Cracks in Prefabricated Panel Houses

Whether cracks in prefabricated panel houses are normal requires a comprehensive assessment based on the type, characteristics of the cracks, and the actual situation of the house. Here are common types of cracks and corresponding handling suggestions:

1. Unidirectional cracks parallel to one side wall
These cracks are usually caused by the asynchronous deformation of two prefabricated panels. If there is no significant deflection (such as sagging or bulging) in the floor slab, there is generally no safety hazard, but attention should be paid to the issue of rainwater leakage. The cracks run parallel to the wall, are generally narrow in width, and are mostly caused by material shrinkage or local stress concentration.

2. Shrinkage cracks and temperature cracks

• Shrinkage cracks: During the manufacturing process, the hydration reaction of cement causes volume shrinkage. When the shrinkage stress exceeds the tensile strength of the concrete, shrinkage cracks form. The width of these cracks is mostly between 0.05 and 0.2 millimeters, evenly distributed, appearing as fine mesh or irregular shapes, and have a relatively small impact on structural safety.
• Temperature cracks: Changes in ambient temperature cause the prefabricated panels to expand and contract thermally, generating temperature stress under structural constraints. These cracks are commonly found on the top floor of houses, often distributed in a regular diagonal or horizontal pattern, and may become more pronounced in winter due to increased temperature differences. These cracks usually do not accompany structural deformation, but attention should be paid to waterproofing.

3. Settlement cracks and steel bar corrosion cracks

• Settlement cracks: When slight uneven settlement occurs in the house foundation, the prefabricated panels may develop cracks due to stress concentration. These cracks are relatively wide (possibly exceeding 0.3 millimeters), extending from the bottom to the top of the panel, and their direction is consistent with the settlement trend. A comprehensive assessment should be made in conjunction with abnormalities such as house tilt and window and door deformation. If the cracks continue to develop, timely inspection and reinforcement are required.
• Steel bar corrosion cracks: When the steel bars inside the floor slab corrode, their volume expands, causing the concrete to crack. These cracks are distributed along the direction of the steel bar arrangement, appearing as straight horizontal and vertical lines, and rust marks can be seen on the surface of the panel. These cracks will expand over time and may even cause the steel bars to rust and break, significantly reducing the load-bearing capacity of the floor slab. Immediate durability repairs are required.

4. Abnormal situations to be vigilant about
If the crack width exceeds 0.3 millimeters, continues to expand, or is accompanied by floor slab deflection (visible deformation), through cracks in the interior with a width greater than 0.7 millimeters, house tilt, and other abnormalities, it may involve structural safety issues. A professional organization should be commissioned to conduct inspection and appraisal, and reinforcement measures should be taken if necessary.

5. Renovation handling suggestions
During renovation, first fill the cracks with filling materials, then paste Dacron cloth or mesh cloth on the outer layer to enhance crack resistance, and finally cover with carbon fiber cloth to improve the overall structural integrity. For severe cracks, structural defects should be repaired before renovation.