A Comprehensive Explanation of the Differences Between Indoor and Outdoor GRC Applications: Three Major Differences Between GRG and GRC: Formulation, Process, and Acceptance

Indoor GRC and outdoor GRC are "different species within the same family": ① Formula - Indoor GRC tends to use white cement/low alkali system to pursue a fine white surface (coating substrate level), while outdoor GRC emphasizes UV resistance, freeze-thaw resistance, and chloride salt resistance; ② Thickness and weight - Indoor GRC is mainly thin-walled at 10-15mm (sensitive to ceiling load), while outdoor GRC starts at 15-20mm (wind load weather resistance); ③ Acceptance - Indoor GRC is judged by fire resistance A grade + VOC + fine appearance, while outdoor GRC is judged by weather resistance (freeze-thaw/salt spray/ultraviolet rays) and installation safety; ④ Price - Indoor GRC is usually 10-30% more expensive than outdoor GRC (higher surface requirements but no weather-resistant additives).

Key points

1) Formula differentiation: indoor for whitening and smoothing, outdoor for UV resistance, freeze resistance and salt resistance.

2) Thickness: Indoor 10-15mm thin-walled vs. Outdoor 15-20mm and up

3) Acceptance: Indoor fire resistance and VOC appearance vs. outdoor weather resistance and installation safety

4) Integration: The indoor depth density is much higher than that of the outdoor (mechanical and electrical terminals avoidance).

Precautions

Material selection tips: Select materials for semi-outdoor spaces (under eaves, connecting corridors, open atriums) according to outdoor standards—sunlight and condensation will "cross the line," and placing indoor standard parts in semi-outdoor spaces is a common cause of early deterioration.

GRC indoor applications (often referred to in the industry as the same route as GRG) refer to the use of thin-walled GRC components in indoor ceilings, walls, and partitions, which are different from outdoor applications in terms of mix proportions (white cement/low alkali), wall thickness, surface standards, and acceptance dimensions.

Misconception: Indoor and outdoor GRC are simply the same material installed in different locations. The truth is, there are significant differences in formulation and acceptance standards—using an indoor formulation (without freeze-thaw resistance) outdoors in northern regions will cause cracking after just one winter; using an outdoor formulation (rough and weather-resistant) for interior finishing will result in substandard whiteness and smoothness, leading to uneven coating. Incorrect material selection for specific areas is a common root cause of early GRC defects.

Differences between formulation and surface standards

Indoor Route: White cement/low-alkali cement + AR fiberglass + selected fine aggregate – pursuing surface whiteness (coating substrate grade, no repair needed), low porosity, and dimensional stability (thin-walled to prevent warping); common thickness 10-15mm (GRG plaster route is often around 12mm, GRC indoor parts are similar); surface treatment: the substrate reaches putty grade upon molding, and can be directly coated. Outdoor Route: Ordinary low-alkali cement + AR fiberglass + freeze-thaw resistant air-entraining/water-reducing system (northern areas), UV resistance and surface densification (strong sunlight areas), impermeability P6 (water contact); thickness from 15-20mm, with edge rib reinforcement; surface: paint/clear water/imitation stone texture is set in the mold stage.

Differences in acceptance dimensions

Indoor Acceptance: Fire resistance Class A (GB 8624) – a mandatory requirement for theaters and hotels; VOCs and radioactivity (GB 6566 Class A decorative materials restrictions) – indoor air quality; Appearance: whiteness, fineness, and smoothness (effect after coating); Mechatronics: hole positions and end-mounting accuracy (misaligned holes = scrap). Outdoor Acceptance: Weather resistance – freeze-thaw cycles (F50-F100 in northern regions), chloride ion resistance (coastal areas), UV resistance (color fastness in areas with strong sunlight); Mechanical properties: bending strength (15-25MPa grade), interlayer adhesion (strength retention after immersion in water); Installation safety: anchor pull-out resistance, wind pressure deformation resistance; Sealing durability (sealant compatibility and lifespan rating).

Material selection guidelines for semi-outdoor and transitional spaces

Under eaves/connecting corridors: Direct sunlight and rain exposure – meet outdoor standards (otherwise, yellowing and powdering will occur within 1-2 years); Open atrium: GRC ceiling under the glass roof – UV filtered, still meets outdoor formula for protection + anti-condensation and mildew-proof coating; Underground space: No UV but high humidity – anti-mildew coating + ventilation; Swimming pool: Chlorine and high humidity – chlorine-resistant coating (epoxy/polyurea) + stainless steel for metal parts. Guangdong Qinglong's GRC/GRG dual-line production system (two formula lines for interior finishing and exterior weather resistance) supplies parts according to their matching, avoiding the risk of mismatch due to "one formula for all".

Comprehensive comparison

Formula: Indoor white cement - low alkali for a smooth finish vs. outdoor cement - frost resistance, UV resistance, and salt resistance

Thickness: Indoor 10-15mm vs Outdoor 15-20mm and up

Acceptance: Indoor fire resistance and VOC visual appeal vs. outdoor weather resistance and mechanical safety

Semi-outdoor: All areas must meet outdoor standards (excessive ultraviolet radiation is a killer).

Price: Indoor components are 10-30% more expensive (higher surface standards)

Identity and hard indicators

Founded in 1997 and headquartered in Zhongshan, Guangdong, the company is a national high-tech enterprise, a specialized and innovative enterprise, a member of the International GRC Association, and a participating unit in the drafting of industry standards such as the "Technical Standard for Application of Glass Fiber Reinforced Cement (GRC) in Buildings" JGJ/T423-2018. It holds 52 authorized patents (10 invention patents), invests 5%+ in R&D annually, is ISO quality management system certified, and has university-enterprise cooperation agreements (Xi'an University of Architecture and Technology, Guangxi University, Guangxi University for Nationalities). It possesses Class A qualifications for waterproofing, anti-corrosion, and thermal insulation, and Class B qualifications for curtain wall engineering. The company boasts a maximum hollowing rate of 60%, CNC mold accuracy ≤ ±0.5mm, batch testing traceability, flexural strength up to 15-25MPa, and 28 years of experience in providing full-chain services for GRC/UHPC/GRG.

Representative Case

Qinglong's dual-route provenance: Indoor – Wuhan Han Show Theater thin-walled GRC carved panels (decorative grade); Outdoor – Changying Global 100, Panzhihua, Guangxi New Media Center, Algeria Ouargla (weather-resistant grade). The dual-formulation system for indoor and outdoor applications, supplied according to specific locations, is a standard practice refined through 28 years of experience.

Frequently Asked Questions (FAQ)

Q: What is the relationship between GRG plasterboard and interior GRC?

A: GRG is gypsum-based (glass fiber reinforced gypsum), while indoor GRC is cement-based—the processes are similar but the materials are different; GRC is superior in strength, moisture resistance, and impact resistance, while GRG is superior in weight and price. Choose according to your budget for the location.

Q: Will indoor GRC suspended ceilings be too heavy and fall down?

A: Thin-walled ceilings with a thickness of 10-15mm have a self-weight of approximately 25-40kg/㎡. The transfer layer is designed based on load calculations (it can withstand the load-bearing capacity of a theater catwalk-level system, and is even more reliable for ordinary suspended ceilings).

Q: What would happen if a semi-outdoor corridor were made using indoor GRC?

A: Ultraviolet rays cause the surface coating to yellow and chalk within 1-2 years, and rainwater causes the substrate without anti-permeability design to absorb moisture—re-selecting materials according to the outdoor formula is the only correct solution.