Walk into almost any modern office, hospital, or apartment interior and you will see it: smooth walls and ceilings that went up in days, not weeks. That speed comes from gypsum board — also called drywall, plasterboard, or wallboard. It is one of the most widely used interior building materials in the world, and it deserves a proper technical look.
What Is Gypsum Board?
Gypsum board is a factory-made panel consisting of a gypsum plaster core sandwiched between two sheets of heavy paper (the facers). The core gives the board its fire resistance and rigidity; the paper facers give it a smooth finish surface and most of its tensile strength. Because it is installed dry — screwed to a metal or timber frame and jointed — it is also called drywall construction, as opposed to wet plaster work.
Composition of Gypsum Board
The core of the board is made from calcium sulfate dihydrate (CaSO₄·2H₂O) — the mineral gypsum. The chemistry is worth knowing because it explains the fire performance:
- Raw gypsum rock is calcined (heated) to drive off part of its water, producing calcium sulfate hemihydrate — plaster of Paris.
- In the board plant, this plaster is mixed with water, additives (starch, foamers, retarders, and sometimes glass fibre), and poured between two continuous paper sheets.
- The slurry rehydrates and sets back into the dihydrate form, bonding to the paper as it hardens.
The chemically bound water in the gypsum core is the board’s built-in fire protection: when heated, the water is released as steam, which slows the temperature rise on the unexposed face. That is why even a standard board offers meaningful fire resistance, and why fire-rated variants exist.
How Gypsum Board Is Made (Brief Overview)
- Calcining — mined or synthetic gypsum is heated to produce plaster powder.
- Mixing — plaster, water, and additives are blended into a slurry.
- Forming — the slurry is spread onto the bottom paper sheet; the top sheet is folded over the edges.
- Setting and cutting — the continuous ribbon sets, is cut to length, and then dried in kilns to remove free water.
- Finishing — boards are trimmed, bundled, and shipped. Long edges are usually tapered so joints can be filled flush.
Types of Gypsum Board
Not all boards are the same. The type is normally identified by the colour of the paper facing:
| Type | Facing colour | What is different | Typical use |
|---|---|---|---|
| Regular (standard) board | Ivory/white | Plain gypsum core | General walls and ceilings in dry areas |
| Moisture-resistant board (“green board”) | Green | Water-repellent additives in core and treated paper | Bathrooms, kitchens, laundries (humid, not wet, areas) |
| Fire-resistant board (Type X) | Pink/red | Glass fibre and other additives in the core for higher fire ratings | Fire-rated partitions, shafts, garages |
| Abuse/impact-resistant board | Varies | Denser core, sometimes fibre-reinforced | Corridors, schools, hospitals — areas with hard use |
| Exterior sheathing board | Varies (often glass-mat) | Fibreglass mat facers instead of paper | Behind cladding on exterior walls |
| Foil-backed board | Aluminium foil on back face | Vapour-retarder foil laminated to the board | Walls where a vapour barrier is needed |
Practical note: “moisture-resistant” does not mean waterproof. Green board handles humidity and occasional splashes; it should never be used inside shower enclosures or other continuously wet zones — tile backer boards or cement boards belong there.
Standard Sizes and Thicknesses
Gypsum boards are sold in metric and imperial sheet sizes. The common standards, as of 2026, are:
- Sheet sizes: 1200 × 2400 mm is the standard metric sheet; 1220 × 2440 mm (4 ft × 8 ft) is the imperial equivalent. Longer sheets (up to 3000–3600 mm) are available for full-height walls.
- Thicknesses: 9.5 mm and 12.5 mm are the everyday choices; 15 mm (and heavier) boards are used where better fire rating, sound insulation, or impact resistance is needed. Thinner 6–9 mm boards exist for curved work and overlays.
- Edges: long edges are tapered for jointing; short ends are square-cut.
For reference, gypsum board is light — roughly 800–960 kg/m³, or about one-fifth the weight of an equivalent masonry wall — which is why partitions can sit on slabs without heavy structural provision.
Applications in Buildings
- Interior partitions — stud-framed drywall partitions divide floor plates quickly and can be reconfigured later.
- False ceilings — gypsum boards on a suspended metal grid give level ceilings that hide services (ducts, wiring, pipes) with access where needed.
- Wall lining — boards fixed to masonry or concrete walls give a smooth, paint-ready surface (dry lining) without wet plaster.
- Fire-rated separations — multi-layer Type X systems form rated walls and ceiling membranes around shafts, corridors, and between occupancies.
- Acoustic partitions — double-layer boards on staggered studs with insulation are a standard way to meet sound-rating requirements between rooms.
For how partitions fit into the bigger picture of wall systems, see the guide on wall classification and types.
Advantages of Gypsum Board
- Speed — dry installation is far faster than blockwork plus plaster.
- Fire resistance — the gypsum core’s bound water gives inherent fire protection, upgraded further in Type X boards.
- Lightweight — low dead load on the structure; easy handling on site.
- Smooth finish — paint-ready surface with minimal skilled labour.
- Flexibility — partitions can be dismantled and reconfigured; services run easily inside the cavity.
- Cost — generally cheaper per square metre than masonry partitions with plaster.
Limitations — Where Gypsum Board Should Not Be Used
- Wet areas: standard boards fail in continuous dampness — the core softens and paper feeds mould. Use moisture-resistant board only for humid (not wet) zones.
- Structural use: gypsum board is non-load-bearing; it never replaces masonry or concrete walls structurally.
- Impact damage: standard boards dent and puncture easily — corridors and public areas need abuse-resistant types or protective dado rails.
- Fixing heavy loads: shelves, cabinets, and sanitary ware need proper anchors into studs or backing, not just the board face.
- Exterior exposure: paper-faced board must never be left exposed to weather; exterior use needs glass-mat sheathing types behind cladding.
Frequently Asked Questions
What is gypsum board made of?
A core of set gypsum plaster (calcium sulfate dihydrate) between two heavy paper facers. Fire-rated types add glass fibre to the core.
What is the standard size of a gypsum board?
1200 × 2400 mm (metric) or 1220 × 2440 mm (4 × 8 ft). Common thicknesses are 9.5 mm, 12.5 mm, and 15 mm.
Can gypsum board be used in bathrooms?
Moisture-resistant (green) board is acceptable for humid bathroom areas, but not inside showers or other continuously wet zones — use cement backer board there.
What is the difference between Type X and regular gypsum board?
Type X has glass fibre and other additives in the core, giving it a tested fire-resistance rating (typically 1 hour for a 15.9 mm / ⅝ in. board in standard assemblies). Regular board has no rated assembly.
Is drywall load-bearing?
No. Gypsum board partitions are non-structural and must never be relied on to carry building loads.
Final Thoughts
Gypsum board earns its place through speed, fire performance, and economy — but only when the right type is matched to the right location. Specify the board for the exposure it will actually see, respect its limits in wet and high-impact areas, and it will give decades of trouble-free service.
Written by Mohsin Raza Adil — BSc Civil Engineering Technologist (NTC-registered), Pakistan.
Mohsin Raza Adil
BSc Civil Engineering Technologist (NTC-registered), Pakistan. I write practical, field-tested guides on construction materials, soil testing and site engineering — the way it is actually done on site.
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