Flat Roof Prefabricated Slab Paving

The use of prefabricated slabs for paving flat roofs was once a widely adopted construction method in rural self-built houses, characterized by low cost and fast construction. However, it has defects in waterproofing, insulation, and safety, necessitating a trade-off based on actual needs.

Structural and Installation Characteristics

Prefabricated slabs are molded in advance at factories or on-site using materials such as crushed stone, cement, sand, and steel bars (coiled or cold-drawn wires). They are then lifted and laid piece by piece onto roof supports using lifting equipment (e.g., cranes). The gaps between slabs are filled and connected with concrete or cement mortar to form an integrated structure. The core advantage lies in high construction efficiency: up to 40-50 square meters of lifting work can be completed in a single day, with relatively low total costs (e.g., approximately 800 yuan for a 40-50 square meter roof, including lifting expenses). This method was popular in rural areas 20 years ago due to its low technical threshold and easy access to materials.

Analysis of Core Defects

1. Poor Waterproofing Performance:

   • Prefabricated slabs are not integrally connected to walls, making seams prone to water infiltration.
   • Gap treatment between slabs relies on construction specifications; if not filled densely or if foundation settlement causes cracks, leakage worsens.
   • The technical proficiency of construction workers directly affects waterproofing results, with some projects requiring post-rainy season inspections to confirm quality. Statistics indicate an 80% probability of water leakage in prefabricated slab roofs.

2. Insufficient Insulation and Heat Resistance: The 12-centimeter-thick hollow prefabricated slabs have weak heat insulation properties, necessitating additional covering with materials like cinder or lime to enhance insulation. Otherwise, indoor temperatures soar in summer and heat dissipates rapidly in winter.

3. Low Earthquake Resistance: The non-integral structure results in a significantly lower seismic coefficient compared to cast-in-place roofs, posing safety risks in earthquake-prone areas and making it unsuitable for regions with high seismic intensity requirements.

4. Limited Durability: Over long-term use, foundation settlement or material aging (e.g., steel bar corrosion, concrete carbonation) can lead to slab cracking, requiring regular maintenance.

Improvement Recommendations

• Prioritize Cast-in-Place Roofs: If the budget allows, opt for cast-in-place concrete roofs, which offer strong integrity, excellent waterproofing, and seismic performance. Although initially more costly, long-term maintenance expenses are lower.
• Enhance Waterproofing of Prefabricated Slabs: Use high-quality waterproofing membranes (e.g., SBS modified asphalt membranes), ensure proper construction at slab seams and wall connections, and conduct regular inspections and maintenance.
• Short-Term Emergency Measures: Covering with temporary materials like plastic film can alleviate water leakage issues, but these have a lifespan of only 2-3 years and require timely replacement.

Summary: Prefabricated slab paving roofs are suitable for areas with limited budgets, high demands for construction speed, and stable geological conditions. However, their drawbacks in terms of water leakage, poor insulation, and safety must be accepted. Decisions should be based on a comprehensive consideration of economic conditions, house usage, and local geological conditions, with consultation from professional structural engineers when necessary.