Decks, Patios, Porches and Docks - load ratings

My husband is designing a 28' x 70' deck, most of which will be over a ravine. Eventually a house/cabin will be built on the deck. How do we figure the load rating? We want to use steel to eliminate dozens of wood posts below and dozens of concrete columns...
The deck will start on 3 "I" beams (horizontal) perpendicular to ravine on footers, 14' apart, on concrete columns 20' apart, 2x12s bolted on plates on the columns then 2x10 decking. The legs in the ravine will be, 9 -"H" Beams on concrete columns. He is not an engineer, but a darned good builder! Thanks!

I'm sure that your husband is a great builder but you need an architect for that design. There are too many variables to avoid it.

Oh, there's no doubt that your husband is a darned good builder. But even the BEST builders (and ESPECIALLY the best builders!!) call in an engineer before they tackle something like this.

Before you attempt to design the deck structure which will support a later house, you need to design the house so that you (or an engineer) can accurately determine the magnitude and location of all loads that need to be supported by the deck.

is there water or a stream in the ravine? Will there be potential for scour of the foundation elements. Do you know the underlying soil conditions where the foundation will bear ?
You need and engineer!

JS