False Flooring:

A false flooring (also raised flooring, access floor(ing), or raised access computer floor),provides an elevated structural floor above a solid substrate (often a concrete slab) to create a hidden void for the passage of mechanical and electrical services. Raised floors are widely used in modern office buildings, and in specialized areas such as command centers, IT data centers and computer rooms, where there is a requirement to route mechanical services and cables, wiring, and electrical supply. Such flooring can be installed at varying heights from 2 inches (51 mm) to heights above 4 feet (1,200 mm) to suit services that may be accommodated beneath. Additional structural support and lighting are often provided when a floor is raised enough for a person to crawl or even walk beneath.