What plasterboard do I need for a ceiling?
Ceilings are harder on plasterboard than walls, because the board hangs from the joists. Getting the thickness and fixings right stops sagging and cracked joints later.
The usual thickness
12.5 mm is the usual board for ceilings. Thinner 9.5 mm board is only suitable where the joists are closer together. Each manufacturer publishes the maximum joist spacing for each board, so check the data sheet against your joists before ordering.
When you need a special board
- Fire-rated board, or two layers, where building regulations need fire separation, such as under a room above an integral garage or in a loft conversion
- Moisture-resistant board in bathrooms and kitchens
- Acoustic board, or two layers with insulation between the joists, to cut noise from the room above
Overboarding an old ceiling
Overboarding means fixing new board over an existing ceiling, often lath and plaster or damaged board. The old ceiling must be sound and firmly fixed. Your screws need to be long enough to pass through both layers and well into the joists, so allow for the old ceiling’s thickness when you order them.
Fixings and finishing
- Drywall screws to suit the board and the number of layers
- Jointing tape and filler, or scrim and multi-finish plaster
- Angle beads or stop beads where needed
- Board lifter or props if you’re fixing on your own
This is a general guide, not a specification. Your builder, architect, building control or the manufacturer will confirm exactly what your project needs.
Get it priced
Use the plasterboard calculator for the sheet count, then send your list for a quote.
Common questions
Is 9.5 mm plasterboard OK for a ceiling?
Only where the joists are close enough together for that board. Most ceilings use 12.5 mm. Check the manufacturer’s maximum joist spacing for the board you’re buying.
Do I need fire-rated plasterboard on a ceiling?
Sometimes. Ceilings that form fire separation, for example below a room over an integral garage, usually need fire-rated board or extra layers. Building control will confirm what your project needs.