GRC Component Decomposition Principles: Panel Splitting Logic and Per-Piece Weight Limits

How a curved architectural surface is decomposed into individual GRC panels is a design decision that sets the project's mould count, joint pattern, installation sequence, and visual outcome. Done well, the joints disappear into the design and the installation flows without surprises. Done poorly, the joints become the dominant visual feature and the site runs into collision after collision. This article walks through the five decomposition principles that govern good GRC panel splitting, with the per-piece weight limits that drive the rest of the decisions.

Why Decomposition Matters

For a 600 m² flowing wall, the architect's intent is one continuous surface. The GRC factory needs 80–150 individual panels, each with its own mould, its own handling protocol, its own installation step. The decomposition is the bridge between the two. It controls:

• Visual joint pattern (where the eye sees the seams)
• Mould count (more panels = more moulds = higher mould amortisation)
• Transport feasibility (each panel must fit on a truck)
• Hoisting feasibility (each panel must be liftable by the available crane)
• Installation sequence (each panel must be reachable without collision)
• Tolerance stack-up (more panels = more joints = more cumulative error)

Five principles guide a good decomposition. They sometimes pull against each other; the deepening designer's job is to balance them.

Principle 1: Hide Joints in the Design's Weak Spots

The best joint location is where the eye already expects a transition: a curve inflection point, a material change, a feature line in the design. A joint on a flat, smooth surface is the most visible; a joint at a curve transition is the least.

Application: for a flowing wall with multiple curvature changes, place joints at each inflection. The decomposition looks for curvature-discontinuity points in the NURBS model and aligns panel edges to those points.

Principle 2: Modularise Where Possible

If the design has repeating geometry (a façade with 30 identical balcony units, for example), the panel pattern should be modular — the same mould used 30 times rather than 30 unique moulds. Modular decomposition cuts mould cost dramatically (50%–80%) and reduces mould changeover time.

Application: identify repeating units in the design before splitting. The decomposition should preserve the repeat unit's geometry as a single panel, and only split within the unit when the unit is too large for mould fabrication.

Principle 3: Avoid Curvature-Discontinuity Within a Panel

A panel that contains a sharp curvature change (e.g., a corner where the surface goes from flat to curved) is harder to mould, harder to demould, and harder to install accurately than a panel on a single curvature. The mould must capture the discontinuity; the demoulding draft must accommodate both sides; the panel is more likely to warp during curing.

Application: place panel edges at curvature-discontinuity lines, not across them. The decomposition looks for Gaussian curvature changes and aligns panel edges accordingly.

Principle 4: Match the Crane and Access

Each panel must be hoistable by the crane that will be on site. The decomposition must respect the crane's capacity at the relevant radius:

• Typical tower crane: 5–10 tonne capacity at 30 m radius
• Typical truck crane: 20–50 tonne capacity at 10–20 m radius
• Manual / chain hoist (low-rise): 1–3 tonne capacity

A panel sized for visual aesthetics but exceeding the crane capacity has to be redesigned on site — a costly outcome. The decomposition should verify crane capacity per panel before the design is frozen.

Principle 5: Per-Piece Weight Limit (The Hard Rule)

Beyond crane capacity, per-piece weight limits are driven by:

• Standard factory handling: panels over 500 kg typically require forklift or crane handling at the factory, adding cost and slowing production
• Standard truck transport: panels over 1,500 kg require special transport permits and often a dedicated truck, doubling transport cost
• On-site handling: panels over 800 kg typically need a separate crane support at the installation point, in addition to the main hoist
• Connection node design: heavier panels need stronger brackets, more anchor points, often larger steel framing — the cost compounds

Standard limit: 500 kg per panel for normal GRC components. Soft limit: 800 kg per panel with explicit crane and connection verification. Hard limit: 1,500 kg per panel, requiring special transport, hoisting protocol, and connection design — typically only for signature landmark projects where the visual outcome justifies the cost.

The decomposition should target ≤500 kg as the default and only exceed it when the design requires it.

The Weight Calculation

GRC panel weight calculation:

Weight (kg) = Length (m) × Width (m) × Thickness (mm) × 2.1 (kg/m²/mm)

For a 1.5 m × 1.0 m × 15 mm panel: 1.5 × 1.0 × 15 × 2.1 = 47 kg. Well within the standard limit.

For a 3.0 m × 1.5 m × 25 mm panel: 3.0 × 1.5 × 25 × 2.1 = 236 kg. Within the soft limit.

For a 4.0 m × 2.0 m × 40 mm panel: 4.0 × 2.0 × 40 × 2.1 = 672 kg. Over the standard limit; needs explicit verification.

How the Five Principles Interact

The five principles sometimes conflict. Common trade-offs:

• Modular vs hide-in-weak-spot: a modular repeat may force joints on a smooth surface. Resolution: accept the visual joint, or break the modularity.
• Per-piece weight vs visual: a single large panel may look better but exceed the weight limit. Resolution: split the panel along a feature line, accepting one more joint.
• Avoid curvature-discontinuity vs crane capacity: a panel that respects a curvature change may still exceed the crane capacity. Resolution: split at the curvature change into two smaller panels.

The deepening designer's job is to document the trade-offs explicitly and get sign-off from the architect and the installation team before the design is frozen. Trade-offs discovered on site are 5–10× more expensive to fix.

Decomposition Documentation

Every decomposition decision should be documented in the deepening drawings:

• Panel-by-panel weight, CG, dimensions
• Panel-by-panel mould assignment (which mould fabricates which panel)
• Joint pattern with joint width and sealant specification
• Hoisting sequence with crane position per panel
• Installation tolerance per panel

The documentation is the basis for the factory's production planning and the installation team's site planning. Missing documentation is the single biggest source of cross-team misunderstandings.

Bottom Line

Five principles govern good GRC panel decomposition: hide joints in weak spots, modularise where possible, avoid curvature-discontinuity within a panel, match the crane, and respect the per-piece weight limit. The principles interact; trade-offs are inevitable and must be documented. The default per-piece weight limit is 500 kg; exceeding it requires explicit verification across factory, transport, and installation.

A good decomposition makes the project invisible — the joints disappear, the installation flows, the curve closes. A bad decomposition makes the project about the joints.

Guangdong Qinglong Construction's deepening team applies the five-principle decomposition to every complex-shaped GRC project. Visit the official website for sample decomposition drawings and weight calculation templates.