When we were boarding out our loft conversion a few years ago, I made a trip to the merchant that I wish I could take back. I loaded the van with 20 boards of standard 12.5mm grey-faced plasterboard for everything - walls, ceiling, and the bathroom partition. The merchant had briefly mentioned green-faced boards but I had dismissed it as an upsell.
The bathroom partition went up fine. But when I tiled it six months later and the grout started showing signs of damp staining within a year, I realised the grey-faced standard board had absorbed moisture and the paint coat had not been enough protection. I had to strip and re-board the whole partition with proper moisture-resistant board before retiling.
The cost of the right board upfront was far less than the cost of stripping, re-boarding and retiling. Here is how to choose correctly from the start.
Standard board sizes
The core sizes you will find at UK builders merchants:
| Size | Area per board | Common use |
|---|---|---|
| 2400 x 1200mm (8 x 4ft) | 2.88 m2 | Standard walls - the UK default |
| 2400 x 900mm | 2.16 m2 | Walls, ceilings, narrow sections |
| 2700 x 1200mm | 3.24 m2 | High ceilings, fewer horizontal joints |
| 3000 x 1200mm | 3.60 m2 | High ceilings and commercial work |
| 1200 x 900mm | 1.08 m2 | Small areas, patches, repairs |
The 2400 x 1200mm board is the standard in UK residential construction. For rooms with ceiling heights up to 2.4m, you can run these boards vertically and cover the full wall height in a single board. For ceiling heights above 2.4m, the wider boards (2700 or 3000mm) reduce the number of horizontal joints.
Thickness: the key numbers
| Thickness | Weight (2400x1200) | Best use |
|---|---|---|
| 9.5mm | approx 18kg | Ceilings, lightweight partitions |
| 12.5mm | approx 25kg | Standard walls - the default |
| 15mm | approx 30-32kg | Enhanced fire and acoustic applications |
12.5mm is the right default for walls. It has better impact resistance than 9.5mm (important in hallways and kids' rooms), better acoustic performance, and a better fire rating.
9.5mm is the right choice for ceilings. A full 2400 x 1200mm board at 12.5mm weighs 25kg. Holding that flat against the ceiling joists while driving screws is hard work. 9.5mm boards weigh 18kg - a meaningful reduction when you are working overhead for hours.
15mm is specified where Building Regulations require it - party walls with improved acoustic performance, escape routes in HMOs, or walls adjacent to garages or boiler rooms. Do not use it as a general upgrade unless you have a specific reason - the extra weight makes handling harder and it costs more.
Board types and face colours
The face colour coding used in the UK:
Standard (ivory or grey face) - General-purpose plasterboard for walls and ceilings in dry conditions. Correct for most bedrooms, living rooms, hallways and dry utility spaces.
Moisture-resistant (green face, often labelled MR) - Enhanced moisture resistance for humid rooms. Recommended for kitchens and bathrooms where steam and condensation occur. Not waterproof - it resists incidental moisture but is not a tile backing board for wet areas.
Fire-resistant (pink or red face, often labelled FR) - Enhanced fire performance for legally required applications. Used in integral garages adjacent to living spaces, around boiler rooms and plant rooms, in flat conversions, and in other fire-compartment situations defined by Building Regulations.
Acoustic (heavy, dense boards) - Heavier than standard boards of the same thickness. Used to reduce sound transmission through party walls or between rooms. Often specified as double-layer boarding (two layers of 12.5mm rather than one layer of 15mm) for the best acoustic result.
Insulated (PIR-bonded or EPS-bonded) - Rigid insulation foam bonded to plasterboard. Used for drylining external walls to add insulation. Various insulation thicknesses available, typically 25-100mm of PIR.
Where to use each type
| Location | Board type | Thickness |
|---|---|---|
| Bedroom or living room wall | Standard | 12.5mm |
| Bedroom or living room ceiling | Standard | 9.5mm |
| Kitchen wall | MR (green) | 12.5mm |
| Bathroom wall (not directly wet) | MR (green) | 12.5mm |
| Behind bath or shower (tiling over) | Tile backing board | n/a |
| Integral garage / garage conversion | FR (pink) | 12.5mm |
| Party wall between houses | Acoustic or double-layer | 12.5mm x 2 |
| Loft conversion ceiling/walls | Standard or FR (check regs) | 12.5mm |
| External wall insulation (drylining) | Insulated PIR board | 12.5mm + insulation |
Tapered edge vs square edge
Tapered edge (most common): The long edges of the board are slightly bevelled back from the face. This creates a shallow recess at board joints that you fill with jointing compound and tape, then feather out. The result is a perfectly flat surface without skim-coating. Used for dry-lined (tape and joint) finishes.
Square edge: All edges are at right angles. The whole surface is covered with scrim tape at joints and then receives a full skim coat of finishing plaster. Used when you want a traditional two-coat plaster finish.
Most modern domestic boarding uses tapered-edge boards with a tape and joint or skim finish. If your plasterer is skimming the whole surface, either edge type works - ask which they prefer.
How many boards do I need?
Once you know which type and size you need, the calculation is straightforward:
- Calculate total area (all walls + ceiling if boarding both)
- Deduct all opening areas (doors, windows, any fixed features)
- Add 10% wastage
- Divide by board area (2.88 m2 for standard 2400x1200mm)
- Round up to whole boards
Our Plasterboard Calculator handles multiple walls and rooms in a single calculation, including all your opening deductions and giving you the total board count with fixings.
My tips on choosing and buying plasterboard
Ask the merchant what they stock before assuming. Large boards (2700 and 3000mm) are not stocked everywhere - some merchants order on demand, which adds lead time. Confirm availability before you plan your schedule around them.
Check how you will get them home. 2400 x 1200mm boards are awkward to transport. They just about fit in a standard Transit van laid flat. They do not go in hatchbacks or estate cars without folding seats and risking damage. Factor in delivery cost if you do not have a suitable vehicle.
Store flat and off the ground. Boards stored on their edges or leaning against walls can bow. Stored flat on a level surface, they stay perfectly straight. Cover with polythene to protect from damp during storage.
Buy extra green-face board if in doubt. If a room might see any humidity at all - a utility room, a downstairs cloakroom, a basement room - use green-face board. The cost difference versus standard board is small and you will not regret the extra moisture resistance.
Use the Plasterboard Calculator to get accurate board counts before ordering.