GRC façade panels: design, fixing systems and cost factors

Why architects choose GRC for façades

• Form: curves, deep relief, fins, jali and three-dimensional shapes that would be too heavy or costly in stone or precast concrete.
• Weight: thin sections mean less load on the frame and smaller fixings.
• Durability: no steel reinforcement to rust; mineral surface that weathers like stone.
• Fire: non-combustible, an important point after façade fires involving combustible cladding.
• Consistency: factory-made, so repeated panels match.

The three main panel systems

System	How it works	Typical use
Direct-fixed (self-supporting)	Solid or ribbed panels, typically 20–40 mm, with cast-in sockets or edge returns, bolted to the RCC frame with stainless-steel brackets	Jali, fins, window surrounds, small and medium cladding panels, low- and mid-rise buildings
Stud-frame	A thin sprayed GRC skin (about 10–15 mm) connected to a galvanised steel stud frame by flexible “flex anchors”; the frame carries gravity and wind loads to the structure	Large storey-height panels, high-rise façades, complex shapes
Sub-frame / rail	Panels hung on a secondary steel or aluminium grid fixed to the wall	Over masonry infill, uneven walls, refurbishment

The stud-frame system is the basis of the US PCI 128 specification. In Indian residential and mid-rise work, direct-fixed panels and jali are far more common.

Thickness and weight

GRC weighs about 2,000 kg/m³, so the weight depends almost entirely on thickness:

Element	Thickness	Approx. weight
Stud-frame skin	10–15 mm	20–30 kg/m² plus the frame
Direct-fixed flat panel	20–30 mm	40–60 kg/m² (less with ribbed backs)
Façade jali	30–35 mm	60–70 kg/m² solid, much less after openings

For comparison, 150 mm precast concrete cladding weighs around 360 kg/m², and 40 mm stone with its fixings well over 100 kg/m².

Design points to get right early

• Panel size: limited by transport, lifting, and the moulds. Agree a panel layout with joints that line up with the architecture.
• Fixing positions: decide which slab edges, beams or columns take each panel before the structure is cast; retro-fitting anchors is slower and costlier.
• Movement: GRC expands and shrinks with moisture and temperature. Each panel needs one fixed point and sliding or flexible connections elsewhere, never rigid restraint on all sides.
• Tolerances: RCC frames are rarely perfectly true. Brackets need slotted holes or shims for adjustment.
• Drips and edges: include drip grooves and avoid flat tops that collect dirt and water.
• Finish sample: approve colour and texture on a full-size sample in daylight.

Joints and waterproofing

A GRC façade usually keeps water out in one of two ways:

• Sealed joints: 10–20 mm joints with a backer rod and a flexible sealant (often polyurethane or silicone) designed for the expected movement. Sealant needs inspection and periodic replacement over the building’s life.
• Rainscreen: open or baffled joints with a drained, ventilated cavity behind the panels and a waterproof wall behind that. It’s more forgiving but needs the backing wall to be weather-tight.

Installation sequence

1. Survey the structure and set out panel grid lines.
2. Fix brackets or sub-frame to the structure and check them against levels.
3. Lift panels in sequence, usually bottom up, and bolt them to the brackets.
4. Align, shim and tighten. Make sure sliding connections are left free.
5. Seal joints, clean down, and touch up or apply the final coating.

What drives GRC façade cost

• Number of different panel types: fewer unique moulds means lower cost per m².
• Shape complexity: deep relief, double curves and returns cost more to mould and cast.
• System: stud-frame panels add steel and engineering; direct-fixed panels add brackets.
• Finish: grey, white, pigmented, acid-etched or painted.
• Height and access: cranes, scaffold or rope access.
• Quantity: larger areas spread fixed costs.

Use the 10 GRC cladding ideas for design inspiration and the GRC technical data sheet for material values.

Common mistakes

• Fixing panels with mortar or tile adhesive instead of mechanical anchors.
• Rigidly restraining large panels, which leads to cracking.
• Using mild steel fixings without corrosion protection; use stainless steel or properly galvanised steel.
• Choosing panel sizes before checking site lifting and access.
• Comparing quotes without comparing thickness, fibre and system.

Frequently asked questions