Meaning & use
joist
Last updated
Meaning
nouncountabletechnical
A long horizontal beam of wood or metal that supports a floor, ceiling, or roof.
Grammar: Takes a plural joists; usually refers to one of several parallel supports rather than a single main beam.
Patterns
- floor joist
- ceiling joist
- joist supporting something
The contractor replaced a cracked joist under the kitchen floor.
Before laying tile, check that each ceiling joist is level.
Word forms
| plural | joists |
|---|
Common combinations
- floor joist
- A loose floor joist can make the boards squeak upstairs.
- support a joist
- They added a post to support the joist above the stairwell.
- exposed joist
- The café left one exposed joist as a design feature.
Synonyms and how they differ
- beam
- A broader term for any long rigid support; a joist is a smaller parallel beam for floors, ceilings, or roofs.
- rafter
- Specifically supports a roof slope; joists are more often horizontal floor or ceiling supports.
- girder
- A larger main support, often steel, that carries joists or beams rather than acting as one of many parallel joists.
Commonly confused: joist or joint?
joist vs joint
Joint means a connection or point where parts meet; joist is a structural support and is spelled with i before s.
Practice
Many parallel wooden ___ run under the bedroom floor and hold it up.
Choose one answer.
Joists are the repeated horizontal supports beneath a floor. Rafters are roof members, studs are vertical wall supports, and girders are larger main beams.
Make it your own
Write a sentence using “joist”, then check it and compare it with the examples above.