GRC / GFRC Panels: Glass Fibre Reinforced Concrete Facades

Glass fibre reinforced concrete, known as GRC in Britain and Asia and GFRC in North America, is a thin cement-based composite reinforced with alkali-resistant glass fibres. It lets designers produce facade panels, screens, column casings and decorative elements that look like concrete or stone but are a fraction of the thickness and weight of conventional precast.

This article explains what GRC is, how it is manufactured, how panels are fixed to a building, where it performs well and where it does not, and what an engineer checks before approving a GRC package. It sits within our wider guide to fibre-reinforced concrete, which covers steel and synthetic fibres as well.

What glass fibre reinforced concrete is

GRC is a mortar rather than a coarse-aggregate concrete: typically cement, fine sand, water, admixtures, often a polymer, and glass fibres. The fibres are distributed through the matrix and carry tension, so the material can be used in sections as thin as 10 mm to 15 mm while still resisting handling, wind and impact loads. A conventional precast panel doing the same job might need to be several times thicker with steel mesh and cover.

The fibres must be alkali-resistant (AR) glass. Ordinary glass is attacked by the high alkalinity of cement paste and loses strength over time. The breakthrough came from research at the UK’s Building Research Establishment in the 1960s, which found that glass with a high zirconia content resisted that attack; the formulation was then commercialised by Pilkington around the start of the 1970s, launching the GRC industry. Zirconia-bearing AR glass remains the standard today.

How GRC panels are made

There are two main manufacturing methods, and they produce materials with different properties.

Spray-up: a concentric spray gun chops continuous AR glass roving and sprays it simultaneously with the mortar into a mould, building up the panel in layers and compacting each by roller. It gives a high fibre content, typically around 5% by weight, and the best mechanical properties. Most architectural facade panels are sprayed.
Premix: short chopped fibres are mixed into the mortar, which is then cast, vibrated or sprayed into moulds. Fibre content is lower, typically around 2% to 3%, so strength is lower, but it suits smaller, intricate units and high-volume products.

Many panels start with a thin face coat without fibres, sprayed first into the mould to give a dense, fine finish, followed by the fibre-reinforced backing. After demoulding, panels are cured under controlled conditions. Moulds can be fibreglass, timber, silicone or steel, which is what makes complex shapes economical when they repeat.

Panel types and fixing systems

A thin GRC skin on its own is flexible, so large panels need stiffening. The common arrangements are:

Single skin with ribs: the GRC is thickened locally into integral ribs. Suitable for smaller panels.
Stud-frame panels: a light galvanised or stainless steel frame is attached to the back of the GRC skin with flexible steel anchors bonded in GRC pads. This is the standard approach for large facade panels.
Sandwich panels: two GRC skins with an insulating core, used less often today.

The stud-frame arrangement deserves a note. The GRC skin and the steel frame move differently with temperature and moisture, so the anchors are designed to flex rather than restrain. If anchors are too stiff, or too many are rigidly fixed, the skin cracks as it shrinks and expands. The frame is then fixed back to the building structure with bearing connections that carry weight and restraint connections that resist wind, with slotted holes to absorb tolerances and movement.

Where GRC works well

GRC is at its best where shape and weight matter more than raw strength:

Facade panels with deep profiles, returns, curves or texture that would be heavy or impractical in precast.
Perforated screens and patterned shading elements, popular in tropical architecture.
Column and beam casings, cornices, balustrades and heritage replicas.
Refurbishment, where a light facade avoids strengthening the existing structure.

It is non-combustible in its basic form, weathers like concrete, and can take a range of finishes, from smooth to acid-etched, sandblasted or pigmented through the body. Compared with the options set out in our guide to types of cladding, it occupies a space between precast concrete and lightweight boards.

Limitations and long-term behaviour

GRC is not structural concrete. It should not be used to carry building loads, and its strength in tension and bending is not permanent. As the material ages, the composite becomes more brittle; its long-term bending strength and strain capacity are lower than the values measured at 28 days. Good design uses long-term properties, not early-age test results, and keeps working stresses well below them.

Other points to watch:

Shrinkage and crazing: GRC is cement-rich, so drying shrinkage is higher than in normal concrete. Fine surface crazing can occur, especially with poor curing.
Anchor corrosion: embedded steel and anchors must be stainless or adequately protected, since the skin offers little cover.
Quality control: properties depend heavily on the operator in spray-up. Daily test boards, fibre content checks and bending tests are essential.
Handling damage: thin edges chip if panels are lifted or stored carelessly.

European standard EN 1169 covers factory production control for GRC, and test methods for fibre content and bending strength are set out in the EN 1170 series. Industry guidance from the GRC trade association is widely used for design and specification.

What to check before approving a GRC package

When reviewing GRC for a project, the structural engineer and facade consultant typically look at the panel design calculations (using long-term properties), the anchor and stud-frame design, the connections to the primary structure and their capacity in the slab or beam edges, and the manufacturer’s quality regime. Wind load, self-weight, thermal movement and seismic or drift requirements all feed into the fixing design.

The connections into the building are where problems most often appear on site: brackets that clash with reinforcement or post-tensioning tendons, insufficient edge distance for anchors, or tolerances that the brackets cannot absorb. Many GRC elements are delivered as part of a wider precast or facade package, so coordination between trades is essential. For existing GRC on older buildings, cracking, delamination around anchors and corroded fixings are the typical findings in a facade inspection.

Frequently asked questions

Is GRC the same as GFRC?

Yes. GRC (glassfibre reinforced concrete) is the term used in Britain, Europe and much of Asia, while GFRC (glass fiber reinforced concrete) is the North American term. Both describe the same material: a cement mortar reinforced with alkali-resistant glass fibres.

How thick are glass fibre reinforced concrete panels?

Typical sprayed GRC facade skins are around 10 mm to 15 mm thick, stiffened by ribs or a steel stud frame for larger panels. This is far thinner than conventional precast concrete cladding, which is why GRC is so much lighter.

Is GRC fire-resistant?

GRC is a cement-based material and is non-combustible in its basic form, making it a good choice for facades from a fire perspective. Any polymer additives, sealants, insulation or backing materials in the system should still be checked against the Fire Code.

Can GRC be used structurally?

No. GRC is designed to carry its own weight, wind load and handling stresses only. Its long-term strength is lower than its early-age strength, so it should never be used to support floors, beams or other building loads.

Why do GRC panels crack?

Common causes are restrained shrinkage and thermal movement from overly stiff anchors or fixings, poor curing, low fibre content from inconsistent spraying, handling damage and corrosion of embedded steel. Most of these are prevented through careful anchor design and factory quality control.

Reviewing a GRC facade package or assessing cracked panels on an existing building? Talk to our consultancy or get in touch.