He shouldn’t be giving you options. He should be building it compliant to the building code, compliant with your plans and permits, compliant with the price of the job he quoted. Find out from your local building inspector what can be done. Make sure you get building inspector sign offs slips from the inspections.
That said, he should not build it bearing on top of an slab of unknown capacity. You dont even know how thick the the slab is.
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