Bedroom addition on stilts

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We want to enlarge our master bedroom (13' side wall x 11' back wall) and add a bath w/ shower. We have a 30 yr old, 24' x 44' bi-level house, cinder block foundation. We would like to build out the back wall 10 ft and across the back of the house 22 ft. the opening on the house itself will be 11' The houses foundation 3 ft underground in the back and the floor of the br is about 8 ft off the ground. I would rather not have to put in a whole foundation for tax and cost reasons. i see some neighbors put there additions on stilts (iron?). Is this a good way to go ? We live in lower NY State. Thanks for your help.

PS: Also instead of a roof I want to put a sundeck on the top of the addition, accessible from outside deck. That might cut down on the weight, don't you think?