Years ago, I was planning a backyard room addition for a client. The addition was planned for the space occupied by an existing deck, and it seemed like a waste to demolish a perfectly good deck and tear up the yard excavating and pouring concrete. The customer owned a 2,000-sq. ft. condo in Florida that was built 10 feet off the ground on pressuretreated posts set in concrete. He thought he should be able to build a room addition in Illinois the same way, only two feet off the ground. So I asked my local code official if we could build the room addition right on top of the existing deck. It took him
