GFRG Panel Calculator: Complete Design Guide
What are GFRG Panels?
Glass Fibre Reinforced Gypsum (GFRG) panels are large-format load-bearing wall elements cast from high-strength alpha-gypsum reinforced with alkali-resistant glass fibre rovings. Standard panels are 3.0 m long × 0.6 m high × 124 mm thick (approximately 40 kg each) and contain 15 hollow rectangular cavities running the full panel height.
GFRG construction offers rapid assembly — experienced crews can erect 80–120 m²/day. The hollow cavities are selectively filled with concrete and rebar to create structural columns, enabling load-bearing wall systems for multi-storey buildings.
Panel Schedule & Cavity Fill
Panel count = ⌈Net Wall Area ÷ (3.0 × 0.6)⌉ × Waste Factor. Each panel covers 1.8 m². Standard waste allowance is 5–7% for residential projects. Cavity fill volume = cavities × cavity volume (50×124 mm cross-section) × panel count × fill ratio.
Structural Design & Rebar
Vertical N10 bars in alternate cavities (50% fill) is the standard structural specification for residential load-bearing walls. Axial capacity: P = 0.6 × f'c × Ac + fy × As, reduced by slenderness factor for H/t ratio. Panel thickness is 124 mm — maximum wall height without engineering review is approximately 3.7 m (H/t = 30).
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Thermal, Acoustic & Fire Performance
Unfilled GFRG panels (λ ≈ 0.35 W/mK) give U ≈ 1.9 W/m²K — external insulation is needed for energy code compliance. STC ranges from 32 dB (unfilled) to 45 dB (fully filled). Fire resistance: unfilled 30 min, 50% filled 60 min, fully filled 90–120 min. Each 10 mm plaster per face adds 30 minutes.
FAQs
How many GFRG panels do I need per m²?
Standard GFRG panels are 3.0 m × 0.6 m = 1.8 m² each. You need approximately 0.56 panels per m² of wall face. Add 5–7% waste for cuts at openings and corners. Panels cut at window sill height can often be reused above the opening.
What concrete is used to fill GFRG cavities?
Self-compacting concrete (SCC) with maximum 10 mm aggregate is specified for GFRG cavity fill. Standard strength is 40 MPa for residential. Pour the concrete in maximum 600 mm lifts to control pressure on the gypsum shell. Vibration is not required with SCC.
What is the U-value of a GFRG wall?
Unfilled GFRG gives U ≈ 1.9 W/m²K (λ = 0.35 W/mK). Fully filled gives U ≈ 4.8 W/m²K (worse — concrete is a good conductor). For energy compliance, add 50 mm XPS to achieve U ≈ 0.55 W/m²K or 75 mm EPS for U ≈ 0.40 W/m²K.
Is GFRG construction faster than traditional masonry?
Yes — significantly. GFRG crews can erect 80–120 m² per day versus 15–25 m²/day for brickwork. The 3.0 m × 0.6 m panels cover large areas quickly. Reduced formwork, integrated finish, and faster cycle times typically allow a GFRG structure to be weatherproofed 4–6 weeks sooner than equivalent CMU or framed construction.