Flat Roof with Prefabricated Floor Slabs

The use of prefabricated floor slabs on flat roofs is relatively common in rural self-built houses, but there are deficiencies in waterproofing, earthquake resistance, thermal insulation, and attention needs to be paid to safety and maintenance requirements.

I. Advantages of Prefabricated Floor Slabs Prefabricated floor slabs were once widely used in rural self-built houses, mainly due to their low cost and fast construction speed. Lifting and installation can usually be completed in a day or half a day, making them suitable for scenarios with short construction periods and limited budgets. This construction method provided a feasible solution for quickly meeting housing demands in the past when technological conditions were limited.

II. Disadvantages of Prefabricated Floor Slabs

1. Prominent Waterproofing Issues: Prefabricated floor slabs are composed of multiple panels joined together. Cracks can easily occur at the joints due to material shrinkage, settlement, or construction errors. Even if waterproof coatings or membranes are used for treatment, long-term use may still result in leakage due to aging or structural deformation, with a relatively high probability of rainwater leakage.
2. Poor Earthquake Resistance: The connections between prefabricated floor slabs and walls are mostly rigid joints, resulting in insufficient integrity. Under earthquake action, dislocation or even fracture can easily occur at the joints, increasing the risk of building collapse. Therefore, their use is not recommended in earthquake-prone areas.
3. Poor Thermal Insulation Performance: The thickness of prefabricated floor slabs is usually around 12 centimeters, and heat conduction is relatively fast, making the indoor environment stuffy in summer and cold in winter. Additional insulation layers (such as foam boards or perlite) or secondary roofing materials (such as tiles or color steel plates) need to be laid to improve performance, but this will increase costs and construction complexity.

III. Policy and Maintenance Recommendations According to the "15th Five-Year Plan for Urban Renewal", prefabricated slab buildings need to determine disposal paths through safety appraisals:

• Grade A/B Buildings: They can participate in old residential community renovations, with a focus on repairing structural defects and improving waterproofing and thermal insulation performance.
• Grade C Dilapidated Buildings: They need to be repaired and reinforced, such as by adding structural columns and ring beams or replacing them with cast-in-place floor slabs to enhance integrity and earthquake resistance.

Daily maintenance requires regular inspection of joint sealing, timely repair of cracks; clearing snow from the roof before winter to avoid local overloading; and a comprehensive inspection of structural damage after earthquakes. If the building is located in an earthquake zone or is planned for long-term use, it is recommended to gradually transform it into a cast-in-place floor slab system to improve safety and durability.