What Is Gypsum Board? (And How It Differs from Plasterboard)

What is gypsum?

Gypsum is a soft mineral, chemically known as calcium sulphate dihydrate. The formula is CaSO₄·2H₂O. That "2H₂O" is important because it means gypsum contains two water molecules for every molecule of calcium sulphate, locked into the crystal structure.

When you heat gypsum above 100°C, that water is released as steam. This is why gypsum board is fire-resistant. The steam absorbs heat and slows down the temperature rise on the unexposed side of the wall or ceiling. A 12.5mm gypsum board gives 30 minutes fire resistance because it takes that long for the gypsum to fully dehydrate and lose its protective effect.

Where does gypsum come from?

In the UK, gypsum is either mined from natural deposits (Sussex, Cumbria, Nottinghamshire) or produced as flue gas desulphurisation (FGD) gypsum, a byproduct of coal power stations. FGD gypsum is chemically identical to natural gypsum. About 40% of UK gypsum board uses recycled FGD gypsum.

Imported gypsum comes from Spain, Poland, and Germany. The UK gypsum industry processes around 2 million tonnes per year.

How is gypsum board manufactured?

Gypsum board manufacturing is a continuous process. Here's the simplified version:

1. Calcination. Raw gypsum is heated to 150-180°C to drive off some of the water, converting it to hemihydrate (plaster of Paris). This is the active ingredient that sets when water is added back.
2. Mixing. The calcined gypsum is mixed with water, additives (for fire resistance, water resistance, or setting time), and sometimes fibreglass or vermiculite for specialist boards.
3. Forming. The wet slurry is poured onto a moving sheet of heavy paper. A second sheet of paper is laid on top. Rollers shape it to the target thickness (9.5mm, 12.5mm, 15mm, etc.).
4. Setting. The gypsum rehydrates and sets hard within minutes as it moves along the production line. The board is still wet but structurally stable.
5. Drying. The formed board passes through a long heated dryer to remove excess moisture. This takes 30-60 minutes depending on thickness.
6. Cutting. The continuous board is cut into standard sheet sizes (2.4m, 3m, etc.).
7. Stacking and wrapping. Sheets are bundled, wrapped, and shipped to merchants.

The whole process from raw gypsum to finished board takes about 90 minutes. A single production line can produce 30-50 million m² of board per year.

Gypsum board vs plasterboard vs drywall

These three terms describe the same product but come from different places.

Plasterboard (UK)

The most common term in the UK construction industry. Called plasterboard because the core is gypsum plaster. Builders, plasterers, and merchants all say plasterboard. You'll see it on price lists, delivery notes, and site conversations.

Gypsum board (technical/international)

The formal term used in British Standards (BS EN 520), technical datasheets, and academic papers. Also used internationally because gypsum is the chemical name. If you're reading a manufacturer's spec sheet or a Building Regulations document, it'll say gypsum board.

Drywall (US/Canada)

American and Canadian term. Called drywall because it replaced wet plaster application (lath and plaster). If you're reading US construction guides or watching American YouTube videos, they'll say drywall. The product is identical but American board sizes are different (4ft x 8ft is standard there vs 1200mm x 2400mm in the UK).

All three terms are correct. Use whichever fits your audience. Builders say plasterboard, engineers say gypsum board, Americans say drywall.

Types of gypsum board

Standard white gypsum board is the base product but there are many specialist versions with different additives or core compositions.

Standard board (white core)

General-purpose board for internal walls and ceilings in dry conditions. White or grey paper face. No special additives. Cheapest option. Suitable for living rooms, bedrooms, hallways.

Moisture-resistant board (green core)

Contains water-repellent additives and green paper facing. Used in bathrooms, kitchens, utility rooms. Not waterproof but resists short-term moisture exposure better than standard board. Must still be tiled or painted with moisture-resistant paint.

Fire-resistant board (pink core)

Contains glass fibre and vermiculite to improve fire resistance. Pink or red paper facing. Provides 30 minutes (12.5mm), 60 minutes (15mm), or 90 minutes (19mm) fire resistance. Required in escape routes, attached garages, party walls, and commercial buildings. Specified as Type F in British Standards.

Impact-resistant board

Reinforced core with higher density. Used in high-traffic areas like school corridors, hospital wards, public hallways. Resists dents and damage from trolleys, wheelchairs, and general impacts.

Acoustic board

Higher density core for better sound insulation. Often combined with fire resistance. Used in party walls, cinema rooms, recording studios. Provides 3-5dB better sound reduction than standard board of the same thickness.

Vapour control board (foil-backed)

Standard board with aluminium foil bonded to one face. Acts as a vapour barrier in timber frame walls or cold roofs. The foil side faces the warm side of the insulation to prevent condensation in the cavity.

Why is gypsum used instead of other materials?

Gypsum has a unique combination of properties that make it ideal for internal wall and ceiling lining.

Fire resistance

The 21% chemically-bound water is released as steam when heated, absorbing energy and slowing fire spread. No other common building material does this. Cement board is fire-resistant but much heavier and harder to cut. Timber burns. Gypsum gives you fire protection without the weight or cost of masonry.

Workability

Gypsum board cuts cleanly with a knife, screws hold well, and it's light enough for one person to handle (up to 12.5mm thickness). Compare that to blockwork or cement board, which need power tools and two people minimum.

Cost

Gypsum is cheap. Natural deposits are abundant and FGD gypsum from power stations is a waste product. Processing is energy-efficient. A 12.5mm x 2.4m sheet costs £7.50-8.50 retail. Equivalent area in blockwork costs £15-20 in materials alone plus far higher labour.

Sound insulation

Gypsum's density (around 680 kg/m³ for standard board) provides good airborne sound insulation. A single 12.5mm layer gives about 30dB reduction. Double that to 25mm and you hit 40dB, enough to meet Building Regulations for party walls.

Thermal mass

Gypsum has moderate thermal mass, helping to stabilise internal temperatures. Not as good as masonry but better than timber or insulation alone.

British Standards for gypsum board

Gypsum board sold in the UK must meet BS EN 520:2004+A1:2009, the European standard for gypsum plasterboard. This defines product types, performance requirements, testing methods, and marking.

The standard categorises boards by type:

• Type A: Standard board
• Type H: Moisture-resistant (controlled water absorption)
• Type F: Fire-resistant (enhanced fire performance)
• Type D: Low density (lighter boards for ceilings)
• Type E: Low water absorption (extreme moisture resistance)

Most residential work uses Type A for dry areas, Type H for bathrooms, and Type F where Building Regulations require fire resistance. Manufacturers print the type designation on the board edge or paper face.

Environmental considerations

Gypsum board is relatively low-impact compared to cement-based products. Production energy is lower because calcination happens at 150-180°C rather than 1400°C for cement. Around 40% of UK gypsum comes from recycled FGD sources.

End-of-life gypsum board can be recycled. British Gypsum operates a take-back scheme collecting offcuts and demolished board from sites. The gypsum is recalcined and fed back into production. Contamination with paint or plaster skim makes recycling harder but clean offcuts are 100% recyclable.

Landfilling gypsum is discouraged because it can generate hydrogen sulphide gas in anaerobic conditions. Most waste management sites now segregate gypsum for recycling rather than general landfill.

Related guides

• Complete guide to plasterboard types
• Plasterboard thickness guide
• Plasterboard sizes UK
• Soundproof plasterboard options