floods and bushfires. But buildings and their contents can also be damaged by heavy rain, hail, tidal surges, ground movement, and other phenomena.
There are also financial risks associated with not taking action, such as increased power prices and insurance premiums. These financial risks affect everyone in the community.
Meanwhile, people who are directly affected by property loss can also suffer resettlement costs and loss of income.
What should you do?
Listening to the authorities is important, but you should take responsibility for your own household risks too. One way to do it is to take out home insurance, but you need to be aware of what risks your insurance does and does not cover, and what are your responsibilities.
Another way to manage your risk is to take these things into consideration when you are building, buying or renting a property. Find out how a building has been designed and constructed to manage these risks. Ask the architect, designer, builder, estate agent, landlord, body corporate or local council for documentary evidence.
The insurance sector could also play a more proactive role in promoting better building design, perhaps by offering lower premiums for buildings with stronger construction.
Consideration also needs to be given to changing the way damaged buildings are evaluated and repaired after a disaster. New Zealand has acknowledged that the earthquake recovery process provides an opportunity for creating a more resilient city, not just restoring what was lost.
What is needed is a more collaborative approach to withstanding risks to our buildings, our property, and even our health. The ABCB seems to be moving in this direction, and it should not be expected to go it alone.
We all have a role to play in creating robust and resilient neighbourhoods that stand up to natural hazards.
Wendy Miller is senior research fellow at Queensland University of Technology.
Wendy Miller receives / has received funding from the Australian Research Council and the National Climate Change Adaptation Fund. She is being sponsored by ICPS Australia to present her research findings at the Australian and New Zealand Disaster and Emergency Management Conference on the Gold Coast in May.
This article was originally published on The Conversation.
