floating deck

I was asked a question today and for the life of me i cant find an answer on the city sites, so now im really curious about it. a friend put up a floating deck in their back yard. it touches all 3 lot lines at the rear of the site. its pressure treated wood framed w composite decking on top. being that its only a foot high or so was he required to get a permit to build this? i know there is a 3′ rule for combustible material, if you did that 3′ with all composite would that be legal? can anyone point me to the specific code on this? everything i see seems to reference decks that are attached to the building