Prefabricated Slab Building Structure

Prefabricated slab buildings are houses constructed primarily using prefabricated slabs, with their structural characteristics, uses, and advantages and disadvantages as follows:

Structural Composition and Types

Prefabricated slabs are cement components manufactured in factories. During production, wooden molds are nailed together, steel bars are arranged, and cement is poured to form the slabs, which come in two types: solid and hollow. The hollow structure achieves lightweighting by reducing the concrete in non-load-bearing parts, lowering the overall weight. The dimensions of prefabricated slabs are clearly specified: for residential use, the maximum span is 4.2 meters, the width is mainly 500mm and 600mm, and the common thicknesses are 120mm and 150mm; the length is designed according to a 300mm modulus (e.g., 3000mm, 3300mm), with the longest ordinary slab being 4200mm and the width mostly being four-hole 400mm or five-hole 500mm.

Uses and Performance Standards

Prefabricated slabs are widely used in construction, mainly for floor slabs and roof insulation layers, among other scenarios. The live load capacity ratings vary depending on the use: for general residential use, Class I slabs can withstand 1kN/m², Class II slabs can withstand 2kN/m², and in the southwest region, the minimum specified is Class IV slabs (4kN/m²) to meet higher load requirements.

Defects and Limitations

1. Insufficient Seismic Performance: Although steel bars are added inside the prefabricated slabs, the overall connection method (e.g., at joints) has significantly lower seismic capacity compared to cast-in-place concrete structures, making them prone to fracture or displacement during earthquakes.
2. Poor Sound Insulation and Thermal Insulation: The hollow structure or thin slab design results in weak sound insulation performance, with neighbors' activities clearly audible; the thermal insulation performance is also inadequate, leading to stuffy interiors in summer and cold interiors in winter, requiring additional reliance on air conditioners or heating.
3. Difficulty in Structural Adjustment: As prefabricated components, the internal steel bar layouts of prefabricated slabs are fixed, and large-scale demolition or modification of walls or floor slabs is almost not allowed, limiting the flexibility of space renovation.
4. High Risk of Water Leakage: Over time, cement components are prone to cracks, and the gaps at joints increase, leading to rainwater leakage and requiring regular maintenance.
5. Short Service Life: The design life is about 30-50 years. Prefabricated slab houses built in the 1970s-1990s are approaching or have exceeded their service lives, with widespread aging phenomena (such as steel bar corrosion and concrete carbonation).

Modern Alternatives and Policy Orientation

With the development of construction technology, cast-in-place concrete and prefabricated buildings are gradually replacing traditional prefabricated slab houses. Since 2022, China has implemented a policy of renovating old buildings, focusing mainly on repairing and renovating prefabricated slab houses (such as strengthening structures and improving thermal insulation) and only demolishing buildings that have reached the dangerous building standard to balance safety needs with resource utilization.