What size steel I-beam to support a concrete floor weighing 6.3 tonnes?
You will have to get this one properly engineered by a structural engineer, and then submitted for council approval. If you could tell me all the dimensions of the beam or even better give me the moment of inertia (listed as Iy under engineering properties) I could give you an indication as to what spacing of the support colums you could get away with. But I am not familiar with the building codes and standards for domestic buildings and withut seeing the full plans of the area could not say exactly what size the beam needs to be, and what size and spacing you need the columns, no other engineer will either without seein the full plans. You could get away with a single beam and and only two columns, but the size of these members will need to be properly determined. You may get some builders that think they know, but without getting it properly engineered and council approved, if it were to ever fall down and injure or kill someone, you would be in very deep legal poo.
