Do I need a steel goal post arrangement?
Generally if the masonry in a structure complies with the requirements of Approved Document A you won't need steel posts, as there will be sufficient masonry to ensure that the building remains stable.
It is difficult to summarise the requirements of Approved Document A, but as brief summary if you have walls on four sides the plan area should not exceed 70m2 or if you have walls on three sides the area should not exceed 36m2 (see Diagram 5), provided you meet the requirements of Approved Document A, the structure won't need additional steel posts. Door and window openings should not exceed the dimensions as specified in Diagram 14.
If the proposed building does not comply with requirements of Approved Document A, we would recommend that you contact a suitably experienced Structural Engineer to carry out an assessment of the structure.