A dropped ceiling is a secondary ceiling, hung below the main (structural) ceiling. They may also be referred to as a drop ceiling, false ceiling, or suspended ceiling, and are a staple of modern construction and architecture. The area above the dropped ceiling is called the plenum place, as it is sometimes used for HVAC air return. The plenum space is also very commonly used to conceal piping, wiring, and/or ductwork.
A typical dropped ceiling consists of a grid-work of metal channels in the shape of an upside-down "T", suspended on wires from the overhead structure. These channels snap together in a regularly spaced pattern – typically a 2×2 or 2×4 foot grid in the US, or 600×600 mm grid in Europe (this is the modular size of the grid, the tiles are actually 595mm x 595mm or 595mm x 1195mm). Each cell is filled with lightweight "tiles"  or "panels" which simply drop into the grid. Tiles can be selected with a variety of materials, including wood, metal, plastic, or mineral fibres, and can come in almost any color. Light fixtures, HVAC air grilles, and other fixtures are available which can fit the same space as a tile for easy installation. Most tile material is easily cut to allow fixtures in other shapes, such as incandescent lights, speakers, and fire sprinkler heads.
The suspended ceiling was originally developed to conceal the underside of the floor above and to offer acoustic balance and control in a room. The acoustic performance of suspended ceilings has improved dramatically over the years, with enhanced sound absorption and attenuation. This is sometimes achieved by adding insulation known as Sound Attenuation Batts (SABs), more commonly referred to as "sound batts", above the panels to help deaden sounds and keep adjacent rooms quieter.
An MF ceiling comprises a lightweight galvanized metal grid which is be suspended from the structural concrete slab, steel frames or timber joists. The grid is fully concealed and finished with plasterboard and a skimmed plaster or tape jointed finish to produce a completely finished monolithic ceiling.
The primary grid is attached to the soffit with a secondary grid installed at right angles to this. This grid is suspended to the required depth of void with the use of various components. These can include acoustic hangers which will provide resilient suspension.
Standard components are available which provide simple solutions for forming ventilation ducts and for concealing other services. Bulkheads, changes to ceiling levels and access panels can easily be accommodated. MF Suspended Ceiling systems are also used externally in semi exposed areas such as undercrofts or underpasses with the correct choice of board. This hides otherwise unsightly services and can improve the fire performance.
MF ceiling construction properly specified and installed improves and fulfills fire, thermal and acoustic requirements in order to comply with building regulations and byelaws.