Longitudinal Cracks in Prefabricated Slabs of Old Houses

Longitudinal cracks in the prefabricated slabs of old houses require assessment of their causes based on specific circumstances and the implementation of corresponding measures. In most cases, they do not affect structural safety and can be resolved through filling, reinforcement, or renovation.

Longitudinal cracks in the prefabricated slabs of old houses commonly arise from factors such as excessive bottom loads, insufficient concrete strength, and loose connections between the slabs and the foundation. If the cracks are straight and located in the gaps between the slabs, they are relatively common in brick-and-concrete floor houses and typically represent normal phenomena inherent to the house's structure, generally not posing a significant threat to the overall structural safety of the house. For such cracks, the simplest and most direct treatment method is to use materials like lime paste to fill the cracks and restore surface smoothness.

If cracks appear at the bottom of the prefabricated slabs and require resolution of the cracking issue, the following measures can be taken:

• Reinforce bottom strength: Install reinforcing bars or use thick steel plates at the bottom of the prefabricated slabs to increase structural load-bearing capacity, disperse local stress, and reduce the risk of crack propagation.
• Improve concrete quality: Optimize the concrete mix ratio, such as adjusting the types or proportions of materials added, and strictly control the water-cement ratio to prevent cracking due to concrete shrinkage or insufficient strength.
• Enhance connection stability: Install reinforcing bars or adopt other reinforcement methods at the connection points between the prefabricated slabs and the foundation to strengthen the overall structural stability and reduce cracks caused by loose connections.
• Regular maintenance: Regularly clean the surfaces of the prefabricated slabs, remove dust and debris, and apply waterproof paint to prevent water penetration and erosion of the concrete, thereby delaying the aging process.

If the cracks are located at the intermediate joints of the prefabricated slabs, they typically represent inherent characteristics of the house's structure and generally do not require structural reinforcement. However, to enhance the user experience and aesthetics, the following measures can be taken during renovation:

• Wall crack treatment: Hang fiberglass mesh at the cracks to conceal them by enhancing the bond between the material and the wall, while also preventing further cracking.
• Floor crack treatment: For floor cracks, simple waterproofing measures should be taken, such as applying waterproof coatings or laying waterproof membranes, to prevent water from seeping through the cracks into the lower floors or damaging the flooring materials.