What is the Prefabricated Floor Slab for Houses?
The prefabricated floor slab for houses is a commonly used floor component in early 20th-century architecture. It is an engineered module or panel that is produced and processed in a prefabrication yard and then transported to the site for installation.
Production and Historical Application of Prefabricated Slabs
Prefabricated slabs are concrete components produced through specific processes in a prefabrication yard. Workers first build a hollow mold using wood, insert steel bars as the framework, pour in cement, let it dry, and finally remove the mold. These components are named for their ability to be produced in advance and quickly installed on-site. From the 1960s to the 1990s, due to a surge in housing demand, prefabricated slabs were widely used because of their low cost and fast construction speed. Approximately 200 million square meters of prefabricated slab houses were built nationwide, covering 12 million households.
Defects of Prefabricated Slab Houses
Prefabricated slab houses have significant limitations:
- Short lifespan: The designed lifespan is generally 30-50 years. After aging, the structural strength declines, and debris may fall off.
- Poor earthquake resistance: The overall integrity is weak, and joints are prone to breakage and collapse during earthquakes, posing safety hazards.
- Waterproofing issues: Joints between panels are prone to water seepage, leading to damp interiors or wall damage.
Current Handling Policies (2025 New Regulations)
Prefabricated slab houses are not subject to comprehensive demolition but are handled through classification:
- Scope of demolition:
- Dangerous houses at the prefecture level: Such as those with foundation subsidence exceeding 5 cm, wall cracks wide enough to insert a coin, or earthquake resistance below 70% of current standards.
- Houses conflicting with planning: "Nail houses" located on planned land for subways, schools, etc.
- Houses with high maintenance costs: Those over 25 years old with maintenance costs exceeding the cost of demolition and reconstruction.
- Renovation as the priority: Approximately 80% of prefabricated slab houses are improved in terms of safety and living quality through renovation rather than direct demolition.
Renovation Methods and Standards
Renovation plans are formulated based on housing safety appraisal reports (graded A, B, C, and D):
- A/B-grade houses: The main structure is safe. Renovations include repairing roofs, replacing pipes, upgrading fire safety facilities, and installing elevators as part of old residential area improvements.
- C-grade houses: Partially dilapidated but repairable. Earthquake resistance is enhanced by reinforcing walls, beams, columns, floors, and foundations.
- D-grade houses: Overall dilapidated and without repair value. Demolition is carried out only when they meet expropriation conditions (e.g., for road construction or public facilities) in accordance with the law.
The handling of prefabricated slab houses reflects the principle of "safety first and classified strategies," ensuring resident safety while avoiding resource waste and promoting refined urban renewal.
