Abstract: Prefabricated functional elements that can be made to suit all cavity-type false floors, intended to allow the running of cables and any other ducting for fluids without having to cut whole floor panels. The cavity floor panels are made up of removable and demountable functional elements positioned inside or outside a frame itself having the dimensions of a multiple or a sub-multiple of the neighboring false-flooring panels and supported by crossmembers whose spacing is variable. The functional elements inside or outside the frame can be removed individually, all at once, or in any combination, and are interchangeable.