Prefabricated Two-Story House

It is entirely feasible to use prefabricated slabs for the ground floor and cast-in-place concrete for the second floor of a prefabricated house. The following analysis covers technical feasibility, structural characteristics, and the possibility of demolition:

I. Technical Feasibility
In rural self-built houses, the combination of using prefabricated slabs for the ground floor and cast-in-place concrete for the second floor is a common practice. Prefabricated slabs are laid individually to complete the flooring of the first floor, offering fast construction speed and lower costs. The second-floor cast-in-place concrete roof is poured as a whole with reinforced concrete, forming a rigid connection with the upper and lower structures. This layered construction method leverages the economic benefits of prefabricated slabs while compensating for their lack of integrity through the cast-in-place concrete roof, making it technically entirely feasible.

II. Comparison of Structural Characteristics

1. Prefabricated Slabs

   • Connection Method: Prefabricated slabs are independent components placed on walls for load-bearing, with no rigid connection to the walls, preventing the house from forming an integral structure.
   • Performance Defects:
     • Stability Risks: Poor earthquake resistance, prone to displacement or fracture under seismic or external impacts.
     • Waterproofing Issues: Cracks can easily form at slab joints due to settlement or thermal expansion and contraction, leading to water leakage.
     • Lifespan Limitation: Designed lifespan of about 50 years, with thinner steel bars and a lower safety factor compared to cast-in-place structures.

2. Cast-in-Place Concrete Roof

   • Integrity: Reinforced steel bars and concrete are poured together, forming a rigid connection with walls, beams, and columns, making the house an integral structure.
   • Performance Advantages:
     • Earthquake Resistance: Stress is dispersed through the steel bar framework, significantly outperforming prefabricated slabs in earthquake resistance.
     • Waterproofing: No joints, effectively preventing leakage when combined with a waterproof layer.
     • Durability: Concrete encases steel bars to prevent rusting, with a designed lifespan of over 70 years.

III. Analysis of Demolition Possibility
Whether a prefabricated slab two-story house should be demolished requires comprehensive assessment:

1. Situations Requiring Demolition:

   • Safety Hazards: If severe cracks, steel bar corrosion, or house tilting occur in the prefabricated slabs, demolition and reconstruction are necessary.
   • Planning Requirements: During urban renewal or rural centralized planning, demolition may be required by policy.
   • Renovation Needs: Homeowners may actively choose demolition to improve living quality (e.g., adding floors or expanding).

2. Situations Allowing Retention:

   • Structural Safety: If the prefabricated slabs show no significant damage and the house settlement is stable, they can continue to be used after reinforcement (e.g., adding ring beams).
   • Planning Delay: If not included in the near-term demolition plan, demolition can be postponed.
   • Economic Factors: When the cost of demolition and reconstruction is too high, local repairs can extend the service life.

Conclusion: The combination of prefabricated slabs for the ground floor and cast-in-place concrete for the second floor is reasonable and safe for rural house construction. However, regular inspections of the prefabricated slabs are necessary. If the house meets safety standards and has no renovation needs, there is no need to demolish it due to the presence of prefabricated slabs. If structural risks or planning requirements exist, timely action should be taken.