Prefabricated Floor Slab for House Mezzanine

The use of prefabricated floor slabs for house mezzanines requires a comprehensive assessment of their suitability, with priority given to adhering to current regulations and considering safety upgrades.

1. Basic Characteristics and Historical Applications of Prefabricated Slabs

Prefabricated slabs, widely used in the early 20th century as floor forms, are engineering modules prefabricated in factories and transported to the site for installation. Their manufacturing process involves nailing wooden planks to create hollow molds, laying out steel reinforcement, pouring cement, and then removing the wooden planks after drying to form the finished product. Depending on their structure, prefabricated slabs are classified into solid and hollow types. The hollow structure achieves lightweighting by reducing non-load-bearing concrete and was once widely used in scenarios such as floor slabs and roof insulation layers.

2. Limitations of Existing Prefabricated Slab Houses

Existing prefabricated slab houses generally have the following issues:

1. Weak Earthquake Resistance: Prefabricated slabs are assembled in blocks, resulting in poor integrity and susceptibility to dislocation or collapse during earthquakes.
2. Poor Sound and Heat Insulation Performance: Hollow structures or material aging lead to a significant decline in heat and sound insulation effects.
3. Limited Design Lifespan: Most prefabricated slab houses are designed for a lifespan of 30-50 years, with some buildings already exceeding this period, posing safety risks.
   Since 2022, China has implemented renovation policies focusing on repairing and upgrading prefabricated slab houses, with demolition only for buildings that meet the criteria for dangerous structures. During renovation, it is essential to reinforce structural connection points and improve heat and sound insulation performance.

3. Key Considerations for Using Prefabricated Slabs in Mezzanines

1. Load-Bearing Limits:
   • The live load ratings for prefabricated slabs in ordinary residential buildings are classified as Grade I (1 kN/m²) and Grade II (2 kN/m²), with a minimum requirement of Grade IV (4 kN/m²) specified in the southwest region.
   • It is necessary to calculate the load based on the intended use of the mezzanine (e.g., storage or living) to avoid structural damage caused by overloading.
2. Slab Joint Specifications:
   • Slab joints less than 30 mm are considered unqualified, 30-50 mm are acceptable, 50-110 mm require reinforcement, and those exceeding 110 mm but less than 500 mm must be made into slab bands.
   • Improper handling of slab joints can easily lead to cracks and water leakage, necessitating strict adherence to specifications during construction.

4. Alternative Solutions in Modern Construction Technology

Current construction technology has shifted towards cast-in-place concrete and prefabricated buildings:

1. Cast-in-Place Concrete: Offers good integrity and strong earthquake resistance but has a longer construction period.
2. Prefabricated Buildings: Enhance earthquake resistance through modular factory-prefabricated components, reducing the construction period by 30% and aligning with green building trends.
   If considering mezzanine renovation, it is recommended to evaluate the suitability of prefabricated slabs in accordance with current regulations or prioritize the use of cast-in-place structures or prefabricated technology to enhance safety and durability.