We built a house with AV Jennings in 1990 and the concreter said that we had enough steel and concrete in the slab to build a 3 storey home on. We built a single storey on that slab, I don't remember how deep the trenches were but I remember we were building on soil that had 'E' classification. Extremely reactive soil at Hackham.
Is your slab still looking a bit on the large side?
I forgot to say that I love Jacarandas. The one out front of your house looks like it is well established. I won't be planting one in our front yard as I think we will have enough purple at our place.
Our dirt is H-D. They tell us that this means highly reactive clay, with deep moisture movement. I have no idea what that means, but it translated to a lot of concrete and a lot of steel mesh !
Yes the trees are quite old, the whole suburb is full of them, spectacular in spring !
Oh and the pad still looks enormous but no different from yesterday, can't blame them, the weather was disgracefully hot today