How many plasterboard sheets do I need for a partition? A materials guide

A plasterboard partition goes up faster than a traditional masonry one, but that doesn't mean it's calculated "roughly": mixing up the wrong board type with the room, or running short of framing, forces the job to stop halfway through the build.

Which type of board to use in each room

Not all plasterboard is the same, and choosing the wrong one can be a serious problem, not just an aesthetic one:

• Standard (type A) — general use in dry areas: bedrooms, living rooms, corridors. Usual thickness 13 mm.
• Moisture-resistant (type H, green) — for bathrooms, kitchens and utility rooms. Note: it isn't waterproof on its own; in the direct splash zone of the shower a waterproofing membrane is still needed before tiling.
• Fire-resistant (type F, pink) — mandatory under the CTE for separations of garages, plant rooms and stairwells. The real fire resistance (EI30, EI60...) depends on the complete approved system, not just on using this board on its own.
• Reinforced / high density — takes more hanging weight (bookcases, tall furniture) without having to hit a stud at each fixing. Even so, for really heavy loads (wall-hung sanitaryware, a large TV) it is still safer to screw into the stud.
• Curved / flexible — for arches or wavy walls; it is usually bent in two layers to gain rigidity after curving.

How much board to buy over the real area

The standard margin is 10% for cuts and offcuts over the partition area (12% for curved board, because of the breakages inherent in curving). For a 15 m² partition: 15 × 1.10 = 16.5 m² of board to buy. This is the same calculation the PresupuestoYa calculator applies automatically for the Drywaller trade.

Framing: channel, stud and spacing

• Channel (horizontal profile): fixed to floor and ceiling, with a 5% margin for joints. The width (48, 70 or 100 mm) must match that of the stud it will house — the wider, the more sound insulation and the more space inside to run services.
• Stud (vertical profile): inserted into the channels every 40 or 60 cm, with a 10% margin for cuts. Use 40 cm spacing on partitions with a single layer of board or more mechanical demand; 60 cm is enough with double boards or linings with hardly any load.

Insulation between studs

• Rock wool: better acoustic and fire performance (non-combustible); preferable in partitions with acoustic requirements between homes.
• Glass wool: cheaper, good thermal performance, enough for interior partitioning with no special acoustic requirement.

Both carry a 5% margin for offcuts over the area to be filled.

Complete worked example

For a 15 m² partition with standard single 13 mm board, studs every 40 cm and 70 mm rock wool fill:

1. Board: 15 m² × 1.10 = 16.5 m² to buy
2. Insulation: 15 m² × 1.05 = 15.75 m² of rock wool
3. Channel and stud: calculated over the perimeter and the total length of studs needed, with their corresponding margin

Frequently asked questions

Is moisture-resistant board already waterproof for the shower? No. It resists the ambient humidity of the bathroom well, but in the direct splash zone a waterproofing membrane is still needed before tiling.

What stud spacing should I use? 40 cm if the partition has a single board or has more mechanical demand; 60 cm is enough with double board or linings with no load.

What insulation do I choose if the partition faces a noisy area? Rock wool: its higher density compared with glass wool improves insulation against airborne noise.

Conclusion

Getting the board type right for the room and calculating framing and insulation along with the cutting margin is what separates a well-quoted plasterboard partition from one that forces a second order halfway through the build. Automating it gives a clear breakdown, ready for the client.