Stewart.. What are the dimensions of your posts and beams,(rebar plan) ,,,,size and quantity of re bar and ties...Also the size of re bar and quantity of 16mm matting.
If your plan is fully permitted then everything will be fine...If you want to go higher then you should have allowed for that in original plan.. Your municipal engineer can advise you..
Much depends on if your 1st floor slab is reinforced concrete etc etc.
All our rebar tires were tie wire.. Not sure why you need welder??