A dropped ceiling is a secondary ceiling, hung below the main (structural) 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.
Dropped ceilings and ceiling tiles were used in Japan for aesthetic reasons as early as the Muromachi Period (1337 to 1573). [1] These could be made with simple planks, [2] or coffered. [1] Blackfriars Theatre in London, England, built in 1596, had dropped ceilings to aid acoustics. [3]
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. [4] 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. [5] Brown has sometimes been credited as being the inventor of the dropped ceiling [6] 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 |
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. [7]
Modern dropped ceilings were initially created to hide the building infrastructure, including piping, wiring, and/or ductwork, [4] 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 (including retro designs and faux leather, wood, or metal), visual effects and shapes, patterns, and textures as well as support systems and ways to access the plenum. [8] Custom runs of specialty ceiling tiles can be done at relatively low cost compared with the past.
Acoustic balance and control was another early objective of dropped ceilings. [9] A noisy room can overstimulate occupants, while a too quiet interior may seem dull and uninviting.
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. [10]
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.
Many manufacturers of modern dropped ceilings include sustainability as an objective. Sustainable features may include:
Integration with mechanical, electrical, and plumbing (MEP) 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. [7]
Dropped ceilings may have an improved return on investment (ROI) over open ceilings [11]
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 "Standard 1" (15⁄16-inch face), Slimline (9⁄16-inch grid), and concealed grid.
In the United States and its neighboring countries, the cell size in the suspension grids is typically either 2 by 2 feet (610 mm × 610 mm) or 2 by 4 feet (610 mm × 1,220 mm), 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 (5 mm) smaller at 595×595 mm or 595×1195 mm, and the T5 fluorescent and LED tubes are shorter by 37 mm to allow for easier and safer insertion and removal without breakage.
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', thus making it difficult to remove panels to gain access above the ceiling without damaging the installation or the panels. Normally, they have a "key panel" (usually in the corner) that can be removed, allowing for the other panels to be slid out of the grid (a series of metal channels called "z bars") 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, most 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 still 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.
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. [12]
A stretch ceiling is a suspended ceiling system and it is made of three main components:
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.[ citation needed ] Stretching is aided by heating up the membrane or sheet prior to fitting.
Approved drop out (or 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 (AHJ) and, in the United States, must meet the standards listed in the section below at a minimum.
The following standards are in addition to those for ceiling tiles in general. No clips, fasteners, or impediments of any kind can be used to limit the ceiling tile's ability to drop from the suspension system without restraint in the event of a fire unless they have been used in the testing process. Painting can void an approval, and additional local requirements may exist.
In older buildings, the space above the dropped ceiling was often used as a plenum space for ventilation systems, requiring only enclosed ducts that deliver fresh air into the room below, with return air entering the ceiling space through open grilles across the ceiling. That practice is now used less frequently in new buildings.[ citation needed ]
If the dropped ceiling is used as a plenum, low-voltage cables and wiring that are not installed inside conduit must use a special low-smoke and low-toxicity wire insulation, which will tend to char and stop burning on its own. That helps to protect building occupants so that they are not poisoned with toxic chemicals sucked through the ventilation system during a fire, and it helps to prevent fires from spreading inside the hidden plenum space. The special low-smoke cable is typically referred to as plenum cable or Low Smoke Zero Halogen (LSZH or LS0H) cable. While twisted pair cable for networking and telephone service is the most common form of plenum cable, coaxial cable also needs to be plenum-rated for safety.
High-voltage electrical equipment (generally regarded as being over 50 V) is not permitted to be exposed in the plenum space above a drop ceiling but must be enclosed in conduit or raceways and be physically isolated from low-voltage wiring. High-voltage electrical devices similarly must be enclosed in a plenum space, inside a metallic container. Similarly, electrical outlets for domestic powered devices may not be inside the plenum space, but outlets can be installed on ceiling tiles inside electrical boxes, with the sockets exposed on the exterior bottom face of the drop ceiling. The purpose of these restrictions is to limit flame spread inside the unseen plenum space, in the event of high voltage equipment or wiring failure. Low-voltage cabling is permitted because current flow is typically negligible and so the risk of overheating and fire is limited.
In earthquake prone areas, such as California, diagonal wire stays are often required by building codes to prevent the ceiling grid from swaying laterally during an earthquake, which can lead to partial or total collapse of the ceiling grid on the occupants below during a severe tremor. Compression posts may also be added to keep the ceiling from bouncing vertically during an earthquake.
Lighting fixtures and other devices installed in a dropped ceiling must be firmly secured to the dropped ceiling framework. A fire above a dropped ceiling often requires firefighters to pull down the ceiling in a hurry for quick access to the conflagration. Loose fixtures resting in the framework only by gravity may become unseated, swing down on their armorflex power cables, and hit the firefighters below. Binding the fixtures to the framework assures that if the framework must be pulled down, the fixture will come down with it and not become a pendulous swinging hazard to the firefighters.
To address fire safety, ceiling tiles made from mineral fibres, plastic, tin, composite, or fire-rated wood panels can be used within the construction to meet acceptable standards/ratings. Some tiles, in specific situations, can provide the needed additional resistance to meet the "time rating" required for various fire code, city ordinance, commercial, or other similar building construction regulations. Fire ratings for ceiling panels vary based on the materials used, the preparation of each panel, and the safety testing and third party evaluation done to determine where and how they can be safely installed. In the United Kingdom, tiles from certain manufacturers may be required to be clipped into the grid with special ceiling clips to provide a fire rating; there are special tiles designed for the underside of mezzanine floors however that can give a fire rating without being clipped.
Drop out ceilings have a further advantage since they can be mounted underneath fire sprinklers, thus hiding the sprinklers for a more attractive appearance. When they are installed under fire sprinklers, materials, applications, installation, and maintenance of drop out ceilings may be necessary to comply with fire safety regulations. [17]
Another advantage of a dropped ceiling is that the easily removed ceiling panels offer instant access to the plenum, which greatly simplifies repairs or alterations.
Wiring and piping installed behind traditional plaster or wallboard ceilings are extremely difficult to modify once the finished ceiling is in place. Wires must be fished through hollow spaces in the walls behind the finished ceiling, or the ceiling must be demolished for changes to wiring or piping to be made.
In contrast, the tiles and other parts of a dropped or stretch ceiling can be easily removed to allow access to the area above the grid to do any necessary wiring or plumbing modifications. In remodeling, nearly all components of the grid can be dismantled and reassembled elsewhere.
In office buildings, drop ceilings are often used in conjunction with hollow steel studs to construct small office spaces out of a much larger cavernous space. Wiring and other services are run through the open ceiling, down through the hollow stud walls, and to outlets in the work areas. If business needs change, the office spaces can be easily dismantled, with the overall cavernous space reconfigured with a different floor plan.
In older buildings that have had multiple renovations, a dropped ceiling has often been installed in one renovation and then subsequently removed in another since its installation having been an inexpensive fix to prolong the time between major renovations.
One disadvantage with this ceiling system is the reduced headroom. Clearance is required between the grid and any pipes or duct work above to install the ceiling tiles and light fixtures. In general, a minimum clearance of 100 to 200 millimetres (4 to 8 in) is often needed between the lowest obstruction and the level of the ceiling grid. A direct-mount grid may work for those who want the convenience of a dropped ceiling but have limited headroom. Stretch ceiling supports require less than 25 mm (1 in) of vertical space, and no space is required for tiles to be lifted out with a stretch ceiling, but a greater clearance space may be chosen to allow room for MEC or for aesthetic reasons.
Dropped ceilings generally conceal many of the functional and structural elements of a building, which creates an aesthetic paradigm that discourages the use of functional building systems as aesthetic design elements. Concealing such elements makes the complexity of today's advanced building technologies more difficult to appreciate. It is also more difficult to perform maintenance on or diagnose problems with the concealed systems. It is common practice in commercial and office settings to install drop ceilings in older buildings which were not designed for modern HVAC, electrical, or fire suppression systems in mind. These renovations are oftentimes criticized for covering up aesthetically appealing structural elements of older buildings.
As a renovation tool, dropped ceilings are a quick and inexpensive way to repair a ceiling and to reduce HVAC costs. Some materials may show their age quickly. For example, mineral fiber sags are damaged easily when handled and stain easily and permanently, but stretch ceiling, tin, and vinyl do not have such characteristics.
Owing to their popularity in the mid-20th century, many older drop ceilings incorporated asbestos for its insulating and fire-resistant properties. These can pose a serious health hazard to occupants and especially workers if the asbestos-containing elements are not properly removed.
A colocation center or "carrier hotel", is a type of data centre where equipment, space, and bandwidth are available for rental to retail customers. Colocation facilities provide space, power, cooling, and physical security for the server, storage, and networking equipment of other firms and also connect them to a variety of telecommunications and network service providers with a minimum of cost and complexity.
A floor is the bottom surface of a room or vehicle. Floors vary from simple dirt in a cave to many layered surfaces made with modern technology. Floors may be stone, wood, bamboo, metal or any other material that can support the expected load.
An electrician is a tradesperson specializing in electrical wiring of buildings, transmission lines, stationary machines, and related equipment. Electricians may be employed in the installation of new electrical components or the maintenance and repair of existing electrical infrastructure. Electricians may also specialize in wiring ships, airplanes, and other mobile platforms, as well as data and cable lines.
A ceiling is an overhead interior roof that covers the upper limits of a room. It is not generally considered a structural element, but a finished surface concealing the underside of the roof structure or the floor of a story above. Ceilings can be decorated to taste, and there are many examples of frescoes and artwork on ceilings, especially within religious buildings. A ceiling can also be the upper limit of a tunnel.
Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure.
Electrical wiring in the United Kingdom is commonly understood to be an electrical installation for operation by end users within domestic, commercial, industrial, and other buildings, and also in special installations and locations, such as marinas or caravan parks. It does not normally cover the transmission or distribution of electricity to them.
In telecommunications, structured cabling is building or campus cabling infrastructure that consists of a number of standardized smaller elements called subsystems. Structured cabling components include twisted pair and optical cabling, patch panels and patch cables.
A fly system, or theatrical rigging system, is a system of ropes, pulleys, counterweights and related devices within a theater that enables a stage crew to fly (hoist) quickly, quietly and safely components such as curtains, lights, scenery, stage effects and, sometimes, people. Systems are typically designed to fly components between clear view of the audience and out of view, into the large space, the fly loft, above the stage.
A raised floor provides an elevated structural floor above a solid substrate 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, Information technology data centers and 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 (1.2 m) 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.
An electrical junction box is an enclosure housing electrical connections. Junction boxes protect the electrical connections from the weather, as well as protecting people from accidental electric shocks.
Knob-and-tube wiring is an early standardized method of electrical wiring in buildings, in common use in North America from about 1880 to the 1930s. It consisted of single-insulated copper conductors run within wall or ceiling cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported along their length on nailed-down porcelain knob insulators. Where conductors entered a wiring device such as a lamp or switch, or were pulled into a wall, they were protected by flexible cloth insulating sleeving called loom. The first insulation was asphalt-saturated cotton cloth, then rubber became common. Wire splices in such installations were twisted together for good mechanical strength, then soldered and wrapped with rubber insulating tape and friction tape, or made inside metal junction boxes.
Ducts are conduits or passages used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. The needed airflows include, for example, supply air, return air, and exhaust air. Ducts commonly also deliver ventilation air as part of the supply air. As such, air ducts are one method of ensuring acceptable indoor air quality as well as thermal comfort.
A chilled beam is a type of radiation/convection HVAC system designed to heat and cool large buildings through the use of water. This method removes most of the zone sensible local heat gains and allows the flow rate of pre-conditioned air from the air handling unit to be reduced, lowering by 60% to 80% the ducted design airflow rate and the equipment capacity requirements. There are two types of chilled beams, a Passive Chilled Beam (PCB) and an Active Chilled Beam (ACB). They both consist of pipes of water (fin-and-tube) that pass through a heat exchanger contained in a case suspended from, or recessed in, the ceiling. As the beam cools the air around it, the air becomes denser and falls to the floor. It is replaced by warmer air moving up from below, causing a constant passive air movement called convection, to cool the room. The active beam consists of air duct connections, induction nozzles, hydronic heat transfer coils, supply outlets and induced air inlets. It contains an integral air supply that passes through nozzles, and induces air from the room to the cooling coil. For this reason, it has a better cooling capacity than the passive beam. Instead, the passive beam provides space cooling without the use of a fan and it is mainly done by convection. Passive beams can be either exposed or recessed. The passive approach can provide higher thermal comfort levels, while the active approach uses the momentum of ventilation air that enters at relatively high velocity to induce the circulation of room air through the unit. A chilled beam is similar in appearance to a VRF unit.
Audiovisual (AV) is electronic media possessing both a sound and a visual component, such as slide-tape presentations, films, television programs, corporate conferencing, church services, and live theater productions.
Cable management refers to management of electrical or optical cable in a cabinet or an installation. The term is used for products, workmanship or planning. Cables can easily become tangled, making them difficult to work with, sometimes resulting in devices accidentally becoming unplugged as one attempts to move a cable. Such cases are known as "cable spaghetti", and any kind of problem diagnosis and future updates to such enclosures could be very difficult.
Underfloor air distribution (UFAD) is an air distribution strategy for providing ventilation and space conditioning in buildings as part of the design of a HVAC system. UFAD systems use an underfloor supply plenum located between the structural concrete slab and a raised floor system to supply conditioned air to supply outlets, located at or near floor level within the occupied space. Air returns from the room at ceiling level or the maximum allowable height above the occupied zone.
A plenum space is a part of a building that can facilitate air circulation for heating and air conditioning systems, by providing pathways for either heated/conditioned or return airflows, usually at greater than atmospheric pressure. Space between the structural ceiling and the dropped ceiling or under a raised floor is typically considered plenum; however, some drop-ceiling designs create a tight seal that does not allow for airflow and therefore may not be considered a plenum air-handling space.
Copper has been used in electrical wiring since the invention of the electromagnet and the telegraph in the 1820s. The invention of the telephone in 1876 created further demand for copper wire as an electrical conductor.
An electrical conduit is a tube used to protect and route electrical wiring in a building or structure. Electrical conduit may be made of metal, plastic, fiber, or fired clay. Most conduit is rigid, but flexible conduit is used for some purposes.
On February 27, 1975, fire broke out at the New York Telephone Company switching center at 204 Second Avenue and Thirteenth Street in the East Village of Manhattan, New York City. At this time, the building contained central offices for connecting local customer telephone lines, as well as toll switching systems. The fire disrupted service for 175,000 customers, connected within the building through 105,000 service loops. It was the worst single service disaster suffered by any single Bell operating company in the 20th century.
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