A false ceiling, sometimes called a drop or suspended ceiling, is a secondary ceiling that hangs below the main ceiling with an open area between called the plenum space. The basic structure consists of a metal or plastic grid framework and removable ceiling panels. It is a popular choice for finishing basements and utility spaces, and in commercial building such as schools or offices, as it is quick, easy, and relatively inexpensive to install.
History
The drop ceiling was invented by Dan Brown of Westlake, Ohio, in 1958 to hide unfinished undersides of overhead floors.
Structure
The basic set-up is a grid pattern framework of metal brackets suspended from wires anchored to the ceiling or floor joists, drilled through a pre-existing ceiling if necessary. The framework is made of T-shaped main beams (mains), cross-tees (tees), and L-shaped wall angles. This supports the ceiling panels.
Ceiling Panels
The panels are available in 2x2 foot squares or 2x4 foot rectangles and come in a variety of styles, including insulated panels, HVAC air grilles, acoustical panels (for sound absorption), and light diffuser screens, for fluorescent lighting. The tiles can be made of wood, plastic, metal or mineral fibers.
Plenum Space
This space is necessary for housing HVAC air returns, piping, and wiring. It can also be filled with thermal insulation and/or Sound Attenuation Batts (insulation used to muffle noise).
Advantages
Ceiling tiles made of mineral fibers or fire-rated wood can help in meeting fire safety code.
The ceiling panels are easily removed, which allows quick and inexpensive access to the wiring, plumbing and duct-work housed in the plenum space for alteration, repairs or maintenance.
The ceiling panels can be switched out for different styles and/or the entire grid can be moved to change the space as desired.
Disadvantages
Reduced headroom is the biggest concern as a certain amount of clearance (generally 4 to 8 inches) is required between the lowest obstruction (wiring, piping, etc.) and the level of the grid. False ceiling also shows age quickly as ceiling tiles discolor and can begin to sag if exposed to smoke or moisture.
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