100mm thick reinforced slab is all that is required as when shed is erected the vertical support columns will be bolted/concreted into thier own footing first,then once shed is assembled you go in and concrete the floor last.
This is the most common method of shed building in W.A
Hope this is of some help,most country towns have someone who specialises in shed erection/builing etc rather than a house type builder.
Regards Aggy
