Parts of a Ceiling – Joists, Drywall and the Drop Grid

All 9 parts on the diagram

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Start here: 5 main parts 5

Ceiling joist One of the parallel timbers that carry the ceiling finish.
Gypsum board (drywall) A sheet of gypsum faced with paper, fastened to the joists.
Ceiling insulation It lies between the joists, over the heated rooms.
Ceiling tile (panel) A light panel that simply drops into the grid.
Main runner The long bars of the grid; the hangers hold them up.

A framed ceiling 1

Crown molding (ceiling molding) Trim fixed where an inside wall meets the ceiling.

A suspended ceiling 3

Cross tee The short bars that span between the main runners.
Hanger wire The grid hangs on wires from the structure overhead.
Plenum The space above a dropped ceiling, where pipes, wires and ducts run.

How this list was compiled: Read 2026-09-30; a name is kept only where two of these use it. (1) L. O. Anderson and O. C. Heyer, Wood-Frame House Construction, US Department of Agriculture, Agriculture Handbook No. 73 (1955), https://archive.org/details/WoodFrameHouseConstruction : ceiling joists support ceiling finishes; gypsum board is a sheet material of a gypsum filler faced with paper; ceiling insulation; ceiling moldings are placed at the junction of the wall and the ceiling; the strongback that lines up ceiling joists. (2) Canada Mortgage and Housing Corporation, Canadian Wood-Frame House Construction, https://archive.org/details/CANADIANWOODFRAMEHOUSECONSTRUCTION : ceiling joists, gypsum board and drywall, ceiling insulation. (3) US Naval Education and Training Command, Builder 3 & 2 (1981), https://archive.org/details/ERIC_ED210471 : ceiling joists, gypsum board, ceiling tile, and its section on a suspended acoustical ceiling (wall angles, suspension wires, main tees, cross tees, acoustical panels). (4) US National Bureau of Standards, A Glossary of Housing Terms, https://archive.org/details/glossaryofhousin91subc : joist, gypsum board. (5) Unified Facilities Guide Specification UFGS-09 51 00, Acoustical Ceilings, https://www.wbdg.org/FFC/DOD/UFGS/UFGS%2009%2051%2000.pdf : main runners, hanger wires, wall molding, ceiling tile, acoustical units, ceiling plenum. (6) A ceiling maker's estimating program manual, https://archive.org/details/manualzilla-id-5770479 : main runners, cross tees, hangers, panels and tiles, plenum depth. (7) Wikipedia, Dropped ceiling (a gridwork of metal channels suspended on wires; each cell filled with ceiling tiles or panels that just drop into the grid; the plenum space above, for piping, wiring and ductwork), Crown molding (fitted where an interior wall meets the ceiling), Ceiling. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work

How it works

Most ceilings are one of two kinds: board fixed to the joists of the floor or roof above, or a grid of tiles hung below them. These are the names of the pieces in each.

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A framed ceiling

Ceiling joists span from wall to wall. Gypsum board, also called drywall, is fastened to their undersides and its joints are taped. Insulation lies between the joists when the space above is not heated. Crown molding trims the corner where the ceiling meets the wall.

A suspended ceiling

Main runners hang on hanger wires from the structure overhead. Cross tees span between the runners to make a grid, and a ceiling tile drops into each opening. The space above the tiles is the plenum, where pipes, wiring and ducts run.

A suspended ceiling is also called a drop ceiling, a dropped ceiling or a T-bar ceiling.

Questions and answers

What are the parts of a ceiling called?

A framed ceiling has ceiling joists, gypsum board fastened under them, insulation between them and often crown molding at the walls. A suspended ceiling has main runners, cross tees, hanger wires and ceiling tiles, with the plenum above.

What are the parts of a drop ceiling grid?

Main runners are the long bars, hung from above on hanger wires. Cross tees are the shorter bars that span between them. A strip fixed to the wall carries the edge of the grid, and a tile drops into each opening.

What is the space above a drop ceiling called?

The plenum. It is the gap between the tiles and the floor or roof structure overhead. Pipes, wiring and ductwork run through it, and a tile lifts out to reach them.

What is the trim between the wall and the ceiling called?

Crown molding, or ceiling molding. It is fixed along the corner where an inside wall meets the ceiling, for looks or to cover the joint between the two boards.