A ceiling is a finish system applied over the inner or the bottom side of a roof or floor, compared with a flooring system which is applied to the outer or top side of a floor or roof. It is considered the upper limit of a room space.
Ceilings function as a ‘touching’ system, by being very close to the under side of a floor or roof system, or as a suspended system, little away from the floor or roof. Ceilings as a Touching system provide a cover, following the under side contour of a floor or roof. Whereas, suspended ceilings are designed to modulate the height values of space below and to cover space for various services.
Touching ceilings have no hanging or suspending members, so are more stable. Where small length hangers are required to accommodate conduits, wires etc., are of stiff materials only. Touching ceilings are made of preformed boards, wood planks, wood composite sheets, metal sheet forms, laminated paper composites, etc. fixed to a mono or bidirectional frame work of wood, sheet metal or rolled sections. The sections in turn may be hung through stiff hang fasteners from the roof structure such as joist soffit, beam or slab bottom. Touching ceilings are also like roof underside cladding or plaster. The cladding pieces are cut to accommodate the single, double or irregular curvature or slight variation in joints width. Plastered ceilings are deposits sprayed or trowel finished with suspended solids or foamed materials. The surface may be rendered for texturing or press hollowed for visual as well as acoustic needs.
Suspended ceilings leave a back-space of various depths. The spaces are left to accommodate pipes and ducts and to enforce a desired finished surface curvature. Such ceilings to modulate the space below often leave substantial ‘dead’ space above. Ceiling materials with high stiffness such as wood planks, glass, require equally rigid structure. Ceilings made from modulated pieces (panels, stripes), stretchable materials and thin materials can accommodate stresses and may not require rigid fixing. However ceilings subjected to upward and downward stresses as a result of increase and decrease in interior air pressures (such as auditoria), require both, compressive as well as tensile hangers.
Greeks used ceilings primarily to cover the roofing elements like, beams, joists, rafters and truss. The ceilings had coffered configurations. Romans created concrete vaults with coffers to reduce the weight. The Pantheon five rows of coffers in the dome and each coffer had receding flutes at the edge. In Gothic cathedrals under side of galleries, triforium etc. had flat ceilings. English medieval period the ceiling’s shape originated from the vaulting flutes terminating into complex circular patterns. Ceilings became extremely articulated in Renaissance period. Non secular buildings had ceilings in all rooms with guild work.
A tall ceiling with planes meeting at an angle, similar to a church is called a cathedral ceiling. A vaulted ceiling follows the vault geometry but accentuates it with many such repeated shapes. A concave or barrel-shaped ceiling is curved or rounded upward. A coffered ceiling is has recessed square or octagonal panels. A dropped ceiling is a touching ceiling. A cove ceiling uses a curved plaster transition between wall and ceiling, to create one continuous surface.
Ceilings are patterned for two distinct reasons: 1 to impose a design discipline, and, 2 to impose a texture. Patterns emerge from the natural grains (colour, variation, orientation) of the material, lay out of structural or natural joints, regimen forced by the sub structures, fasteners (screws, rivets), junctions of geometric and other shapes, etc. Patterns are created for providing texture to the surface of the ceiling. Textures either help highlight or subdue the joints, grains and shapes present in the ceiling. Textures accentuate or de-emphasize the light reflection, gloss etc. Textures, perforations and cavities enhance the sound absorption.