Fibre Reinforced Facade Encyclopedia: Materials
GFRC panels are factory made facade or feature units formed from a sprayed glass fibre reinforced concrete (GRC, GFRC) skin, typically 12 to 20 mm thick, stiffened either by ribs formed in the same pour or by fixing the skin to a light gauge steel stud frame through flexible anchors. The material is covered on the glass fibre reinforced concrete page; this page is about the panel as a delivered product, which is where the size limits, the anchor design, the joints and the tolerances are decided.
A GFRC panel is a thin skin doing two different jobs. It resists wind load between its fixings, and it has to survive demoulding, turning, transport and lifting, which frequently impose higher stresses than anything the panel ever sees in the wall.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Skin thickness | 12 to 20 mm sprayed | Measured as an average with a stated minimum |
| Weight in service | 30 to 50 kg/m² | Skin plus ribs or stud frame; ShapeShell-RC published range |
| Ribbed panel size, typical | up to about 3.0 by 6.0 m | Governed by handling stresses and transport, not by strength |
| Stud frame panel size, typical | up to about 3.6 by 7.2 m | Frame carries the load; skin carries only its own span |
| Rib spacing | 500 to 900 mm typical | Formed over a foam or timber former in the same spray operation |
| Rib or return depth | 50 to 100 mm typical | Sets the panel stiffness and the overall unit depth |
| Flex anchors | 3 to 6 mm stainless rod at 400 to 600 mm centres | Allow the skin to move relative to the frame |
| Joint width | 12 to 20 mm typical | Sized from panel length, movement and erection tolerance |
| Manufacturing tolerance | commonly ±3 mm on dimensions up to 3 m | Check the GRCA practice recommendation and the project specification |
| Fire | Cementitious, non-combustible where tested to AS 1530.1 | ShapeShell-RC: Not Deemed Combustible, Ignis Labs |
Two ways to build a panel
A ribbed single skin panel is sprayed in one operation. Formers, usually foam blocks or timber, are placed on the back of the wet skin and over-sprayed so the ribs become continuous with the face. The whole unit is one material, it moves as one, and it is the lightest and most direct construction. It suits panels up to roughly 3 by 6 metres and is the usual choice for moulded, curved and deeply modelled geometry.
A stud frame panel separates the two jobs. A light gauge galvanised steel frame carries the panel loads back to the building, and a flat or shallow skin is held off that frame by flexible anchors so it can shrink, expand and move independently. This construction reaches larger unit sizes, takes point loads and back fixings more easily, and is the normal answer for large flat rainscreen formats. It is also heavier, deeper and slower to make.
What limits panel size
Strength rarely limits a GFRC panel. Four other things do. The mould is first: a panel can be no larger than the tooling, and the cost of the mould is the largest single line in a low repetition order. Transport is second, because a wide or tall unit moves as an oversize load. Craneage is third, since a unit of 3 by 6 metres at 40 kg per square metre is roughly 720 kg before the frame and lifting frame are counted. Handling stress is fourth and is the one most often underestimated: demoulding, turning a panel from the flat to the vertical, and lifting from a stillage all put the thin skin into bending in directions it will never see in the wall.
For that reason the panel schedule is set with the fabricator early. Splitting an elevation into more and smaller units usually costs less than the special handling, permits and crane hours a few large ones demand, and it adds joints that absorb building movement.
Anchors and fixings
Stud frame panels use two anchor types working together. Gravity anchors carry the dead weight of the skin into the frame at a small number of designated points. Flex anchors, typically stainless steel rod bent to shape and encapsulated in a thickened bonding pad, restrain the skin against wind load but flex enough to let it move in plane. The rule they exist to satisfy is that the skin must never be restrained in two directions by two stiff connections, because the resulting shrinkage or thermal strain has nowhere to go except into a crack.
Fixing the panel back to the building is a separate design. Ribbed panels are usually supported on cast-in or bolted brackets bearing on the rib or an edge return, with top restraints that take wind load only and permit vertical movement. Larger formats use a hook-on rail arrangement so units can be hung and adjusted from the front. Every bracket needs an adjustment range in three axes to absorb structural tolerance, and the fixings, the sleeves and the packing shims should be stainless or equivalently durable because they are unreachable once the panel is up.
Joints, movement and weathering
GFRC moves. It has a thermal expansion coefficient in the range of 10 to 20 x 10⁻⁶ per °C and a moisture movement that is small but real, so joint widths are calculated from the panel length, the expected temperature range and the erection tolerance rather than taken from a standard detail. Joints below about 10 mm leave nothing for site adjustment and tend to be closed on one panel and open on the next.
Both joint strategies are used. A sealed joint with a backing rod and a movement capable sealant is simpler to build and depends entirely on the sealant, which has a shorter service life than the panel and must be reachable for replacement. An open drained joint over a ventilated cavity keeps water off the sealant line altogether and is the normal choice for rainscreen construction, with the drainage, flashing and cavity barrier design carrying the waterproofing instead. Either way the cavity behind the panels is part of the external wall for fire purposes and needs cavity barriers detailed with the panel layout, not after it.
Tolerances, handling and installation
Manufacturing tolerances follow the GRCA practice recommendation and the project specification, commonly around ±3 mm on dimensions up to 3 metres with separate limits on squareness, bow and twist, and a stated minimum rather than nominal skin thickness. They are meaningless unless the structural tolerance behind is also specified: a concrete frame built to ±25 mm needs brackets with that much adjustment, and the joint width has to cover the remainder.
Panels are not demoulded or handled before the mix has developed the strength to take it, typically after 16 to 24 hours, and moist curing follows unless the mix is polymer modified. Units travel vertically in stillages, not flat, lifting points are the ones on the shop drawings, and panels are packed and shimmed at the designated bearing points only. Batch test boards for modulus of rupture and limit of proportionality accompany production and are the evidence that delivered panels match the design values.
Fire and compliance
GFRC has no polymer matrix, so a tested product can be classified as non-combustible and used on the external wall of a Type A or Type B building under the Deemed-to-Satisfy provisions of NCC 2022 Volume One (check the edition adopted in your jurisdiction). ShapeShell-RC holds an AS/NZS 1530.1 result of Not Deemed Combustible from Ignis Labs. The classification belongs to the tested product and thickness, not to GFRC as a category.
The panel is not the whole wall. Steel frames, insulation, membranes, sealants and any foam rib formers left in place are separate products with their own provisions, and the external wall is assessed as a system. A panel with a valid AS 1530.1 report can still sit in a non-compliant wall if what is behind it was never checked.
Standards and references
- GRCA Specification for the Manufacture, Curing and Testing of GRC Products, and the GRCA Practical Design Guide
- BS EN 1169 (factory production control) and BS EN 1170 parts 1 to 8 (GRC test methods)
- PCI MNL-128 Recommended Practice for Glass Fiber Reinforced Concrete Panels
- AS 1530.1 (combustibility); NCC 2022 Volume One C2D10 and Specification 7
- AS/NZS 1170.2 (wind actions) and AS 4284 (building facade testing)
- AS 3566 and AS 4312 or equivalent for fixing durability in the relevant exposure category
Where this matters on a ShapeShift project
One Sydney Harbour, Barangaroo: A high rise residential tower, and a good example of what a moulded panel schedule has to reconcile: a repeating three-dimensional profile on the face, and the structural tolerance of the frame behind it.
Related terms
Questions specifiers ask
How big can a GFRC panel be?
Typically up to about 3 by 6 metres for a ribbed single skin panel and about 3.6 by 7.2 metres on a steel stud frame. The limit is set by the mould, transport, crane capacity and handling stresses rather than by the strength of the material.
What is the difference between a ribbed panel and a stud frame panel?
A ribbed panel is stiffened by ribs sprayed as part of the same skin and moves as one element. A stud frame panel hangs a thinner skin off a light gauge steel frame through flexible anchors, so the skin can move independently. Ribbed suits moulded geometry; stud frame suits large flat formats.
What are flex anchors for?
They restrain the GFRC skin against wind load while allowing it to move in plane relative to its steel frame as it shrinks and expands. Without that freedom, thermal and moisture strain is resisted by the connection and the skin cracks.
How wide should the joints be?
Calculate from panel length, temperature range, moisture movement and erection tolerance. Twelve to 20 mm covers most facade panels. Anything under about 10 mm leaves no room for site adjustment.
Are GFRC panels non-combustible?
A tested product can be. ShapeShell-RC holds an AS/NZS 1530.1 result of Not Deemed Combustible from Ignis Labs. The result applies to the tested product and thickness, and the frame, insulation and membranes behind the panel are assessed separately.
How much do GFRC panels weigh?
Between 30 and 50 kg per square metre including ribs or frame, which is roughly a tenth of a 150 mm precast panel and light enough to reclad a building whose structure cannot take precast.
Working out panel sizes, anchors and joints for a GRC facade? ShapeShell-RC panels are produced from CNC-cut moulds and batch tested for modulus of rupture and limit of proportionality to the GRCA specification. See ShapeShell-RC specifications
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.