3. Seepage caused by cracks in external lightweight masonry walls: The temperature expansion coefficient of lightweight bricks used in external walls for filling rather than load-bearing purposes is greater than that of clay bricks. Therefore, after the alternation of winter and summer or sudden temperature changes when it rains after intense sunlight, cracks will inevitably appear between the lightweight bricks and the concrete frame beams and columns. Additionally, lightweight bricks also have unfavorable factors for waterproofing such as large shrinkage deformation, high water absorption, low surface strength, and a tendency to produce powder.
4. Seepage caused by poor exterior wall decoration construction: Irregular or non-straight plastering joints on exterior walls, or residual mortar not being cleaned up, can cause rainwater to accumulate within the joints. Embedding the joint strips too deep leads to insufficient thickness at the bottom of the joints, allowing rainwater to seep into the walls. Holes and gaps on the walls are not carefully sealed before attaching tiles on the exterior walls; improper grouting between decorative tiles or low-grade mortar forming capillary pores can lead to seepage under wind pressure.
5. Seepage caused by loose sealing around door and window openings.