Cracks in Prefabricated Houses

The hazards of cracks in prefabricated houses need to be comprehensively evaluated based on the type, location, and width of the cracks. Some cracks may affect structural safety and require prompt attention.

I. Types of Cracks and Hazard Analysis

1. Unidirectional Parallel Cracks
   If the crack is unidirectional and parallel to one side of the wall, it is usually caused by the asynchronous deformation of two prefabricated panels. In cases where there is no significant deflection (i.e., no bending or sinking) of the floor slab, such cracks generally pose no safety hazard but may lead to rainwater leakage through the gaps, necessitating attention to waterproofing.

2. Stress Cracks
   If cracks appear in stress-bearing areas (such as horizontal cracks when the roof sags), caution is required even if the width is only 0.8 millimeters. If the crack width exceeds 1 millimeter (equivalent to twice the thickness of a bank card), or extends from the roof to two-thirds of the wall height, or is located on a load-bearing beam, the risk factor increases significantly, potentially threatening structural safety.

3. Shrinkage Cracks
   Caused by concrete shrinkage, these cracks are often found at the corners of floor slabs or in areas with weak constraints. If the crack width is not large (usually less than 0.3 millimeters), it generally does not affect structural safety but may reduce the durability of the concrete, requiring attention to whether the cracks continue to expand.

4. Reinforcement Corrosion Cracks
   Distributed along the direction of reinforcement placement, with visible rust marks on the surface. Such cracks will gradually expand over time until the reinforcement rusts and breaks, reducing the load-bearing capacity of the floor slab and requiring durability repairs; otherwise, structural damage may occur.

II. Treatment Recommendations

1. When Cracks Do Not Develop

• Fine cracks (width less than 0.3 millimeters) can be sealed with glue to prevent water intrusion.
• Medium cracks (width 0.3-1 millimeters) require injection of special adhesive (which takes 72 hours to dry) to enhance the overall structural integrity.

2. When Cracks Continue to Develop

• If the cracks lengthen or widen, or if visible deflection or deformation occurs, immediately contact a professional agency for inspection and assessment.
• If indoor cracks penetrate and the width is greater than 0.7 millimeters, there may be serious safety hazards, requiring reinforcement treatment (such as pasting carbon fiber sheets or adding supports).

Note: Crack treatment should be based on the specific type and location. Non-professionals should not attempt to repair cracks in stress-bearing areas or load-bearing components by themselves to avoid secondary risks.