What size plasterboard should I buy?

The trade uses the big boards because there are two of them and a van. In a house, with one person and a staircase, the calculation is different — and the honest answer is that fewer joints is better but only if you can get the board to the wall undamaged.

Step by step

1. Learn the standard sizes.2400 by 1200mm is the standard sheet. 1800 by 900mm is the common smaller size. Longer boards at 2700 and 3000mm are available for tall walls and for going floor to ceiling without a horizontal joint. Thicknesses are normally 9.5mm and 12.5mm, with 15mm for some fire and acoustic applications.
2. Measure the access, not just the wall.Front door, hallway width, the turn at the bottom of the stairs, the landing, the door into the room. A 2400 by 1200 board will not turn on most domestic landings. This is the constraint that actually decides the answer in a house.
3. Prefer the big boards if you can get them in.Fewer joints means less tape, less compound, less sanding and fewer places to crack. On a ground floor room with straight access, always use the full size.
4. Use 1800 by 900 upstairs, or when working alone.It exists precisely because it is the largest board one person can carry through a house without damaging it or themselves. The extra jointing is real work, but it is better than a broken board or a broken wall corner.
5. Consider a long board for a tall wall.Where the ceiling height is over 2400mm, a 2700 or 3000mm board hung vertically covers the height in one piece and eliminates a horizontal joint entirely. It is heavy and needs two people, but the finish is better.
6. Match thickness to the framing and the requirement.12.5mm is the domestic standard for walls and ceilings at 400 or 600mm centres. 9.5mm is used on close-centred framing and for some overboarding. Fire, acoustic and impact requirements may call for a thicker or a doubled board — there are dedicated guides on the board types and the fixing spec.
7. Order a couple of spare boards.Boards get damaged in transit and in handling, and a corner knocked off a tapered edge makes that board useless for a visible joint. Two spares on a room's worth of boarding is cheap insurance and saves a second delivery.
8. Have them delivered, and think about where.Plasterboard is heavy, fragile and awkward, and it is the one board that should essentially always be delivered rather than carried home. Ask whether the driver will take it inside or only to the kerb.

Tips

• Note the 40mm difference from a standard board sheet — plasterboard is 2400 by 1200 where plywood and MDF are 2440 by 1220. It matters where the two have to line up in one plane.
• Working out the number of boards: divide the wall area by the board area, then add 15 to 20 per cent, because plasterboard generates more offcut waste than most materials once you have cut round openings.
• If you are boarding a ceiling, use the smaller boards even if you can get the big ones in. A 2400 by 1200 board overhead is genuinely difficult for two people and impossible for one.
• Check the edge profile as well as the size. Tapered edge for taping and jointing, square edge for skimming — it is a separate decision from the sheet size and it is easy to miss when ordering.

Common mistakes

• Ordering full-size boards for an upstairs room without checking the stairs — The boards arrive, will not go up, and either get bent round the turn — which cracks them — or get cut down, which wastes the advantage you paid for. Measure the route first.
• Ordering exactly the calculated number of boards — Damage in transit and handling is normal, cutting round openings produces unusable offcuts, and running out means a second delivery. Order a couple over.
• Choosing the size before the edge profile — The edge profile decides the finishing method and matters more. Establish tapered or square edge first, then pick the size.

Questions people ask