Foundations/slab advice please

[Temp]

The method your builder suggests is pretty common. 

[IanR]

3 minutes ago, chrisb said:

 

I don't disagree @Onoff, and I may get what I asked for. I'm more concerned in the first instance on the hardcore thickness as there is significant cost /work involved.

 

Unless you've had a ground survey completed and know your soil bearing capacity I'd stick with "standard" hardcore thickness which is as per your builders suggestion. Loads are assumed to pass through the hardcore at a 45 degree angle, so for 150mm thickness of hardcore the loads is spread across an extra 300mm width of soil. Unless you know your soil can bear the extra load then I'd leave it at 150mm thick.

[chrisb]

Great, thanks for the advice. I'll stick to 150mm.

[Jeremy Harris]

Both our house slab and garage slab are on 150mm of blinded sub-base - as above it does seem to be standard for a soil with a reasonably good bearing load capacity.

[chrisb]

The next question is regarding intermediate footings. Since going to a ground-bearing slab, is there any need for the intermediate footing highlighted in yellow?

I suspect that the light blue one will be required to take the load of the first floor walls which are directly above.

Not sure about the pink one though, there is nothing above it.

 

Is a function of the intermediate footings to provide a joint in the slab to avoid cracking?