Fibre Reinforced Facade Encyclopedia: Materials
GFRG panels are interior wall, ceiling, column and feature elements cast from alpha gypsum plaster reinforced with chopped glass fibre, moulded as a thin shell and delivered paint ready. The material is called GRG in Australia and the UK and GFRG in North America. Because the panel takes its shape from a mould rather than from a sheet, GFRG is the standard way of building curved, coffered, perforated and sculptural interior surfaces that plasterboard cannot form.
A GFRG shell is cast 3 to 6 mm thick and weighs about 23 kilograms per square metre in service. The same geometry built up in plasterboard, framing and hand applied plaster would be several times that, and would take weeks longer on site.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Shell thickness | 3 to 6 mm | ShapeShell-RG cast range |
| Weight in service | about 23 kg/m² | ShapeShell-RG published figure |
| Binder | Alpha gypsum (alpha hemihydrate) | Denser and stronger than beta plaster |
| Reinforcement | Chopped E glass fibre | Typically about 5% by weight |
| Exposure | Interior, dry conditions only | Not for external or wet area use |
| Surface | Paint ready from the mould | No skim coat required on the face |
| Joint treatment | 50 to 100 mm butter joint, plaster and scrim | Finished flush and sanded on site |
| Element size | Limited by handling and transport | |
| Fire |
What GFRG panels are used for
- Curved and domed ceilings, vaults, coffers and bulkheads
- Column casings, column heads, capitals and pilasters
- Cornices, mouldings, light coves and reveal linings
- Perforated acoustic ceiling and wall panels over an absorber
- Feature walls with repeated three-dimensional relief
- Restoration and replication of existing plaster profiles
The argument for GFRG on a project is repeatability. Once the mould exists, every element is identical, dimensionally accurate and produced under factory conditions, which removes the variability of hand run plaster and moves a large amount of wet trade work off the critical path. The corresponding constraint is that changes after the mould is cut are expensive, so setting out and shop drawings have to be resolved earlier than for a sheet lining.
How they are made and fixed
Alpha gypsum slurry and chopped glass fibre are applied to the mould face in layers, either sprayed or laid by hand, and compacted to form a continuous shell. Timber, steel or additional plaster ribs are bonded into the back where a panel needs stiffness, and fixing plates or embedded inserts are cast in at the positions shown on the shop drawings. Demoulding follows within a few hours, since gypsum sets quickly, and panels are then dried before delivery.
On site, panels are screwed or bonded to a steel or timber back frame, or suspended from a ceiling grid using the cast-in fixing points. The back frame is the real dimensional control: gypsum panels are accurate, and any setting out error in the frame shows immediately at the joint line. Services, lighting and sprinkler penetrations should be located on the shop drawings so the openings are cast or cut in the factory.
Jointing and finishing
Adjacent panels are set with a gap of a few millimetres, which is filled with a gypsum butter joint reinforced with scrim over a width of 50 to 100 millimetres, then sanded flush. Done correctly the joint disappears completely, which is the reason GFRG is chosen for continuous curved surfaces where a plasterboard joint would telegraph.
The moulded face is paint ready and normally needs only sealing and finish coats. Because gypsum is porous, a sealer or primer is required before paint to even out suction, and the same applies at every jointed area where fresh plaster has been applied. Dark and high gloss paints will reveal any imperfection in the substrate, so the mock-up should be finished in the actual specified system.
Limits
Gypsum is soluble and rehydrates. GFRG is an interior material for dry conditions and must not be used externally, in wet areas, or anywhere subject to condensation or repeated high humidity. Where a project needs the same moulded geometry outside or in a wet environment, the cementitious or polymer systems are the alternatives: glass fibre reinforced concrete for a non-combustible external skin, fibre reinforced polymer where weight or span governs.
Impact resistance is moderate. A 3 to 6 mm shell at low level in a circulation route will be damaged, and either a thicker section, a local backing or a different material should be used below handrail height. Repairs, however, are straightforward: gypsum patches, sands and repaints invisibly, which is a genuine advantage over composite panels.
Specifying GFRG
State the shell thickness, the binder as alpha gypsum, the reinforcement, the back frame and fixing method, the joint treatment, the surface finish standard and the acceptance criteria for flatness and joint visibility. Require shop drawings showing every panel, its fixing points, its joint lines and its service penetrations, and require a mock-up of a representative panel and joint finished in the specified paint system.
Coordinate the ceiling or wall zone early. A moulded panel with a back frame needs more depth than a plasterboard lining, and the services above it have to be set out before the mould is cut. The installation and shop drawings entries cover the process; the GFRG entry covers the material in more detail.
Standards and references
- AS 2588 Gypsum plasterboard, and AS/NZS 2589 Gypsum linings: application and finishing, for finish levels and jointing practice
- ASTM C1355 Standard Specification for Glass Fiber Reinforced Gypsum Composites
- ASTM C472 Standard Test Methods for Physical Testing of Gypsum, Gypsum Plasters and Gypsum Concrete
- AWCI Technical Manual 12-B, Glass Fiber Reinforced Gypsum Fabrication and Installation
- AS 1530.3 early fire hazard properties, where a classification is required
Related terms
Questions specifiers ask
What is the difference between GFRG and plasterboard?
Plasterboard is a flat sheet product made in a continuous line and cut on site. GFRG is cast to shape in a mould, so it produces curved, coffered and sculptural forms as single accurate elements with concealed joints.
Can GFRG panels be used outside?
No. Gypsum is soluble and rehydrates in moisture, so GFRG is an interior material for dry conditions. For the same geometry externally, use glass fibre reinforced concrete or fibre reinforced polymer.
How much do GFRG panels weigh?
About 23 kilograms per square metre in service for a 3 to 6 mm cast shell, which is the ShapeShell-RG published figure. Ribs and back framing add to that.
Are GFRG panels non-combustible?
No claim should be made without a test. Gypsum performs well in fire because of its chemically bound water, but the classification belongs to the tested product and must name the standard and the testing body.
How are the joints between GFRG panels hidden?
With a gypsum butter joint reinforced with scrim across 50 to 100 millimetres, sanded flush and sealed before painting. Done properly the joint is not visible, which is why GFRG suits continuous curved surfaces.
Planning a moulded interior ceiling, column or feature wall? ShapeShell-RG is our glass fibre reinforced gypsum system, cast as a 3 to 6 mm paint ready shell. See ShapeShell-RG specifications
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.