Cracks in Prefabricated Panel Houses Over Time

When cracks appear in prefabricated panel houses over time, targeted treatment measures should be taken based on the crack conditions, as follows:

1. Unidirectional parallel cracks: No structural risk but need for leakage prevention If the cracks are unidirectional and parallel to one side of the wall, they are usually caused by the asynchronous deformation of two prefabricated panels. When there is no significant deflection in the floor slab (i.e., no bending or sagging), such cracks generally do not affect the structural safety of the house but may cause leakage problems. In this case, there is no need for structural reinforcement, but regular checks should be made to see if the cracks are expanding, and attention should be paid to whether there is water seepage during the rainy season. If leakage is found, follow the subsequent repair steps.

2. A small number of tiny cracks: Can be left unrepaired for now but need observation When there are few cracks, the gaps are narrow (usually less than 0.2 millimeters wide), and there are no traces of liquid flow on the floor, such cracks have minimal impact on structural safety and can be left unrepaired for now. However, regular observation of the crack changes is required. If the crack width continues to increase or the number of cracks increases, the risk needs to be reassessed. In daily use, avoid stacking heavy objects or applying impact forces in the crack area to prevent the cracks from expanding.

3. Leaking cracks: Require immediate repair and standardized operation If the cracks are slightly larger (more than 0.2 millimeters wide) and there is liquid leakage, repair them according to the following steps:

• Chiseling the cracks: Chisel open the panel seams of the cracks, chisel away 5 centimeters of the surface layers on both sides to make the joint surface slope-shaped, and appropriately chisel the surface of the prefabricated floor slab and the sides of the panel, and clean up the debris and dust.
• Applying cement slurry: Brush a layer of pure cement mortar inside the panel seams, with a water-cement ratio controlled between 0.4 and 0.5, to enhance the bonding strength between the new and old concrete.
• Pouring fine aggregate concrete in layers: Pour for the first time to half the depth of the panel seams, wait for the fine aggregate concrete to absorb water for a moment, and then pour for the second time until it is compacted and leveled 1 centimeter from the floor surface to avoid voids.
• Curing and protection: After the repair is completed, cure for at least 2-3 days. During this period, stepping on or stacking heavy objects is strictly prohibited to ensure the full hardening of the concrete.

4. Crack treatment during the renovation period: Prioritize the use of reinforcement materials During renovation, for existing cracks, first fill the gaps inside with filling materials, and then paste Dacron cloth or mesh cloth on the outer layer to enhance crack resistance. If the cracks are more serious, carbon fiber cloth can be added. Its high-strength property can effectively inhibit crack expansion. During construction, ensure that the base layer is dry and clean, and the filling materials and reinforcement materials are firmly bonded.

5. Construction taboos: Avoid damaging the load-bearing structure of the floor slab When dealing with cracks, drilling holes in the prefabricated panels is strictly prohibited to avoid weakening the load-bearing capacity of the floor slab. If ceiling construction is required, the hanging rods must be installed in the seams between two prefabricated panels and fixed with special connectors to ensure construction safety.