There was a tornado in South Auckland recently and it did the usual amount of damage that these things do.
Reporters wrote about the tornado as if it was a rare event linked to global warming, but these unfortunate localised storms have been hitting parts of our country for years and we don’t seem to be learning the lessons from them.
There is not much that one can do to avoid a tornado if it does strike, and the likelihood of one’s own home being hit is in the order of wining Lotto; but there are obvious construction choices that can reduce the impact, both physically and economically.
Some forms of construction are more resistant, and others much cheaper to repair. As damage is usually primarily to the roof of a dwelling, that is where the best opportunity to make a good material choice can be made.
There was a very similar tornado that struck near where my father’s house was way back when I was learning to be an engineer and it seems that the lessons offered then have not been learned.
Three main types of roof were hit, corrugated iron, concrete roof tiles and a flat roof with a torch-on membrane.
The corrugated roof was lifted up and folded back down over the ridge to reveal a gaping hole into the house which was below the road. This looked bad but within a day it had been refolded and refastened back in place.
The concrete tiled house didn’t appear too bad as about 70% of the tiles had stayed in place, however the 30% that hadn’t, had fallen into the house smashing ceilings, walls, furniture and fittings. Repairs took weeks and cost heaps.
The flat roof was over a retirement complex and a large chunk lifted up, including ceilings and wall parts, and was dropped outside the building. Sadly, two elderly ladies died in the rubble. This repair was also major, expensive and slow.
The recent tornado showed exactly the same thing happening. Corrugated iron lifted off but was easily and quickly repaired and heavy concrete roof tiles spread around with a large workforce involved in replacing the roof and whatever the unknown damage below was.
Why do we persevere with roof tiles? They performed very poorly in the Christchurch earthquake too.
I just hope things have worked out for those involved in the recent tornado and hope that they were insured. The recent storm showed that far too many people were uninsured and they can’t rely on the rest of us if they have decided to take that risk themselves. Lessons! (Wayne Brown)
www.facebook.com/WayneBrown4Auckland
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PUBLISHED 5 MAY 2023