Fibre Reinforced Facade Encyclopedia: Materials
Glass fibre reinforced concrete is a composite of Portland cement, fine silica sand, water, admixtures and alkali resistant glass fibre, sprayed or cast into panels 10 to 20 mm thick. It is called GRC in Australia, the UK and most of Asia, and GFRC in North America; the material is the same. The glass fibre carries tension the way steel does in conventional concrete, so a GRC skin can be a tenth the thickness and a fifth the weight of a precast panel doing the same job.
A 15 mm sprayed GRC facade skin with integral ribs weighs about 30 to 50 kg per square metre. The equivalent 150 mm precast panel weighs about 360 kg per square metre.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Density | 1,900 to 2,100 kg/m³ | Sprayed GRC at 28 days |
| Panel thickness | 10 to 20 mm skin | Ribs or a stud frame add stiffness |
| Weight in service | 30 to 50 kg/m² | Skin plus ribs or frame; ShapeShell-RC published range |
| Modulus of rupture (MOR) | 20 to 30 MPa sprayed, 10 to 14 MPa premix | Peak flexural stress at 28 days |
| Limit of proportionality (LOP) | 7 to 11 MPa | First crack; used for serviceability design |
| Fibre content | 5% by weight sprayed, 3 to 3.5% premix | Alkali resistant glass, 16% or more zirconia |
| Thermal expansion | 10 to 20 x 10⁻⁶ per °C | Similar to concrete |
| Thermal conductivity | about 0.4 W/m·K | ShapeShell-RC published value 0.39 |
| Fire | Non-combustible where tested to AS 1530.1 | ShapeShell-RC: Not Deemed Combustible, Ignis Labs |
| Service life | 40 to 50 years | Depends on mix, cure and exposure |
How GRC differs from concrete
Conventional reinforced concrete needs at least 25 to 50 mm of cover over steel bars to stop corrosion, which is why precast panels are rarely thinner than 100 mm. GRC has no steel in the skin. The reinforcement is millions of short glass filaments distributed through the cement, so cover is irrelevant and the panel can be as thin as the mould and the design loads allow.
The trade-off is that GRC is a thin-section material. It carries wind load and its own weight well but is not used as a load-bearing structural element. Large panels are stiffened with ribs formed in the same pour, or fixed to a light steel stud frame through flexible anchors that let the skin move independently of the frame.
How it is made
Two processes dominate. In sprayed GRC, a spray gun delivers cement slurry and chopped glass roving at the same time, building the skin up in layers that are roller compacted against the mould. Sprayed GRC reaches the highest fibre content and the highest strength, and is the process for facade panels. In premix GRC, short fibres are mixed into the slurry and the material is cast or sprayed as a homogeneous mix; it suits smaller and more complex elements at lower strength.
After demoulding at 16 to 24 hours, GRC is moist cured for about seven days unless the mix is polymer modified, in which case an acrylic admixture allows air curing. The mould is where the finish is decided: smooth off-form, textured, exposed aggregate, acid etched or sandblasted surfaces all come from the mould face and the mix, not from a coating.
Where it is used
- External facade panels, particularly curved, folded or deeply profiled forms that precast cannot cast thin enough to lift
- Recladding, where the existing structure cannot carry the weight of precast or masonry
- Sunshades, fins, soffits, column casings and parapets
- Planters, seating and street furniture
- Stay-in-place formwork for civil structures such as bridge parapets and tunnel portals
GRC is chosen when the geometry is complex, the structure is weight-limited, or the external wall must be non-combustible and the designer still wants a moulded rather than flat panel.
Fire performance
GRC is a cementitious material with no polymer matrix, so it can be tested and classified as non-combustible. Under the National Construction Code, external walls of Type A and Type B buildings must be non-combustible, and a GRC product with an AS 1530.1 result of Not Deemed Combustible satisfies the Deemed-to-Satisfy route directly. Internationally the equivalent tests are EN ISO 1182 for Class A1 or A2 under EN 13501-1, and ASTM E136 under the International Building Code.
Durability
Early GRC made with ordinary E glass lost strength as the alkaline cement attacked the fibre. Alkali resistant glass with 16 percent or more zirconia, introduced in the 1970s and now specified by the GRCA, largely solved this, and modern mixes with low alkali cements, pozzolans and polymer additions retain a high proportion of their strength over decades. Design still uses long-term aged property values rather than 28-day figures. GRC does not corrode, does not rot, resists freeze-thaw with a low water absorption mix, and takes UV without a coating.
Standards and references
- GRCA Specification for the Manufacture, Curing and Testing of GRC Products
- BS EN 1169 (factory production control) and BS EN 1170 parts 1 to 8 (test methods for GRC)
- ASTM C1228, C1229 and C1230 (GRC test methods, US)
- PCI MNL-128 Recommended Practice for Glass Fiber Reinforced Concrete Panels
- AS 1530.1 (combustibility), NCC 2022 Volume One C2D10 and C1V3 (check the edition adopted in your jurisdiction)
- EN ISO 1182 and EN 13501-1; ASTM E136 and IBC Chapter 14
Where this matters on a ShapeShift project
One Sydney Harbour, Barangaroo: A high rise residential tower, and the case that shows why this material exists. The external walls fall under the non-combustible provisions, and the architecture calls for a moulded, three-dimensional panel rather than flat sheet.
Related terms
Questions specifiers ask
Is GRC the same as GFRC?
Yes. GRC (glass reinforced concrete) is the term used in Australia, the UK, the Middle East and most of Asia. GFRC (glass fiber reinforced concrete) is the US term. The material, the standards and the manufacturing processes are the same.
Is GRC non-combustible?
GRC can be. It is a cementitious material with no polymer matrix, so a specific product can be tested to AS 1530.1, EN ISO 1182 or ASTM E136 and classified as non-combustible. ShapeShell-RC holds an AS/NZS 1530.1 result of Not Deemed Combustible from Ignis Labs. Check the report for the exact product and thickness you are specifying.
How thick is a GRC panel?
The skin is usually 10 to 20 mm. Panels are stiffened with integral ribs or fixed to a steel stud frame, so the overall depth of a facade unit is typically 100 to 200 mm even though the concrete itself is thin.
How much does GRC weigh?
About 30 to 50 kg per square metre for a facade panel including ribs or frame, compared with roughly 250 to 500 kg per square metre for precast concrete of 100 to 200 mm.
What is the difference between sprayed and premix GRC?
Sprayed GRC deposits slurry and chopped fibre together, reaching about 5 percent fibre and 20 to 30 MPa MOR; it is the process for facade panels. Premix mixes shorter fibres into the slurry first, reaching about 3 percent fibre and 10 to 14 MPa MOR; it suits smaller and intricate elements.
How long does GRC last?
Modern GRC made with alkali resistant glass and a controlled mix is designed for a 40 to 50 year service life. Design values use long-term aged strength, not 28-day strength, to allow for the gradual change in fibre and matrix properties.
Specifying GRC on a facade? ShapeShell-RC is our GRC system, non-combustible to AS 1530.1 and produced as complex geometry from CNC-cut moulds. See ShapeShell-RC specifications
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.