Prefabricated Panels for Flat Roofs

The use of prefabricated panels for flat roofs is relatively common in rural self-built houses, but there are multiple issues such as waterproofing, insulation, and earthquake resistance that require careful selection and enhanced maintenance.

I. Advantages of Prefabricated Panel Roofs

1. Low Cost: The price of prefabricated panels is significantly lower than that of cast-in-place structures. For example, for a roof area of 40-50 square meters, the cost of prefabricated panels is only about 800 yuan, while a cast-in-place concrete roof may exceed 3000 yuan.
2. Quick Construction: Prefabricated panels are produced in a standardized factory setting, and on-site hoisting can be completed in just half a day to a day, significantly shortening the construction period.

II. Disadvantages of Prefabricated Panel Roofs

1. Poor Waterproofing Performance:
   • The probability of leakage is high, with about 8 out of 10 households experiencing seepage, primarily due to improper panel joint treatment or aging of the waterproof layer.
   • Long-term water seepage can lead to steel bar corrosion and concrete cracking, further exacerbating structural damage.
2. Insufficient Insulation Performance:
   • The thickness of prefabricated panels is usually only 12 centimeters, resulting in poor heat insulation. Indoor temperatures are high in summer and weak in winter, requiring additional covering materials such as cinder and cement for improvement.
3. Low Earthquake Resistance:
   • The overall stiffness is weaker than that of cast-in-place structures. During earthquakes or uneven foundation settlement, cracks or displacements are prone to occur at panel joints, connections, and load-bearing walls.
4. Durability Controversy:
   • Although the designed service life is 50 years, some prefabricated panel houses built in the 1980s and 1990s may experience roof leakage and fine wall cracks within 30 years due to issues such as incomplete structural columns and lax panel end connections.
   • Professional safety assessments are required to classify them into grades (Grade A and B can be used normally, Grade C requires local reinforcement, and Grade D is treated as a dangerous building), rather than mandatory scrapping.
5. Joint Hazards:
   • Cracks are prone to occur at the joints between prefabricated panels, affecting structural stability and requiring regular inspection and repair.

III. Usage Recommendations

1. Prioritize Cast-in-Place Roofs When Economically Feasible: Although the cost is higher, their waterproofing, insulation, and earthquake resistance are significantly better than those of prefabricated panels.
2. If Insisting on Using Prefabricated Panels:
   • Strengthen waterproofing treatment by using high-quality waterproof materials and regular maintenance;
   • Avoid using them in earthquake-prone areas or areas with unstable foundations;
   • Regularly inspect panel joints and roof conditions, and promptly repair cracks.