Hi I live in an area that was devastated by wildfires some years ago. I have a SIPs house with hardiboard siding and a steel roof now. It is 3 stories on one side, two on the others. I want to put some balconies up for access to the tallest side of the house (I'm on a slope) but I don't want to go the standard wood route. I also don't want posts going up 3 stories, though maybe I have to. So, question 1) what would be the most cost effective material that is, at least, fire resistant, and 2) if I only want access, not a deck for recreation, could I cantilever off the side of the house? Many thanks for any suggestions.

http://www.finehomebuilding.com/how-to/articles/fire-resistant-details.aspx

Well probably anything beyond a ladder(basically supported off the ground), and certainly anything cantilevered off the wall really needs to involve your engineer. Unless it was planned into the structure's design from the beginning, it may be a problem and really expensive to reconfigure the structure for tat required support.

As for fire resistance, I really like steel and concrete Something such as a steel spiral staircase with a steel center column set in concrete and support struts to the building might be able to provide a small landing at each level for access/egress without requiring too much structural alteration to the building. It would basically be self supporting on a well set center column...

Concrete is very cheap and flame resistant. Since you're not really looking for a recreational deck, concrete is probably the best option because of the cost, even though it's not as aesthetically pleasing as other materials.