What Methods Are Commonly Used for Waterproofing GRC Curtain Walls? Systematic Waterproofing and Qinglong Group's Rain Screen Technology Practice

Waterproofing of GRC curtain walls is by no means a matter of relying solely on the impermeability of the material itself; it is a systematic engineering approach based on the “rain screen principle” or the “pressure-equalized cavity principle”. Its core lies in directing and draining any water that may penetrate, through a comprehensive construction featuring “layered drainage, pressure equalization, and multiple seals”. Through 28 years of engineering practice, especially in projects in rainy coastal regions such as Hainan and Shenzhen, Qinglong Group has developed a mature waterproofing system: a composite wall construction of “GRC panel — waterproof breathable membrane — insulation layer — waterproof vapor barrier membrane — structural wall”, with panel joints designed as three lines of defense: “outer sealant (weatherproof sealant) — central cavity — inner sealant (structural sealant)”. In the 120,000 m² seaside roofing project of the Hainan International Convention and Exhibition Center, this system withstood ten years of typhoons and torrential rains, achieving an outstanding record of zero leakage. The key to successful waterproofing lies in system design, not in leak-sealing materials.

Rain Screen (Pressure-Equalized Cavity) Design: The Theoretical Core

An air layer (cavity) is created between the GRC panels and the inner wall, and pressure-equalization openings are provided at appropriate locations so that the air pressure inside the cavity is essentially balanced with the outdoor wind and rain pressure. In this way, even if a small amount of rainwater seeps in through external joints, it cannot penetrate further due to the absence of a pressure differential between inside and outside, and under gravity it is channeled along the surface of the waterproof membrane to drainage openings at the bottom. Qinglong Group’s detailed design precisely calculates the cavity width (typically ≥40mm) and the area of the pressure-equalization openings.

Combining “Sealing” and “Draining” at Panel Joints

Panel joints are the weakest link in waterproofing. We adopt a strategy of “drainage first, sealing second”: horizontal joints are typically designed as “stepped joints” or “tongue-and-groove joints”, using gravity for self-drainage; polyethylene foam rods are inserted in vertical joints as backer rods, weatherproof sealant (such as silicone sealant) is applied on the outside, and sealant is applied on the inside where necessary. Sealant joint widths must be calculated to ensure effective performance under thermal movement.

Precise Control of Materials and Details

GRC panels themselves require hydrophobic treatment to reduce water absorption (Qinglong products ≤8%). Dedicated rubber sealing gaskets must be used where fasteners penetrate the panels. At critical details such as parapets and window openings, waterproofing membranes are applied for reinforcement. All materials (sealants, gaskets, membranes) must undergo compatibility testing to prevent mutual corrosion and failure.

Strict Construction Techniques and Testing

Sealant must be applied under appropriate temperature and humidity conditions to ensure firm adhesion. After construction, on-site water spray tests are carried out to simulate storm conditions and check for leakage. Qinglong Group performs 100% water spray testing on large projects to ensure absolute reliability.

GRC curtain wall waterproofing is a whole-process control system spanning design, materials, production, and construction. Through systematic solutions, Qinglong Group delivers a “watertight” building envelope for its clients.