Hire builder or owner builder for structural slab?

thanks for the reply. I'm in QLD.

Hi Ardo thanks for the reply. I should have added more details in my original post. The high set house is existing and has been raised to legal height by the previous owners. There's no concrete slab underneath just gravel. Our plan is to have a plumber install the plumbing required for the downstairs bathroom and laundry before the slab is poured.

Hi Alex a couple of reasons why we want to pour a slab is that the backyard slopes down towards the house and when it storms underneath the house gets muddy and the water pools due to it being level. Previous owners installed strip drains but the grills keep getting clogged with gravel etc. The other is once the slab is poured the intenion is to build in eventually due to it being legal height underneath. The other reason is when the slab is poured and before we build in is we are hoping that we would use the space a bit more as it connects with the backyard very well which is handy with the kids.

Got a recent quote to pave and the paving guy said you might as well get it slabbed due to the cost being similar, which was surprising.