Author Topic: Sydney roofs 'can't cope' with big hail  (Read 11139 times)

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Offline Richary

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Sydney roofs 'can't cope' with big hail
« on: 28 October 2008, 12:38:33 PM »

From the Sydney Morning Herald news website...

October 27, 2008 - 6:23PM


Many of Sydney's roofs are inadequate to cope with major hailstorms, such as the devastating downpour in the city's west last summer, a study shows.

Professor Alan Jeary from the University of Western Sydney said Australian building codes did not acknowledge the terrible impact of hail, despite Sydney suffering six severe storms in the past 20 years.

The storms have cost billions of dollars in damages, including about $2 billion in a 1999 storm which pummelled parts of Sydney.

Damage of more than $400 million was recorded in the Blacktown area after a violent storm last summer, which led to 58,000 insurance claims.

"The current wind codes in Australia require buildings to withstand a one in 1,000 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," said Prof Jeary, from the university's school of engineering.

The study found hail was a recurrent problem in Sydney, with stones between 30-40mm in diameter falling every five years.

Hailstones of 40-50mm, which can crack old slate and other tiles, happen every 10 years.

Hail of 60-75mm, which can break new concrete and terracotta tiles, was recorded every 20 years, the study found.

Prof Jeary said there had not been sufficient historical data kept on hail storms to properly assess the risk of hail damage.

He said new building standards should be drawn up to ensure tiling was more resilient to hail.

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

Offline Mike

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Re: Sydney roofs 'can't cope' with big hail
« Reply #1 on: 28 October 2008, 08:42:12 PM »
When they're as big as cricket balls that's a given.  Some bean counter will jump on this and up go the premiums - just in case there's a hail storm.  A bit like paying premium tornado insurance - you pay for it just in case one drops on your house - lat/long required in the fine print to be sure due to the unknown science of exactly what time it will happen and where.
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Offline Jimmy Deguara

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Re: Sydney roofs 'can't cope' with big hail
« Reply #2 on: 29 October 2008, 01:00:39 AM »
Mike,

I would suspect this has already been done - insurance companies often paying these researchers to look into such studies as has been noted in a report like this and yes that is passed across to their beloved customers. Of course, I am not against the concept of research - I just think it would be better utilised to help save lives and property.

Back on topic, there are a few studies like these around that specifically targetted the Sydney hailstorm in 1999. In that case, they tried to determine what types of roofs were better suited and held up against even larger hailstones.

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Offline Richary

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Re: Sydney roofs 'can't cope' with big hail
« Reply #3 on: 29 October 2008, 03:12:22 AM »
There is probably a lot to be said for a colourbond or similar steel roof!

I remember from the 1999 storm, I had to go from the city up to the Paddington International Telephone Exchange the next day. From the top of the exchange looking out every tile/slate roof visible was trashed. And on the trip up every car on one side of the road had the windscreen smashed, on the other side of the road it was the rear window.

Offline Michael Bath

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Re: Sydney roofs 'can't cope' with big hail
« Reply #4 on: 29 October 2008, 04:09:21 AM »
Yes, the colourbond roofs are certainly going to offer protection from the giant hail smashing though into the ceiling and inside the house. We have it on our home.

But they still have to be replaced by insurance if hit by large hail - as the impacts crack the colourbond coating and they then rust.
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Offline Harley Pearman

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Re: Sydney roofs 'can't cope' with big hail
« Reply #5 on: 29 October 2008, 01:07:27 PM »
Further on this subject, I attended the Planning Institute Australia annual yearly conference back in April 2008 and the topic Plenary Session 1 - A Climate for Change Presentation Title - "Economic Issues relating to Climate Change" partially looked at this area.

Insurance companies such as IAG are well aware of hail impacts on house roofs and building materials used to construct homes.

Sam Mostyn (IAG) who led the Plenary indicated to the gallery with graphs and facts there has been a tendency for more extreme weather events leading to more insurance payouts. However families pay when damage is done via the premiums paid. The most costly events noted were the hailstorms. A hailstorm is an issue and Sydney was used as the Australian example due to the number that have occurred.

IAG stated that they have made large payouts from 8 hailstorms over recent times.

Sam indicated that a 7 cm hailstone will break a roof tile but not penetrate corrugated iron. The BCA (Building Code of Australia) does not address this too well and it needs to be revamped to address hailstorms.

The Blacktown hail event (Also discussed briefly at the Plenary) racked an insurance payout of around $388 million but other loses took the figure to around $460 million (uninsured loses or other loses not covered).

IAG even mentioned that insurance companies may even take the lead to have the BCA toughened to address severe thunderstorm events in cities and towns with emphasis on roofing materials for new homes. This is an area that should be watched.


Harley Pearman

Offline Jimmy Deguara

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Re: Sydney roofs 'can't cope' with big hail
« Reply #6 on: 29 October 2008, 02:43:02 PM »
Michael,

The concept of having metal roofing even if having to be replaced saves from that internal damage (and damage of valuable or sentimental items) I have hinted to in the past that I believe contributed to some major increase in insurance costs in the 1999 Sydney hailstorm.

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Offline angielily18

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Re: Sydney roofs 'can't cope' with big hail
« Reply #7 on: 25 August 2010, 09:09:37 PM »
Hail is just stones that thrown into your roof. So, it is better that you have a stronger roof like metal roofs that could withstand the wait and impact of the hail in the roof.

Offline Colin Maitland

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Re: Sydney roofs 'can't cope' with big hail
« Reply #8 on: 26 August 2010, 12:39:31 PM »
Just noticed this thread from the last post. As a builder and being in the industry for 26 years, metal roofs are the wisest choice, albeit, I have seen hail penetrate such roofs, an example of this was a hailstorm here in Brisbane that hit Anstead, a western suburb.

I would not have a tiled roof again. They become brittle with time and just smash during a good hail storm. Also, if you have ever hopped up inside your roof during a storm or during windy rain, you will notice the tiles lifting and water spraying through.

The Building Code of Australia has a formula that designers and builders have to use to optimize the flow of water off the roof as quickly and effectively as possible. It determines how many down pipes are needed, plus there is a lot of consideration into how many valleys, gables etc etc a roof will have. The more complicated the roof, which seems to be the go for aesthetics these days the more problems you will have.

Keeping the roof simple, having a pitch of at least 20 degree,using the right gauge metal, a good heavy duty sarking and using a reputable trust worthy roofer to install it is of utmost importance.

During many of the storms and heavy rains we have in QLD, I am yet to see a roof cope with the amount of water that accumulates in the short periods, that is why you will notice slots cut into your gutters approximately 1/3 from the top. This is to allow water to escape, but that still does not work in a absolute down pour.

So you can understand why hail, being a solid object will back up quickly, block your gutters and as the heavy rains follow it will flow back into your roof lining and flood your roofs if you dont have soffitts.
   

Offline angielily18

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Re: Sydney roofs 'can't cope' with big hail
« Reply #9 on: 31 August 2010, 06:35:52 PM »
Hail is very dangerous. You do need a very sturdy roof that can withstand hail. I recommend metal roofing, this is a very strong roof and can stand all types of weather. More expensive than asphalt roofing, but will prove to be more economical as this will last many years.

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« Last Edit: 31 August 2010, 09:35:24 PM by angielily18 »