Comprehensive Guide to Plastering: Base Treatment, Material Selection, and Quality Control

Preparation of the Plastering Base Surface：Before plastering, the base surface must be thoroughly cleaned and moistened. Dust, oil stains, salt deposits, and alkali efflorescence on brick walls and concrete surfaces should be completely removed. For oil stains, a 5%–10% sodium hydroxide (caustic soda) solution can be used first, followed by rinsing with water. For salt and alkali residues, a 3% oxalic acid solution is recommended. Any protruding areas on concrete should be chiseled flat, and all construction holes, including (wall-penetrating bolt) holes, must be sealed tightly according to specifications. In addition, steel wire mesh or fiber mesh should be installed at junctions where different materials meet (e.g., masonry walls and concrete columns) to prevent cracking.

Material Selection and Application Techniques：Only qualified Portland cement with a strength grade no less than 32.5MPa should be used, along with matching sand and additives. The use of “Mortar King” is strictly prohibited. During winter, antifreeze admixtures can be added to ensure the plaster doesn’t freeze during its early hardening stage. Before applying the plaster, the wall should be evenly sprayed with water until moisture penetrates approximately 8–10mm into the masonry. A final watering should be done about one hour before plastering. A 2mm layer of plain cement slurry should be applied to the concrete surface as a bonding coat to improve adhesion.

Reinforcement and Quality Control Measures：To further prevent cracking, additional steel wire mesh must be installed in key areas such as around cable troughs, distribution boxes, and fire hydrant boxes. The mesh should be embedded within the plaster layer rather than directly attached to the wall surface, with an overlap width of no less than (100mm + cable trough width + 100mm). After applying the base coat, it’s recommended to wait at least 24 hours before applying the finish coat. Any hollow spots or cracks found in the base layer should be repaired before proceeding. During construction, protect finished surfaces such as aluminum frames, floor finishes, and pre-installed equipment from damage or contamination.