What Is the Allowable Range of Flatness Deviation for GRC Exterior Walls? Flatness Deviation Standards and Control Measures

Flatness deviation of GRC exterior walls directly affects the building's appearance and installation quality. Excessive deviation can easily cause problems such as uneven joint gaps, seal failure, and unbalanced loading, so the deviation range must be strictly controlled in accordance with industry standards. Drawing on its high-precision production and installation experience, Qinglong explains the allowable flatness deviation range and control solutions.

I. Core Standard Requirements for Flatness Deviation of GRC Exterior Walls

According to the Technical Standard for Application of Glass Fiber Reinforced Cement (GRC) in Buildings (JGJ/T423-2018), flatness deviation is clearly regulated. Surface flatness of individual GRC components: tested with a 2m straightedge, the allowable deviation is ≤3mm/m and the full-length deviation ≤5mm; the flatness deviation of GRC components produced by Qinglong can be controlled within 2mm/m, far exceeding the standard requirements; flatness of joints between components: the surface level difference between adjacent components has an allowable deviation of ≤2mm, and the joint width deviation is ≤1mm, to avoid step-like protrusions; overall wall flatness: within every 10m range, the verticality deviation is ≤5mm and the flatness deviation ≤8mm, ensuring a coordinated overall visual effect; shaped components (such as double-curved surfaces and curved panels): the curvature radius deviation is ≤3mm, with a smooth surface free of noticeable bumps or depressions.

II. Analysis of Key Factors Affecting Flatness Deviation

Deviations arise throughout the entire process of production, transportation, and installation, and require precise control. Production stage: insufficient mold precision (surface flatness deviation >1mm), uneven vibration causing surface irregularities on components, and deformation during curing can all lead to deviation; transportation stage: failure to use dedicated transport racks during GRC component transport, or insecure fixing leading to compression deformation—especially for oversized components, the risk of deformation in transit is higher; installation stage: unevenly installed base keels, elevation deviation of anchoring points, and lack of precise calibration during installation can all cause wall flatness to exceed the standard; environmental factors: exposure to high temperatures and soaking by rainwater cause later deformation of components, affecting flatness stability.

III. Flatness Control Measures in Production and Installation

Refined control throughout the entire process ensures that deviations meet the standards. Production control: high-precision steel molds are adopted, with mold surface flatness deviation ≤0.5mm/m, plus regular inspection and maintenance; automated vibration equipment ensures a dense, uniform slurry with a smooth surface; standardized curing avoids deformation caused by drastic temperature and humidity changes. Qinglong achieves precise control of component flatness through its automated production lines. Transportation control: customized dedicated transport racks are used, with components fixed upright and support points evenly distributed to avoid squeezing and collision; shock-absorbing measures are adopted for long-distance transport to reduce deformation from jolting. Installation control: the flatness of the base keel is calibrated before installation, with deviation ≤2mm/m; 3D laser positioning technology precisely adjusts component positions to ensure elevation and verticality meet requirements; prompt inspection follows installation, and any deviation found is adjusted immediately. In the Guangzhou Dongzhu Shangdu project, Qinglong achieved zero flatness overrun in installation through this approach.

IV. Detection and Rectification Solutions for Flatness Deviation

Strict detection and timely rectification safeguard construction quality. Detection methods: a 2m straightedge combined with a feeler gauge is used to test the flatness of individual components, and a laser rangefinder tests the verticality and flatness of the overall wall; at least 3 points are measured on each component, and 1 cross-section is measured per 10m of wall; rectification measures: for minor deviations (≤4mm), correction is achieved by grinding and repairing the surface, using special repair mortar to ensure a smooth surface after repair; for larger deviations (>4mm), component positions must be adjusted or components replaced, followed by reinstallation and recalibration; acceptance criteria: all flatness deviations comply with the specification requirements, joints between adjacent components are smooth, and the overall wall presents a coordinated visual effect. Qinglong has established a dedicated flatness acceptance process to ensure a 100% acceptance pass rate.