SWMBO's 1865 family farmhouse was lost in the 2020 bushfires. It was insured so the losses were all personal. However not one shed burned despite evidence of flames licking up the iron from the ground. They contained lots of flammables, tractors, the old landcruiser ute etc.

Originally I thought it was sheer luck until I discovered what I think is the reason why they survived. They all had a little wall three bricks high around the perimeter of the slab on the inside. Even the open shed with a dirt floor had the same. In my sheds, the iron runs down below the slab and is fixed to a 90x45 dyna bolted to the slab. If flames started licking up under the iron, the timber would burn. But if the timber was 300mm up the wall, it would be far less likely to catch.

BTW, the frames were all fixed to the slabs with strapping against wind damage,

mick