Types of ceiling
‘A part of a building which encloses and is exposed overhead in a room, protected shaft or circulation space. (The soffit of a rooflight is included as part of the surface of the ceiling, but not the frame. An upstand below a rooflight would be considered as a wall.)’
Ceilings help create enclosure of and separation between spaces, they help to control the diffusion of light and sound around a room, and help prevent the passage of sound between rooms. They have fire resistant properties and may also accommodate building services such as vents, lighting, sprinkler heads and so on, as well as being able to conceal other services such as ducts, pipes and wiring.
 Types of ceiling
 Exposed ceilings
In some buildings, it is possible to omit a 'finished' ceiling completely and simply expose the structural and mechanical components of the building to the interior. This offers the advantages of economy and ease of access for maintenance, and can also expose the thermal mass of the building. The thermal mass of exposed ceilings can be further exploited by the installation of heating or cooling elements such as chilled beams.
If well designed and installed, roof structures and floor structures can be aesthetically pleasing if left exposed ot the space below, such as timber beams, concrete slabs, space trusses and so on. The mechanical elements at ceiling level can also create an attractive aesthetic effect.
A permeable suspended ceiling such as an open lattice is sometimes suspended below exposed ceilings. This can be an inexpensive and visually dramatic way of partially concealing services without preventing the movement of air. This technique is often used in retail spaces.
 Tightly-attached ceilings
Ceilings made of gypsum, plasterboard, tongued and grooved timber and so on, may be attached tightly to timber joists or rafters, steel joists or concrete slabs. Careful detailing is required where beams or other obstructions protrude through the plane of the ceiling, such as vents, conduits, pipes, sprinkler heads and so on.
Suspended ceilings (sometimes referred to as dropped ceilings or false ceilings) are secondary ceilings suspended from the structure above (typically a floor or roof slab), creating a void between the underside of the slab and the top of the suspended ceiling.
As well as concealing the underside of the slab, this void can provide a useful space for the distribution of heating, ventilation and air conditioning (HVAC) services and plumbing and wiring services, as well as providing a platform for the installation of speakers, light fittings, wireless antenna, CCTV, fire and smoke detectors, motion detectors, sprinklers and so on. It can also provide an air ‘plenum’, in which the void itself forms a pressurised ‘duct’ to supply air to, or extract it from the occupied space below.
For more information see Suspending ceilings.
 Interstitial space
Interstitial spaces, such as interstitial ceilings allow for a larger space to be located between regular-use floors. They generally include an access walkway, and have a low height. They are commonly used in buildings such as hospitals and laboratories that have complex services which may include:
- Air-conditioning ducts.
- Water and waste pipework.
- Electrical and communications wiring.
- Fuel gas lines.
- Compressed air lines.
- Chilled water.
- Vacuum pipework.
- Chemical waste pipework.
As ducts and pipework can occupy a significant amount of space, often require continual maintenance and are subject to frequent change, interstitial ceilings can allow for maintenance and updating work to be carried out without interruption of activities in the spaces above and below.
 Acoustical ceilings
Acoustic ceilings tend to be made from fibrous materials that absorb sound energy, unlike plaster and gypsum ceilings. They do not necessarily reduce the transmission of sound between spaces, rather they reduce the amount that reflects back into the space and so can be used to tailor the acoustic character of a space.
The sound absorption performance of a ceiling material is expressed in terms of its noise reduction coefficient (NRC). An NRC of 0.85 means that a ceiling material absorbs 85% of the sound that reaches it, and reflects 15% back into the room. NRCs for most acoustical ceilings range from 0.5 to 0.9, compared to values below 0.10 for plaster and gypsum ceiling board materials.
Where acoustic privacy is required, heavier ceiling materials such as plaster or gypsum board are more effective.
 Radiant chilled ceilings
Radiant chilled ceilings typically incorporate a network of chilled water coils in ceiling panels with insulation above. In some systems, pipework may be incorporated into plasterboard, but this is less efficient as plaster is an insulator. The ceiling surface then cools the occupied space by both radiation and convection. This provides even temperatures throughout the space and avoids draughts.
Very little space is required for chilled ceilings, which may be installed with a depth of just 100mm. In some systems, small bore cooling coils can be embedded in plaster ceiling finishes themselves.
Where this network is designed as a series of panels suspended from the ceiling they may be described as ‘rafts’ or ‘sails’.
See Chilled ceiling for more information.
 Convective chilled ceilings
Convective chilled ceilings are a variation on radiant chilled ceilings, in which the network of chilled water pipes incorporates fins, increasing the proportion of cooling that is provided by convection.
Integrated service modules (ISM), sometimes referred to as multi-service chilled beams (MSCB), are a form of factory assembled modular chilled beam that incorporate other services in addition to cooling, such as lighting, speakers, sprinklers, passive Infrared (PIR) sensors and so on.
See integrated service module for more information.
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