Dropped ceiling

A dropped ceiling is a secondary ceiling, hung below the main ceiling. It may also be referred to as a drop ceiling, T-bar ceiling, false ceiling, suspended ceiling, grid ceiling, drop in ceiling, drop out ceiling, or ceiling tiles and is a staple of modern construction and architecture in both residential and commercial applications.

History

Dropped ceilings and ceiling tiles were used in Japan for aesthetic reasons and for their nice taste as early as the Muromachi Period. These could be made with simple planks, or coffered. Blackfriars Theatre in London, England, built in 1596, had dropped ceilings to aid acoustics.
U. S. Patent No. 1,470,728 for modern dropped ceilings was applied for by E. E. Hall on May 28, 1919, and granted on October 16, 1923. Initially modern dropped ceilings were built using interlocking tiles and the only way to provide access for repair or inspection of the area above the tiles was by starting at the edge of the ceiling, or at a designated "key tile", and then removing contiguous tiles one at a time until the desired place of access was reached. Once the repair or inspection was completed, the tiles had to be reinstalled. This process could be time-consuming and expensive. On September 8, 1958, Donald A. Brown of Westlake, Ohio, filed for a patent for Accessible Suspended Ceiling Construction. This invention provided suspended ceiling construction in which access may readily be obtained at any desired location. Patent Number US 2,984,946 A was granted on May 23, 1961. Brown has sometimes been credited as being the inventor of the dropped ceiling even though other patents preceded his, as shown in the table below.

Date filed	Patent no.	Applicant	Title	Comments
May 28, 1919	1,470,728	Hall	Suspended Ceiling
September 3, 1931	1,931,574	Danielson	Suspended Ceiling Hanger
October 24, 1950	2,710,679	Bibb, Remmen, Bibb	Suspended Ceiling Construction	First fully developed grid system concept
December 13, 1955	2,816,623	Wong	Modular Ceiling	First integration of tiles and grid. Wong founded Cepco Manufacturing, a company later absorbed into Ceilume, a division of Empire West, Inc.
May 11, 1956	2,896,752	Wilde	Suspended Ceiling Grid Construction
July 31, 1956	2,894,291	Sorenson	Suspended Ceiling System
October 25, 1956	2,895,180	Byssing	Suspended Ceiling
February 7, 1958	2,963,251	Fuss	Supporting Electric Lighting Fixture from Suspended Ceiling Framework
September 8, 1958	2,984,946	Brown	Accessible Suspended Ceiling

Design objectives

Effective building design requires balancing multiple objectives: aesthetics, acoustics, environmental factors, and integration with the building's infrastructure—not to mention cost of construction as well as long-term operation costs.

Aesthetics

Modern dropped ceilings were initially created to hide the building infrastructure, including piping, wiring, and/or ductwork, by creating a plenum space above the dropped ceiling, while allowing access for repairs and inspections. Drop ceilings may also be used to hide problems, such as structural damage. Further, drop out ceilings can also conceal the sprinkler systems while still providing full fire suppression functionality.
For many years, dropped ceilings were made of basic white tiles, but modern innovations now offer a plethora of options in sizes, colors, materials, visual effects and shapes, patterns, and textures as well as support systems and ways to access the plenum. Custom runs of specialty ceiling tiles can be done at relatively low cost compared with the past.

Acoustics

Acoustic balance and control was another early objective of dropped ceilings. 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, more commonly referred to as "sound batts", above the panels to help deaden sounds and keep adjacent rooms quieter.

Environmental factors

Indoor environmental quality

Indoor environmental quality includes ventilation, VOC emissions, lighting and thermal system control, thermal comfort, use of daylight for natural illumination, acoustics, and optimization of outdoor view availability.

Sustainability

Many manufacturers of modern dropped ceilings include sustainability as an objective. Sustainable features may include:

Energy efficiency, including daylight efficacy and thermal insulating qualities. This uses the ceiling plane to reflect daylight as well as electrical illumination to maximize lumen efficacy, which also improves the comfort and usability of interior spaces. A common measure of the light reflectance of a ceiling material is ASTM E 1477 for Light Reflectance. A level of about 75% is considered good, although higher levels are possible.
Reduced resources needed for construction of the tiles
Recyclable/reused/renewable materials
Integration with infrastructure

Integration with mechanical, electrical, and plumbing is important with dropped ceilings, since most of these systems are by definition above the ceiling. Most ceiling system products are now designed with this integration in mind. Decisions here can also affect aesthetics as well as access and maintenance.

Cost

Dropped ceilings are likely to cost more to install than an open plenum, but may offer significant cost savings in maintenance and energy.

Suspension grids

A typical dropped ceiling consists of a gridwork 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 of cells. Each cell is then filled with lightweight ceiling tiles or "panels" which simply drop into the grid. The primary grid types are "Standard1", Slimline, and concealed grid.
In the United States and its neighboring countries, the cell size in the suspension grids is typically either or, and the ceiling tiles, light fixtures, and fluorescent light tubes are the same size. In Europe, the cell size in the suspension grids is 600×600 mm, while the ceiling tiles and fixtures are slightly smaller at or, and the T5fluorescent and LED tubes are shorter by 37 mm to allow for easier and safer insertion and removal without breakage.

Concealed grid

An older, less common type of dropped ceiling is the concealed grid system, which uses a method of interlocking panels into one another and the grid with the use of small strips of metal called "splines". Normally, they have a "key panel" that can be removed, allowing for the other panels to be slid out of the grid one by one, until eventually removing the desired panel. This type of ceiling is more commonly found in older installations or installations where access to above the ceiling is generally considered unnecessary.
This system has some major disadvantages compared to the more common "drop panel" system, notably the difficulty in removing and reattaching panels from the grid, which, in some cases, can cause irreparable damage to the panels removed. Finding replacement panels for this type of dropped ceiling is becoming increasingly more difficult as the demand for them and the production of parts slow. Small clips are available that allow tiles to be inserted into gaps in the ceiling where a tile is missing and work by being placed on the edge of a concealed tile and then being slid along as the tile is placed to lock it in place.

Stretch ceiling

With similar advantages to a dropped ceiling, a stretch ceiling is often used to conceal pipework, wires or the existing ceiling. There is also usually a broad choice of colour or texture, and the membrane can be manipulated into a variety of shapes.
A stretch ceiling is a suspended ceiling system and it is made of three main components:

Perimeter track – Aluminium or plastic PVC
Membrane – Typically a PVC or nylon material, lightweight sheets are made to size/shape from roll material. Can be printed or painted to achieve the desired effect.
Harpoon or catch – This is ultrasonically welded to the edge of the membrane or sheet in the factory, the edging slots into the perimeter track to keep the ceiling in place.

When a stretch ceiling is being installed, semi-concealed plastic/aluminum track, the preferred choice for most architects and designers, is cut to size and fixed to the perimeter of the ceiling area. The membrane is stretched and the harpoon or catch edge is clipped into the track. Stretching is aided by heating up the membrane or sheet prior to fitting.

Drop out ceilings

Approved drop out ceilings allow the installation of a dropped ceiling beneath existing fire sprinklers because the tiles, sometimes called melt-out ceiling tiles, are heat-sensitive and are designed to fall from the dropped ceiling suspension grid during a fire, allowing the sprinklers to spray their water.
Drop out ceiling tiles can add to the aesthetic appeal of a ceiling since the fire sprinklers are hidden by the tiles. Commonly made from vinyl or expanded polystyrene, drop out ceiling tiles are available in multiple sizes and finishes from a variety of manufacturers.
Installation is subject to the local Authority Having Jurisdiction and, in the United States, must meet the standards listed in the section below at a minimum.