Inspection Standards for Prefabricated Houses

The inspection standards for prefabricated houses primarily focus on structural safety, public facilities, and unauthorized modifications, and are classified into four grades (A, B, C, and D) according to the 'Standards for Dangerous Building Appraisal' (JGJ 125-2016).

I. Structural Safety Inspection

1. Foundation: Check for uneven settlement. If the settlement rate exceeds 2mm/month for two consecutive months without signs of stopping, or if adjacent buildings show significant settlement cracks with excessive settlement differences, caution is advised. Signs of reduced load-bearing capacity in the foundation include concrete cracks, crumbling, carbonation, exposed and corroded steel reinforcement, or numerous vertical cracks in brick foundations.
2. Superstructure:
   • Walls: Diagonal, horizontal, or cross cracks in load-bearing walls wider than 3mm, a tilt rate exceeding 0.7%, or effective cross-section reduction due to material weathering and spalling all affect stability.
   • Beams and Columns: Beam cracks exceeding specifications (e.g., a limit of 0.3mm for flexural members), horizontal cracks at the beam bottom, or diagonal cracks at the beam ends indicate insufficient load-bearing or shear capacity; column cracks, spalling, or decay reduce load-bearing capacity.
   • Slabs: Extensive cracks, especially penetrating cracks, or irregular long cracks in cast-in-place slabs and cracked or displaced joints in prefabricated slabs require attention.
   • Roof Trusses: Decay, insect damage, or loose joints in wooden truss members, and deformation, corrosion, or loose connections in steel truss members all reduce load-bearing capacity.
3. Structural Integrity: Weakened connections between longitudinal and transverse walls, fractured ring beams, and crumbling concrete in structural columns reduce overall building stability. Although such issues in Grade C dangerous buildings do not completely destroy the structure, they significantly impair collaborative working capacity.

II. Public Facility Inspection Although not structural issues, aging pipelines, failed waterproofing, and blocked fire exits directly affect living safety. For example, prefabricated buildings constructed in the 1980s or earlier often have water and electricity pipeline designs that cannot meet current usage intensities, leading to common issues such as water leaks, tripped circuit breakers, and blocked sewers.

III. Unauthorized Modification Inspection Verify whether the building has undergone unauthorized removal of load-bearing walls, the creation of door/window openings or enlargement of existing openings in load-bearing walls, the addition of floors or mezzanines on the roof, or the placement of heavy items (e.g., water tanks, equipment) on the floor slabs. If a residential building originally designed for private use is converted into a crowded public space (e.g., a restaurant or KTV), the substantial increase in live loads can easily lead to safety incidents.

IV. Building Grade Classification After a professional institution issues a report, the building is classified according to the standards:

• Grade A: No dangerous components; structurally safe.
• Grade B: Individual dangerous components; does not affect the main structure's safety.
• Grade C: Some load-bearing structures do not meet safety requirements; locally dangerous.
• Grade D: Load-bearing structures have failed; the entire building is dangerous.