What is the allowable range of flatness deviation for GRC exterior walls?

According to the "Standard for Quality Acceptance of Building Decoration Engineering" (GB50210), the allowable deviation for GRC exterior wall flatness is 4mm/2m. However, Qinglong often implements a stricter corporate standard of 3mm/2m on super high-rise projects.

Deviation control must start from the source—mold precision. Steel molds are machined with CNC machine tools to ensure the master mold's flatness error is ≤1mm. The Shanghai Xinghewan project adopted this technology, keeping the warpage deformation of individual panels within 0.1% of panel length.

During the installation stage, 3D laser scanning technology is applied. By comparing point cloud data with the BIM model, hanger positions are adjusted in real time. The hyperbolic curtain wall project of the Guangxi New Media Center ultimately achieved a flatness of 2.5mm/2m, far exceeding the national standard.

Environmental temperature effects require dynamic compensation. Precision measurements should be avoided at midday under intense sunlight; instead, work is scheduled in the early morning when temperatures are stable. Experience from the Zhuhai Chimelong project shows this measure can eliminate measurement errors of 2-3mm caused by temperature differences.