Conversion of Flat Roof to Prefabricated Panels

The decision to convert a flat roof to prefabricated panels requires careful consideration of the pros and cons, as its suitability depends on budget, regional conditions, and functional requirements.

Key Advantages of Prefabricated Panels

1. Low Cost: Prefabricated panels are significantly cheaper than cast-in-place concrete and have a shorter construction period (usually half a day to a day for hoisting and installation), making them suitable for scenarios with limited budgets and urgent completion needs.
2. Convenient Construction: Prefabricated panels are produced in factories to standardized specifications and only require hoisting and assembly on-site, imposing lower technical requirements on the construction team and saving labor costs.

Significant Drawbacks of Prefabricated Panels

1. Poor Waterproof Performance:
   • There are gaps of 2-3 centimeters between panels. Even if filled with cement or asphalt, these gaps are prone to cracking due to long-term thermal expansion and contraction, leading to leakage. In rural self-built houses, the leakage rate of prefabricated panel roofs is relatively high, necessitating regular maintenance (such as re-filling gaps or applying waterproof coatings), which increases long-term costs.
2. Insufficient Earthquake Resistance:
   • Prefabricated panels are independent components without an overall connecting structure. They have thin steel reinforcement and lack transverse tie bars, resulting in significantly lower load-bearing and earthquake resistance capabilities compared to cast-in-place concrete. In earthquake-prone areas, prefabricated panel roofs are prone to fracture or displacement due to vibrations, posing safety hazards, and are therefore not suitable for such regions.
3. Weak Thermal Insulation:
   • Most prefabricated panels are 12 centimeters thick and hollow, providing poor thermal insulation in summer (indoor temperatures rise easily) and weak heat preservation in winter (heat loss is rapid). Additional materials such as cinder, lime, or insulation boards are usually required to compensate, further increasing costs and construction complexity.
4. Lower Durability:
   • After long-term use, prefabricated panels are prone to elastic deformation (such as slight sagging) due to loads or environmental factors, with a lower safety factor than cast-in-place structures. If the foundation settles unevenly, the gaps between panels may widen, exacerbating leakage and structural risks.

Suitable Scenarios and Recommendations

• Recommended Use: If the budget is limited, the area is not earthquake-prone, and the requirements for waterproofing and thermal insulation are not high (such as for temporary housing or short-term occupancy), prefabricated panels can be considered, but the later maintenance costs must be accepted.
• Priority Given to Cast-in-Place Concrete: If conditions permit, cast-in-place concrete roofs are significantly superior to prefabricated panels in terms of integrity, durability, leakage prevention, and earthquake resistance. Although the cost is more than three times that of prefabricated panels, the long-term maintenance cost is low, making them more suitable for long-term occupancy or high-standard buildings.

Summary: Prefabricated panel roofs are an option for low-cost and rapid construction, but their drawbacks in terms of waterproofing, earthquake resistance, and thermal insulation must be weighed. If safety and durability are pursued, cast-in-place concrete is a better solution.