Dropped ceiling
This invention provided suspended ceiling construction in which access may readily be obtained at any desired location.
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.
The acoustic performance of suspended ceilings has improved dramatically over the years, with enhanced sound absorption and attenuation.
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.
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.
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.
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.
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.
Loose fixtures resting in the framework only by gravity may become unseated, swing down on their armorflex power cables, and hit the firefighters below.
To address fire safety, ceiling tiles made from mineral fibres (asbestos), 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.
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.
Wiring and other services are run through the open ceiling, down through the hollow stud walls, and to outlets in the work areas.
Clearance is required between the grid and any pipes or duct work above to install the ceiling tiles and light fixtures.
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.
Owing to their popularity in the mid-20th century, many older drop ceilings incorporated asbestos for its insulating and fire-resistant properties.
