Key Points of Drainage Design for Single-Curved GRC Panels Used on Roofs?

When single-curved GRC panels are applied to roofing systems, drainage design is the key to ensuring long-term functionality and preventing leakage. The design must comprehensively consider four major elements: "panel layout, joint construction, slope control, and drainage paths". Qinglong Group has accumulated extensive drainage design experience through large roofing GRC projects such as the Hainan International Convention and Exhibition Center.

The arrangement direction of panels and joint design should facilitate drainage. Typically, the arch height direction of single-curved panels is aligned with the main drainage direction of the roof, forming natural drainage channels. The transverse joints between panels (perpendicular to the drainage direction) are the weak points of waterproofing and must be designed using the "rainscreen principle". Qinglong's approach is to establish multiple lines of waterproofing defense: weather-resistant sealant is applied to the outside of the joint as the first line of defense; a physical cavity is set on the inside to block capillary action; drainage holes are provided at the bottom of the cavity to drain away any small amount of rainwater that may penetrate. Longitudinal joints (parallel to the drainage direction) can be treated with lapping or covered with dedicated flashing.

Roof slope control is the foundation for smooth drainage. Even when single-curved panels are used to form a natural curvature, the entire roof must have a sufficient overall drainage slope, usually no less than 2%. During detailed design, Qinglong uses BIM models to perform roof drainage analysis to ensure there are no ponding areas. For areas with smaller slopes, the panel arch height is appropriately increased to enhance drainage capacity. All drainage paths should be clear and short, directing water straight to gutters or downpipes.

Waterproofing treatment of detail nodes is critical. The intersections between the roof and vertical elements such as parapet walls, skylights, and equipment bases are areas prone to leakage. At these locations, Qinglong designs metal flashing or stainless steel waterproofing membranes to flexibly connect the GRC roof with the vertical elements; the flashing should extend sufficiently behind the wall or element and be sealed with weather-resistant sealant. Around all elements penetrating the roof (such as support bolts), dedicated waterproof sealing kits should be used. Qinglong recommends that after the roofing GRC system is installed, continuous water spraying tests should be conducted to simulate heavy rainstorm conditions and verify the effectiveness of the drainage design, ensuring a foolproof result.