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Regarding the waiting time before plastering after the construction of exterior wall insulation, the core principle is to allow the wall to settle and dry completely to avoid quality problems such as cracking and delamination of the subsequent plaster layer. Specific requirements vary depending on the wall materials, season, and regional regulations.
I. Main Specifications and Time Requirements
Although it is generally recommended to wait several days for wall construction, for projects with higher quality requirements (especially base walls prepared for external insulation construction), the waiting time is usually longer and subject to specific technical regulations.
Core Standard: According to a process control standard in the industrial construction field, plastering work should be carried out no less than 15 days after the completion of the masonry work. This is to control the moisture content of the wall and prevent cracking of the plaster layer due to excessive drying shrinkage.
Winter Construction: If construction takes place in winter, this waiting period needs to be extended to at least 30 days. This is because in low-temperature environments, the time required for wall moisture evaporation and material stabilization is significantly increased.
Local and Company Standards: For your specific project, you must prioritize consulting and complying with the local engineering construction standards, design drawing requirements, and the general contractor's company process standards. These documents may have more specific or stricter regulations regarding the waiting time.
II. Key Factors Affecting Waiting Time
In addition to adhering to strict time regulations, the following factors must be considered during construction to determine whether the wall is truly ready for plastering:
Wall materials: Different building blocks (such as aerated concrete blocks and concrete hollow bricks) have different water absorption and shrinkage rates, resulting in varying drying times.
Climate and environment: Temperature, humidity, and ventilation directly affect the drying speed. Longer waiting times are required during the rainy season or in high-humidity environments; during hot and dry summer months, care must be taken to prevent the wall from drying out too quickly.
Structural location: The top of the wall where it meets the beam and slab is a point of stress concentration and prone to cracking. Standards require that when the infill wall is built to near the bottom of the beam or slab, a gap should be left, and the diagonal bracing should be tightened at least 14 days after the completion of the masonry work. Only after this process is completed and stabilized can the overall plastering work begin.
III. Inspection and Preparation Before Plastering
After the required waiting period, the following inspections and preparations must be completed before formal plastering:
Inspect wall stability: Observe the wall for uneven settlement or cracks. Conduct necessary on-site inspections, such as checking whether the tie bars are installed according to the design requirements.
Address base defects:
Fill any loose areas or gaps with insufficient mortar on the wall surface with cement mortar.
Remove dust, oil stains, etc., from the wall surface and moisten it appropriately in advance (different wall materials have different wetting requirements; for example, aerated concrete block walls need to be sprayed with water using a sprayer before applying the base coat).
Perform technical treatments:
At the junction of different wall materials (such as masonry and concrete structures), anti-cracking steel mesh or alkali-resistant fiberglass mesh must be installed to prevent cracking.
The pre-embedded pipe trenches in the wall should be repaired and leveled with cement mortar, and anti-cracking treatment should be applied.
IV. Professional Advice and Common Problems
Avoid rushing the construction schedule: Under no circumstances should you shorten the necessary waiting time to meet deadlines. This is fundamental to ensuring the quality of the exterior walls and preventing leaks and peeling.
Pay attention to critical points: In addition to the wall itself, pay special attention to critical areas such as the eaves and the upper parts of window openings. These areas must be fitted with drip grooves as required to prevent rainwater from flowing back.
Material quality control: The mortar used for plastering must meet the required strength specifications, and the use of substandard fine sand or stone powder is strictly prohibited.
