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Project guide

How much plasterboard do I need?

Each standard 2400 x 1200mm sheet covers 2.88 m². Divide your area by that, add 10% for cuts, then work out the screws, tape and plaster to go with it.

Updated Based on manufacturer guidance, sources below

The short answer

Sheets = area to board / 2.88, plus 10% for cuts, rounded up. A 4 x 3.5m room with 2.4m walls and the ceiling boarded is 50 m², which is 20 sheets of 12.5mm board, about 640 drywall screws, 1 roll of scrim and 6 bags of Multi-Finish.

The formula

  • Area (m²) = total wall length x wall height + ceiling area
  • Sheets = area / 2.88 x 1.1, rounded up
  • Screws = 12 per m² on walls (300mm centres) + 15 per m² on ceilings (230mm centres)
  • Multi-Finish bags (25kg) = area x 1.1 / 10

Worked example

A 4 x 3.5m room, 2.4m high, walls and ceiling, screwed to timber:

  • Walls: 15m x 2.4m = 36 m². Ceiling: 14 m². Total 50 m²
  • Sheets: 50 / 2.88 = 17.4, plus 10% = 19.1, so 20 sheets
  • Screws: 36 x 12 + 14 x 15 = 642, so one box of 1000 x 42mm
  • Multi-Finish: 50 x 1.1 / 10 = 5.5, so 6 bags
  • Scrim: about 45m of joints, so 1 roll of 90m

Work it out for your job

Change the measurements and the quantities update straight away.

Add each wall together. A 4 x 3.5m room is 15m.
Area to board
50 m²
Boards (+10%)
20 sheets

Your list

  • 2012.5mm plasterboard, 2400 x 1200mm
  • 142mm drywall screws, boxes of 1000 (~642 screws)
  • 1Scrim tape, 90m rolls
  • 6Multi-Finish plaster, 25kg bags
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Materials checklist

  • 12.5mm plasterboard, 2400 x 1200mmThe standard board for walls and ceilings. Use moisture-resistant board in bathrooms.
  • 42mm drywall screws12.5mm board plus at least 25mm into the timber, as British Gypsum specifies.
  • Scrim tapeSelf-adhesive mesh over every joint and internal corner, so the skim does not crack.
  • Multi-Finish plasterA 2mm skim over the boards. Each 25kg bag covers about 10 m².
  • Metal corner beadProtects and straightens outside corners such as chimney breasts.
  • Dot & dab adhesive (masonry walls)About one 25kg bag per 2 boards, instead of screws.

You'll also need

  • Board lifter or a helper for ceilings
  • Plasterboard saw or knife and a rasp
  • Plastering trowel, hawk, mixing paddle and buckets
  • Drill/driver with a drywall screw setter
  • Dust mask and safety glasses

Step by step

  1. Measure the areaAdd the lengths of the walls you are boarding, multiply by the height and add the ceiling area.
  2. Count the sheetsDivide by 2.88 m² per sheet, add 10% for cuts, and round up.
  3. Choose the fixingScrew to timber at 300mm centres on walls and 230mm on ceilings, or dot & dab onto brick and block.
  4. Tape the jointsRun scrim tape over every joint and internal corner before skimming.
  5. SkimApply Multi-Finish in two coats to about 2mm. Allow 10 m² per bag plus 10%.

Tips from the manufacturers

  • Use 42mm screws with 12.5mm board. British Gypsum asks for at least 25mm of screw in the timber; 32mm screws only give about 19.5mm.
  • Screw centres matter: 300mm on walls and 230mm on ceilings (British Gypsum Site Book). That is roughly 12 and 15 screws per m².
  • Stagger the board joints so they do not line up across the wall, and keep screws back from the board edges as the British Gypsum Site Book describes.
  • Board ceilings first, then walls, so the wall boards support the ceiling edges.

Mistakes to avoid

  • Using 32mm screws because they came in the box: they do not reach far enough into the stud.
  • Forgetting the ceiling, or the window reveals, when measuring.
  • Skipping scrim tape on joints, which leads to cracks in the skim.
  • Ordering exact sheet numbers with no allowance for cuts around doors and windows.

Frequently asked questions

How many m² is a sheet of plasterboard?

A standard 2400 x 1200mm sheet covers 2.88 m². Smaller 1800 x 900mm sheets cover 1.62 m² and are easier to handle on your own.

How many plasterboard sheets for a 4 x 3.5m room?

With 2.4m walls and the ceiling, that is 50 m², or 20 sheets including 10% for cuts. Walls only is 36 m², or 14 sheets.

How many screws per sheet of plasterboard?

At British Gypsum spacings, about 35 screws per 2.88 m² sheet on walls (12 per m²) and about 43 on ceilings (15 per m²).

What length screws for 12.5mm plasterboard?

Use 42mm drywall screws. British Gypsum asks for at least 25mm of screw into the timber, plus the board thickness.

How much adhesive for dot and dab?

Allow about one 25kg bag of plasterboard adhesive such as Gyproc DriWall for every two boards.

Sources

Quantities are estimates for typical jobs, using the coverage figures above. Products vary, so check the data sheet for the product you buy, and talk to a professional for structural, electrical or gas work. SmartBuild is independent and not affiliated with any of the manufacturers listed.

How much plaster do I need to skim a room?A finish skim is about 2mm thick. British Gypsum says a 25kg bag of Multi-Finish covers about 10 m² at that thickness. Stud wall materials list: what do I need?A timber stud partition is CLS studs at 400mm centres between a head and sole plate, boarded both sides. Here is everything on the list and how much of each. How much paint do I need for a room?Measure the walls, take off doors and windows, multiply by the number of coats and divide by 12. Here is the rule, a worked example and a calculator that does it for you.

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