What is it?
The ceiling is the finished underside of the structure above (the floor or roof deck of the storey above), usually plasterboard fixed to joists or battens, or hung independently of the structure on its own suspended grid. It's the overhead surface of a room, the counterpart to the floor finish underfoot.
What does it do?
Finished overhead surface It gives the room a flat, decorated surface overhead, concealing the structural joists or deck and whatever services run above them.
Concealing and protecting services Cables, pipework and ductwork typically run in the void above the ceiling, hidden from view and protected from the room below. A suspended ceiling in particular is chosen specifically to keep that void accessible for maintenance.
It is also the substrate for any spot lights or sensors that can be recessed into the plasterboard ceiling.
Fire and acoustic separation Together with the floor structure above it, the ceiling forms part of the fire and acoustic separation between storeys, which is why its board thickness, layers and fixing are specified in accordance with manufacturers' tested systems.
Insulation can be concealed in the ceiling void to improve its fire and acoustic performance.
Where is it used?
Every room, in one of two basic forms: plasterboard fixed directly to the joists or to battens below them, or a ceiling hung independently of the structure. That's either a plain suspended/independent ceiling for extra acoustic separation, or a grid-and-tile suspended ceiling where the void above needs to stay easily accessible, the usual choice in offices and other commercial fit-outs.
Types
How a ceiling is actually built depends on what it needs to do beyond just looking flat and finished.
Direct-fix plasterboard
Plasterboard screwed straight to the underside of the joists, or to battens fixed across them. The simplest and most common domestic ceiling.
Independent (suspended) ceiling
A separate plasterboard ceiling hung from its own metal or timber frame below the structure. The height of the ceiling is adjustable and results in a void between the structure and the boards that enclose the ceiling. This can be used for services and for acoustic separation between storeys.
Grid and tile suspended ceiling
Lightweight tiles dropped into a suspended metal grid, leaving the void above freely accessible. The standard commercial/office ceiling, chosen for how easily services above it can be reached.
How to specify
Board type, thickness and number of layers are set by the fire and acoustic separation the floor above it needs to achieve as a whole, usually specified as a tested system rather than chosen layer by layer. Where a partition wall meets the ceiling, its head detail has to be decided. Usually the partition wall will go up to the slab or structure above, and the ceiling stops and starts either side of it.
Other considerations
Any penetration through a fire- or acoustic-rated ceiling (a downlight, a pipe, a duct) needs fire-stopping or an acoustic hood around it, or it becomes the weak point in what the ceiling was specified to achieve. Where a suspended ceiling is used for services access, coordinate its height against everything that needs to run in the void above it before the grid goes in.
Interacting elements
- Deflection head: the wall's own head detail has to coordinate with where the ceiling stops and how it's fixed
- Plasterboard: the board the ceiling itself is usually built from
- Acoustic insulation: often added within the ceiling void for extra separation between storeys
- Slab: the structural floor above that the ceiling is fixed to or suspended beneath