Pingchao Prefabricated House Structure

Prefabricated houses in Pingchao's building structures have structural defects and aging risks, requiring classified disposal. For rural self-built houses, moisture prevention is necessary, and there are differences in construction efficiency, quality, and cost compared to brick-concrete houses.

Structural Characteristics and Safety Hazards

Prefabricated houses are assembled using factory-made concrete panels, with mostly simply-supported connections between panels, resulting in poor overall integrity and weak seismic performance (up to a maximum of 6 degrees, while cast-in-place houses can reach 8 degrees). Additionally, some exterior walls use flammable materials, leading to inadequate fire resistance. In the Wenchuan earthquake, 80% of the collapsed houses were prefabricated panel houses, highlighting their seismic deficiencies. Their lifespan is typically 30-50 years. After exceeding this service life, concrete carbonation and steel reinforcement corrosion occur, reducing load-bearing capacity and leading to issues such as wall cracking and floor deformation. Human-induced damage, such as unauthorized removal of load-bearing walls, further exacerbates risks.

Moisture Prevention for Rural Self-Built Houses

If prefabricated houses are used for rural self-construction, moisture prevention is crucial:

1. Laying Moisture Barrier Film: After backfilling the foundation, level it with fine sand and gravel, then cover it with high-density polyethylene film, and finally pour a concrete垫层 (sub-base). The drawback is limited durability, susceptibility to punctures, and reduced effectiveness in areas with high groundwater levels.
2. Creating a Prefabricated Panel Suspended Floor: After pouring the ground beams, backfill the soil to a height of 30-50 cm from the ground level, compact it, and then lay prefabricated panels to dissipate moisture through the cavity. Note that the backfilled soil must be compacted to avoid settlement.

Policies and Disposal Directions

The country adopts a strategy of "demolishing when necessary and renovating when possible":

• Priority Demolition: D-grade dilapidated houses, houses in key urban planning areas, and houses over 25 years old with low renovation value.
• Comprehensive Renovation: For structurally safe but functionally outdated houses, measures such as floor reinforcement, pipeline updates, and elevator installations are carried out, with government subsidies ranging from 70%-90%.
  Relocation methods include original-site reconstruction and relocation with area incentives (10%-20% additional area) and housing voucher relocation (compensation 20% higher than monetary compensation, with叠加 (stackable) subsidies).

Differences from Traditional Brick-Concrete Houses

1. Construction Efficiency: The main structure of a prefabricated house can be completed in as fast as 5 days, with fine decoration delivered within 2 months; a brick-concrete house takes 6-8 months.
2. Quality and Standardization: Components of prefabricated houses are factory-produced with millimeter-level errors; brick-concrete houses rely on the craftsmanship of workers, resulting in significant quality variations.
3. Seismic Performance: Modern prefabricated concrete or steel structures can achieve a seismic fortification intensity of 8 degrees, with steel structures improving seismic performance by over 50% compared to brick-concrete structures.
4. Cost and Flexibility: Prefabricated houses have an initial construction cost 10%-30% higher but lower lifecycle costs; their floor plans are fixed, making renovations difficult; brick-concrete houses offer greater flexibility for adjustments.