Roofs fail to defend against frequent hailstorms, study reveals

Oct 27, 2008

(PhysOrg.com) -- A new study of hailstorms in Sydney has found many of the city's roofs are unable to resist the large hailstones expected to hit every 10 years.

Professor Alan Jeary, from the UWS School of Engineering, has used innovative techniques to determine the interval between hailstorms and the likely size of the hailstones that fall.

In the past 20 years, Sydney has been hit by six significant hailstorms which have caused over $5 billion* damage. The December 2007 storm in Blacktown alone is expected to cost in excess of $400 million.

Despite the economic, physical and emotional toll the storms have on communities, Professor Jeary says Australian Building Codes do not currently acknowledge the potential danger of hail.

"The current wind codes in Australia require buildings to withstand a one in 1000 year wind storm, yet preliminary data analysis suggests the devastating hailstorm in Blacktown last December could happen as often as every 10 to 15 years," says Professor Jeary.

Using an innovative technique that was originally used to analyse windstorms in Denmark, Professor Jeary has studied Sydney hailstorms.

The preliminary findings show:

* Hail 30 to 40mm in diameter, which breaks glass and plastic, recurs every 5 years
* Hail 40 to 50mm, which cracks old slate and other tiles, recurs every 10 years
* Hail 50 to 60mm, which breaks old slate and other old tiles and cracks new tiles, recurs every 15 years
* Hail 60 to 75mm, which breaks new concrete and terracotta tiles, recurs every 20 years
* Hail 75 to 85mm, which breaks all new tile and slate roofs and dents corrugated metal roofs, recurs every 50 years.

According to Professor Jeary, a key element of any building code relating to natural events is establishing how frequently they occur and how significant any single event is likely to be.

"Using standard statistical measures, there hasn't been sufficient historical data on hail size to establish the risk of hail damage - so the threat has been being largely ignored by regulators, builders and manufacturers," he says.

However, Professor Jeary believes the preliminary figures from the new study demonstrate there is a pressing need to closely examine the standards for roofing and establish new guidelines so roofs can resist hail damage.

"It is extraordinary to contemplate replacing a roof potentially every 10 years because of hail damage," he says.

*adjusted to equivalent in 2007 dollars

Provided by University of Western Sydney

Explore further: Managing the “Internet of Things

Related Stories

Assuring solar modules will last for decades

Apr 14, 2015

The Energy Department's National Renewable Energy Laboratory (NREL) is co-leading an international push to assure the reliability of solar panels—an assurance demanded by customers, manufacturers, lenders, ...

NREL test helps make moisture barriers better

Nov 26, 2013

Moisture—in the form of humidity, water spills, or rainfall—spells early demise for cell phones, light-emitting diode (LED) displays, TVs, and solar photovoltaic (PV) panels worldwide.

Explainer: Why are tornadoes so destructive?

May 22, 2013

Tornadoes are a part of life for people living in the Great Plains of the United States. In Oklahoma, a state that averages 62 tornadoes a year, people are prepared as best as they can be and are well warned.

Recommended for you

Managing the “Internet of Things

10 hours ago

Researchers in Hong Kong have developed a software platform designed to manage and control devices for "Internet of Things" (IoT) systems. The platform can be tailored for everything from city management ...

Off-road run-ins for driverless fleets

May 28, 2015

Carlos Holguin from the University of Rome, project coordinator with the CITYMOBIL2 project, talks about how the project is demonstrating automated road passenger transport through large and small-scale off-normal traffic ex ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.