I want to design a penthouse on top of an existing six-storey office block in the CBD but there are weight and fire requirements for the site. Is steel suitable?

Steel is definitely the best choice for framing for many reasons, not the least of which is the ease with which frames can be hoisted up without the use of cranes. If site access is severely restricted frames can be assembled on the roof. Working with steel is also not so weather dependent as it is with other materials, and CFS also means lighter foundations. There are some excellent examples of this type of construction in the Auckland Central Business District.