A raised 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 centersand 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.
In the U.S., underfloor air distribution is becoming a more common way to cool a building by using the void below the raised floor as a plenum chamber to distribute conditioned air, which has been done in Europe since the 1970s. In data centers, isolated air-conditioning zones are often associated with raised floors. Perforated tiles are traditionally placed beneath computer systems to direct conditioned air directly to them. In turn, the computing equipment is often designed to draw cooling air from below and exhaust into the room. An air conditioning unit then draws air from the room, cools it, and forces it beneath the raised floor, completing the cycle.