Drywall Calculator | Plasterboard Calculator UK 2025

The standard plasterboard size in the UK is 2400mm x 1200mm (8ft x 4ft) with 12.5mm thickness for walls. This size is suitable for standard 2.4m ceiling heights and fits between studs at 600mm centres. For ceilings, 9.5mm thickness is commonly used for overlays, while 12.5mm or 15mm is recommended for new installations.

For a standard 2400mm x 1200mm plasterboard sheet fixed to timber studs at 600mm centres, you typically need 40-50 screws. Screws should be placed at 150mm centres along edges and 300mm centres in the field (middle area). For ceilings, use closer spacings of 150mm throughout due to gravity loads.

Dot and dab (direct bonding) uses adhesive blobs to fix plasterboard directly to masonry walls. It's faster and requires no framework but needs relatively flat walls. Screw fixing uses metal or timber studs, creating a cavity for insulation and services, and works on any wall condition. Screw fixing is required for fire-rated or acoustic partitions.

For simple rectangular rooms, allow 10% waste. For rooms with many openings (doors, windows) or complex shapes, allow 15%. Professional contractors often allow 10-15% as standard. Waste comes from cutting around openings, damaged boards, and offcuts too small to use.

Yes, moisture resistant (MR) plasterboard should be used in bathrooms, shower rooms, kitchens, and utility rooms where humidity is high. MR board (often green-faced) has water-repellent additives in the core. For shower enclosures, consider cement backer board or tile backer board which offers even better moisture protection.

For ceilings in the UK, 12.5mm plasterboard is standard when joists are at 450mm centres or less. For joists at 600mm centres, use 15mm boards to prevent sagging. 9.5mm board can be used for re-covering existing ceilings but should never be used alone for new ceiling installations. Always check Building Regulations for fire and acoustic requirements.

For a stud wall: 1) Measure length x height to get total area in m2. 2) Subtract door openings (standard UK internal door = 1.98m x 0.76m = 1.5m2). 3) Add 10-15% waste. 4) Divide by board area (standard board = 2.88m2). 5) Double the quantity as stud walls are lined both sides. Don't forget you'll also need metal or timber studs, head and sole plates.

Standard 12.5mm plasterboard provides 30 minutes fire resistance when fixed to one side of a timber stud partition. For 60 minutes fire resistance, use two layers of 12.5mm or one layer of 15mm Fireline board. For 90-120 minutes, specialist fire-rated systems from British Gypsum or Knauf are required. Always check Building Regulations Approved Document B for specific requirements.