https://www.abc.net.au/news/2018-11-29/queensland-bushfire-gracemere-residents-return-home/10564880

In this article, it is explained how a catastrophic rating is achieved. It also says “no houses are built to withstand catastrophic conditions”.

Apart from living underground, is it possible to design and build a house that will withstand a catastrophic fire?

I should think it would be possible but the “house” would be more like a massively insulated bunker.

Divine Angel said:

https://www.abc.net.au/news/2018-11-29/queensland-bushfire-gracemere-residents-return-home/10564880

In this article, it is explained how a catastrophic rating is achieved. It also says “no houses are built to withstand catastrophic conditions”.

Apart from living underground, is it possible to design and build a house that will withstand a catastrophic fire?

That’s a darn good question.

My opinion on this has swung back and forth several times over the past 20 years or so.

In a nutshell, it comes down to how catastrophic is catastrophic.

But even defining catastrophic in this case isn’t easy. Different factors are: the fire temperature, the intensity of radiant heat, the duration, the wind speed, ember production, and the amount of oxygen, carbon dioxide and carbon monoxide in the air.

The homes in the Canberra fire were destroyed because of the wind speed. The wind speed was tornado strength so ripped the roofs off houses and toppled trees into houses, after which embers from the fire took an easy foothold.

In Marysville, I saw titanium that has melted off a truck. I also saw something that had burnt despite being underground and covered by a metre of earth.

On the other hand, some places in Marysville were completed unscathed and a video of the fire there taken from the park in the centre of town didn’t look too bad at all.

Some people have taken to installing a sprinkler system on the roof. On the other hand, a kangaroo that had taken refuge under a sprinkler system in the lawn died from smoke inhalation.

Glass subject to radiant heat turns black, and then cracks. Glass is not safe in a catastrophic fire.

I have a lot more to say on the subject. But need to get my thoughts in order first.

View from space of the Queensland bushfires taken by the Himawari 8 Japanese weather satellite.

From:
https://www.abc.net.au/news/2018-11-29/queensland-bushfire-gracemere-residents-return-home/10564880

The affectionately named “straw house” was blasted with a range of real life bushfire conditions, from a radiation build up phase to full flame immersion and then a radiation decay phase.

So how did it fair? The external temperature reached a scorching 1000°C while inside the house was a cool 35°C. There was minimal damage to the straw house’s cladding and while the steel frame heated up  to 100–110°C it remained structurally sound and intact.

https://blog.csiro.au/straw-house-1-fire-0/

Somewhere central coast Qld.. “Beautiful One Day…

Some back-of-envelope thinking.

I have read some contemporary descriptions of the Black Friday fires in Victoria in January 1939. Something like 2 million hectares burnt.

https://www.ffm.vic.gov.au/history-and-incidents/black-friday-1939

Mr buffy had an uncle who was a sawmiller in Gippsland and survived to walk out. I don’t know how. In the description I recall reading there were fire bunkers…caves dug into the soil. People retreated into them, there was hessian curtains across the door and they had water that they kept flinging at the hessian to stop it catching fire. Must have been quite horrible. When I was a child, I’m sure there were fire bunkers through the Dandenongs.

Divine Angel said:

https://www.abc.net.au/news/2018-11-29/queensland-bushfire-gracemere-residents-return-home/10564880

In this article, it is explained how a catastrophic rating is achieved. It also says “no houses are built to withstand catastrophic conditions”.

Apart from living underground, is it possible to design and build a house that will withstand a catastrophic fire?

I’m still not sure. More than anything it comes down to radiant heat.

If the heat is enough to melt brick, then a lot of even fireproof houses would go. But concrete would still survive.

Aluminium and glass are bad, both start to give way at about 660 degrees. Protection of glass against flying debris by laminating it only serves to make its thermal performance worse. Double glazing only adds a few more minutes. They would have to be protected by steel shutters.

Water is a help, so long as it lasts, but would need a power supply that cannot be starved of oxygen. Far too many people have died in fires when the water that they are hiding in boils. It’s better to hide behind a water tank than in it.

I think that an ember-proof house with a buffer zone free of trees and all other burnable materials around it, made of concrete (eg. tilt slab) with steel shutters over the windows and doors, would be proof against any conceivable catastrophic bush fire, so long as the air lasts.

Bunkes would have to be deeper than the average Hungi trench.

catastrophic

got a big feel that word. Probably the same word you’d use to describe being sucked into a black hole

transition said:

catastrophic

got a big feel that word. Probably the same word you’d use to describe being sucked into a black hole

Or attacked by stroppy cats

Cymek said:

transition said:

catastrophic

got a big feel that word. Probably the same word you’d use to describe being sucked into a black hole

Or attacked by stroppy cats

Think I’d prefer the black hole.

Cymek said:

transition said:

catastrophic

got a big feel that word. Probably the same word you’d use to describe being sucked into a black hole

Or attacked by stroppy cats

Or musical cats.

The article linked in the OP said that Deepwater had a rating of 135 and Emerald had a rating of 105. Anything over 100 is “catastrophic”.
http://www.bom.gov.au/weather-services/bushfire/index.shtml

This is a simple article explaining how those numbers are obtained.
https://www.csiro.au/en/Research/Environment/Extreme-Events/Bushfire/Fire-danger-meters/Mk5-forest-fire-danger-meter

However, when fire danger is rated catastrophic, no home is built to withstand those fires.
https://www.cfs.sa.gov.au/site/bans_and_ratings/more_about_fire_danger_ratings.jsp

The system was developed by Arthur McArthur and Catastrophic was added after the Victorian bushfires of 2009.
https://www.abc.net.au/news/2017-12-13/bushfire-danger-rating-system-trialled-summer/9203446

Son got home after most of a day’s work.. stuffed max.. only to receive a text alert, Watch and Act, about “a bushfire in the Stanwell and Kabra areas and conditions are getting worse.”

This is just to the west of Gracemere with the fire heading north.

I think he’s gone to bed.

Ian said:

Son got home after most of a day’s work.. stuffed max.. only to receive a text alert, Watch and Act, about “a bushfire in the Stanwell and Kabra areas and conditions are getting worse.”

This is just to the west of Gracemere with the fire heading north.

I think he’s gone to bed.

Well he should get out again.

Ian said:

Son got home after most of a day’s work.. stuffed max.. only to receive a text alert, Watch and Act, about “a bushfire in the Stanwell and Kabra areas and conditions are getting worse.”

This is just to the west of Gracemere with the fire heading north.

I think he’s gone to bed.

Bugger.

Divine Angel said:

The article linked in the OP said that Deepwater had a rating of 135 and Emerald had a rating of 105. Anything over 100 is “catastrophic”.
http://www.bom.gov.au/weather-services/bushfire/index.shtml

This is a simple article explaining how those numbers are obtained.
https://www.csiro.au/en/Research/Environment/Extreme-Events/Bushfire/Fire-danger-meters/Mk5-forest-fire-danger-meter

However, when fire danger is rated catastrophic, no home is built to withstand those fires.
https://www.cfs.sa.gov.au/site/bans_and_ratings/more_about_fire_danger_ratings.jsp

The system was developed by Arthur McArthur and Catastrophic was added after the Victorian bushfires of 2009.
https://www.abc.net.au/news/2017-12-13/bushfire-danger-rating-system-trialled-summer/9203446

There’s another way to tell if a bush fire is catastrophic. If the greens own the council then it’s catastrophic. It was the policies of the greens on the local council that doomed Marysville in 2009.

Will read your links. I used to work with Justin Leonard, who is/was CSIRO’s bushfire expert.

> https://www.csiro.au/en/Research/Environment/Extreme-Events/Bushfire/Fire-danger-meters/Mk5-forest-fire-danger-meter

> designed for general forecasting purposes and is based on the expected behaviour of fires burning for an extended period in high eucalypt forest carrying a fine fuel load of 12.5 tonnes/hectare.

You see. That’s where it fails. You can’t assume a fuel load of 12.5 tonnes per hectare. The actual fuel load depends on the amount of back burning done over at least the previous 15 years. Also, the danger depends on the size of the buffer zone between the forest and the houses.

mollwollfumble said:

> https://www.csiro.au/en/Research/Environment/Extreme-Events/Bushfire/Fire-danger-meters/Mk5-forest-fire-danger-meter

> designed for general forecasting purposes and is based on the expected behaviour of fires burning for an extended period in high eucalypt forest carrying a fine fuel load of 12.5 tonnes/hectare.

You see. That’s where it fails. You can’t assume a fuel load of 12.5 tonnes per hectare. The actual fuel load depends on the amount of back burning done over at least the previous 15 years. Also, the danger depends on the size of the buffer zone between the forest and the houses.

in Canberra’s worst bush fire, the fire front came down the Brindabellas ranges towards the suburb at the bottom with no buffer zone.

instead the buffer zone became 4 houses (2 blocks) deep before it stopped.

Around 470 homes lost.

mollwollfumble said:

Divine Angel said:

The article linked in the OP said that Deepwater had a rating of 135 and Emerald had a rating of 105. Anything over 100 is “catastrophic”.
http://www.bom.gov.au/weather-services/bushfire/index.shtml

This is a simple article explaining how those numbers are obtained.
https://www.csiro.au/en/Research/Environment/Extreme-Events/Bushfire/Fire-danger-meters/Mk5-forest-fire-danger-meter

However, when fire danger is rated catastrophic, no home is built to withstand those fires.
https://www.cfs.sa.gov.au/site/bans_and_ratings/more_about_fire_danger_ratings.jsp

The system was developed by Arthur McArthur and Catastrophic was added after the Victorian bushfires of 2009.
https://www.abc.net.au/news/2017-12-13/bushfire-danger-rating-system-trialled-summer/9203446

There’s another way to tell if a bush fire is catastrophic. If the greens own the council then it’s catastrophic. It was the policies of the greens on the local council that doomed Marysville in 2009.

Will read your links. I used to work with Justin Leonard, who is/was CSIRO’s bushfire expert.

It would seem Justin Leonard was concerned with the reaction of bushfires on buildings rather than the bush itself. Not sure what the Greens have to do with fire prevention and would imagine it would be very varied and largely dependent on the knowledge of the individual. Don’t think you achieve much by condemning the entire organisation or movement, especially as people concerned with the environment are labelled as being green, when their ideals can be very realistic and scientifically based.

>>Justin Leonard has dedicated the last 20 of his 24 year research career to the understanding of how bushfire risk to life and infrastructure can be managed. His work has built on the learning of an already established research area within CSIRO in which he was initially mentored and then inherited. The research area combines learnings from bushfire exposure experiments with post bushfire survey investigations and computer modelling of bushfire interactions with buildings.

Recent activities include the development and delivery of accreditations course on bushfire risk assessment with Melbourne University, providing technical support for the Victorian Community Bushfire Community Refuge Program, developing the bushfire planning risk maps for Queensland, development of a comprehensive life/house loss database for Australia, developing innovative ways to perform post bushfire surveys and assisting various individuals and industry groups develop novel building design solutions and related standards.<<