In plastering applications using dry-mix mortar, issues such as hollowing, cracking, and debonding continue to challenge construction sites, and repeated repairs often fail to provide lasting results. In reality, these problems are rarely caused by a single factor; instead, they result from the combined effects of material performance, construction practices, and environmental conditions. Based on extensive field experience, the most common risks originate from poor substrate preparation and insufficient pre-treatment. If the wall surface is not properly cleaned or repaired, dust, oil, and voids can create separation layers that significantly reduce bonding strength. At the same time, insufficient pre-wetting allows the substrate to absorb water too quickly, disrupting cement hydration and leading to inadequate strength development and weak adhesion, ultimately increasing the likelihood of hollowing and cracking.

During application, improper construction practices further amplify these risks. Excessive thickness in a single layer or poor timing between layers can lead to plastic shrinkage and stress concentration, especially when the base layer has not fully set before the next layer is applied, effectively behaving as a single thick application prone to defects. Another common misconception is increasing mortar strength by adding more cement; although this may improve early strength, it also raises heat of hydration and shrinkage stress, ultimately increasing cracking risk. In addition, poor mix design—such as excessive binder content, low sand ratio, or improper grading—can significantly increase shrinkage. Inadequate interface treatment is another critical issue; when bonding layers are inconsistently prepared, overly diluted, or lack sufficient roughness, they fail to provide effective mechanical interlocking, leading directly to debonding between the plaster layer and the substrate.

From a system control perspective, preventing hollowing and cracking requires a coordinated approach. Proper substrate cleaning, repair, and pre-wetting must be ensured before application; during construction, layer thickness and timing should be carefully controlled to avoid single-pass buildup; in terms of materials, cement and total binder content must be optimized, with proper sand ratio and grading, supported by stable additive systems; interface treatment should rely on standardized products and methods to ensure adequate bonding strength and roughness; and curing must be maintained for at least seven days to prevent early moisture loss. In challenging environments such as basements with poor ventilation, additional adjustments to formulation and application timing are necessary. Only by aligning materials, construction processes, and environmental conditions can hollowing and cracking be effectively minimized and long-term performance achieved.