If this deck is a second story which means it is more than 10' out of the ground then it would be VERY prudent to have it attached to the house. I'd be surprised if your local building inspector would approve the plans for a "free standing" deck that has a height over 10'.
Most times they require them to be attached to the house as another form of bracing and structural strength for the deck.
One very real problem you will have with a deck 2' or 10' tall not attached to the dwelling is the separation that will inevitably occur.
The only time I've seen codes that don't allow decks to be attached to the dwelling is if the dwelling is a mobile home.
My advice would be to make sure it's attached to the house.
