Structural Engineering Conservatory Framework

I have a pre-lim designed sketch of a conservatory style room using I-Beam framing, with aluminum slider doors inserted into the frame. A simple Steel framed roof with 2-3 degree slope and 5 rib zinc (or equiv). I need specific drawings for council submission. The drawings produced will need to be signed off by a structural engineer in New Zealand, however, due to the Christchurch Earthquake, the chances of small jobs like this will get pushed back 6 months which I do not want to wait. I want to over-emphasise the steel and therefore should have no problem with load bearing but I do need the calculations and how they should fit together. I am open to interpretation and ideas as nothing is set in stone. The room is quite simple. Its a square box. On site already there is a "hideous" 1970's style, good for nothing, single glazed conservatory which I hate with a passion, This conservatory is sitting on a concrete pad (existing structure about 3 meters x 3 meters). One side of the conservatory pushes hard against a garage and the other side to the house, with an opening to a living space. I am wanting to increase the size of the "pre-existing" concrete pad by a few meters either side by drilling rods into the "pre-existing concrete slab and concrete blocking around and filling. There is a natural slope on site, however at lowest point to solid ground its 600 mm. I will need to show weather tightness of the structure which I just assume its as easy as taking cladding off the house, adding a rubber membrane between the steel and "wooden framing of the house" and recladding, however you may have some ideas around this. I am also not opposed to a completely "flat" roof using rubber, but I do not want it looking silly or terrible so again open to thoughts around this. I am sure you will have 50 more questions, please just ask