DisastersHow building codes save homes from cyclones, and how they don’t
During Queensland’s preparations for Severe Tropical Cyclone Ita, 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. 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?
During Queensland’s preparations for Severe Tropical Cyclone Ita, 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 percent of Darwin’s houses suffered severe damage (90 percent 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 percent of older homes suffered severe roof damage, but only 3 percent of newer homes.
