A suspended ceiling is a type of finish system that is hung below the ceiling structure within a room or building. It may be suspended from a roof or ceiling deck, which consists of structural framing joists that support loads above and below the deck. The majority of suspended ceiling systems are made up of steel grid and acoustical tiles, though other materials can also be used. Metal hanger wires are used to suspend these systems anywhere from three inches to more than a foot (7.6 cm to 30.5 cm) below the deck.
These ceilings can be installed over existing drywall, exposed wood framing, steel joists, or even tile ceiling finishes. In a typical suspended ceiling system, the tile is supported by thin metal frames that run in a grid pattern across the room. Wall molding is attached to the wall around the entire perimeter of the room. The remainder of the grid is suspended by hanger wires, though the ends of each grid section rest on the wall molding for extra support.
The grid may be arranged in a 2' by 4'(122 cm by 61 cm) or 2' by 2'(61 cm by 61 cm) pattern based on the standard acoustical tile sizes. Recessed fluorescent light fixtures are often used with these ceilings, and are designed to fit within the regular grid patterns. Heating and air conditioning grills may be sold in standard tile sizes so they can also be fit into a suspended ceiling grid.
A suspended ceiling offers many advantages over other types of ceiling structures. Because it is suspended below the deck, the interstitial space can serve as an air plenum for ventilation. This space can also be used to hide pipes, ducts and electrical wiring. Because the tiles are easily removable, it is still possible to access mechanical and electrical equipment above the ceiling for maintenance and service. Suspended grid systems are also relatively affordable and can be installed quickly and easily.
There are also a number of potential drawbacks to consider when choosing a suspended ceiling. Acoustical tiles tend to yellow over time, and can make a room look dated. They need to be replaced regularly, and are susceptible to stains and damage due to moisture or impact. Finally, because they are suspended below the ceiling deck, they reduce the overall ceiling height within the room. This is often considered unattractive, especially in rooms that already have a relatively low ceiling.