Chapter 2 Flashcards
Functions of Finish Ceiling
- Controls diffusion of light and sound
- Prevents passage of sound vertically
- Control combustibility and passage of fire
- Part of distribution system for HVAC and lighting
- Accommodate sprinkler heads and loudspeakers
- Play a part in the visual expression of the room
- Ceilings can take variety of shapes and finishes to achieve its objectives including, flat, slope coffered, or vaulted
Exposed Structural and Mechanical Components
In many instances exposing the structural and mechanical components is appropriate
- Where appearance is not as important e.g. industrial or agricultural buildings
- Where structure is inherently attractive such as heavy timber construction or architectural concrete and steel
- Where exposed services add aesthetic appeal such as in restaurants
- Care and planning is required when systems are to be left exposed and it may increase cost
Tightly attached Ceiling
- Ceilings of different materials may be tightly attached to the underlying structural elements
- Special finishing arrangements need to be worked out for vertically projecting structural members such as beams
- Special consideration needs to be given for ducts, conduits, pipes and sprinkler heads that are below the ceiling
Suspended Ceiling
- Ceiling that is suspended on wires
It can conceal structure and services in space above called plenum - Ceiling can be flat even though the structure may be sloped
- Ceiling can serve as membrane fire protection for floor or roof structure above
- Can be made from variety of materials
Suspended Gyp and Plaster Ceiling
- Can be framed onto light gauge steel cee channels
- More complex shapes can be created with special framing members and by lathing e.g. auditoriums, theatres, and lobbies of public buildings
Suspended Acoustical Ceilings
- Made from fibrous materials in form of ties or panels referred to as acoustical ceilings because it is absorptive to sound
- Most economical type consists of lay-in-panels supported on exposed grid. Concealed grid is possible but require special panels
- most common in commercial construction
Noise Reduction Coefficient (NRC)
- Sound absorption is measured as Noise Reduction Coefficient (NRC). Higher the value better its absorption but more transmission and therefore needs sound proofing
Ceiling Attentuation Class (CAC)
Ceiling Attenuation Class (CAC) is the ceilings ability to reduce transmission through plenum
Articulation Class
Articulation Class is a measure of sound reflection and absorption related to speech clarity
Suspended Fire Resistance Rated Ceilings
- Suspended ceilings that are part of a fire resistance rated floor/ceiling or roof/ceiling assembly may be made of gypsum, plaster or lay-in panels and grid systems designed for that purpose
- Penetrations in such membrane ceilings must be detailed to maintain the FRR
- Lighting fixtures must be backed up with fire-resistive material
- Air conditioning grills must be isolated from the ducts that feed them by fire dampers
- Access panels must meet the requirements
Ceilings
- form a part of a system that accomodates lighting, partition attachments, supply- and return air grilles and diffusers, speakers, and other construction components
Ceiling classification
- how they are attached
- suspended
- attached directly
- part of the structure
Plenum
Space above the ceiling
Advantages of Suspended Acoustical Ceilings
- low cost
- fast installation
- sound control
- Flexibility
- Adaptability
- Easy Accessibilty to Plenum
Common Tile and Grid Sizes
- 24x24
- 24x48
- 20x60
Downward accessible system
- clip mounted to the framing
- pull a unit of two tiles loose, pivoting them at on end
Upward Accessible System
- two tiles are pushed up from a pivot point at one end and removed
- this is preferrablt to downward system
Seismic Restraint Detailing
Four Occupancy Categories
- according to how important the site is to post-earthquake recovery and how essential it is (i.e. hospitals and firehouses are in Category IV)
Six Seismic Design Categories
- A through F; A being the less restrictive and F being the most restrictive
- DEF have the most stringent criteria
Seimic Design Considerations
Design for compents: non structural walls, partitions, ceilings, cabinets, access floors, sprinkler pipes and bookcases among others
- the average weight of the ceiling system, including lighting and air terminalsshould be 2.5 lb per square foot
Coordination of Ceiling System Elements
Consider the selection and detailing of recessed lights, ductwork, sprinkler pping, fire alarm speakers, smoke detectors, drapery pockets, and other recessed items
Perimeter Isolation Joints
- should be used where the ceiling is adjacent to a strutural element or dissimliar partition
Control Joints
- Should be specified when ceiling dimension exceeds 50ft in either direction when perimeter Isolation joints are used or when a ceiling dimension extends 30ft if perimeter joints are not used
Abusive Resistant Ceilings
- designed to resist one or more of :
- environmental damage, humidity, atmospheric corrosion, surface moisture, contact with striking objects, frequent access to plenum, deliberate abuse, vandalism
- common for schools, jails, hospitals, and industrial plants
