Inspection Standards for Prefabricated Houses

The inspection standards for prefabricated houses cover structural integrity, component conditions, usage and modification situations, and safety classification, as detailed below:

I. Structural Integrity and Foundation Inspection

Foundation: Inspect for signs of ground settlement around the house, differences in indoor and outdoor ground levels, and diagonal cracks at the base of walls. If the foundation settlement rate exceeds 2mm per month for two consecutive months without signs of stopping, or if the settlement difference between adjacent houses exceeds the standard, caution is advised. Cracks, crumbling, steel reinforcement corrosion in concrete foundations, or vertical cracks in brick foundations indicate a decrease in load-bearing capacity. House Tilt: Visually inspect for any noticeable tilt or distortion of the overall structure.

II. Specialized Inspection of Core Components

1. Prefabricated Floor Slabs:
   • Bottom Cracks: Observe the ceiling for horizontal through-cracks or joint cracks; through-cracks can severely affect load-bearing capacity.
   • Deflection: Check for significant sagging in the middle of the floor slab.
   • End Damage: Confirm whether the concrete at the ends of the prefabricated slabs is loose, crumbling, or if the steel reinforcement is corroded.
2. Load-Bearing Walls:
   • Stress Cracks: Focus on checking for vertical, diagonal cracks, or deformation and cracking of door and window lintels. Cracks wider than 3mm or a wall tilt rate exceeding 0.7% require caution.
   • Wall Weathering: Inspect the bottom layer of wall roots for severe weathering or spalling of bricks, which weakens the effective cross-section.
   • Structural Measures: For brick-concrete prefabricated slab houses of three stories or more, the absence of ring beams and constructional columns significantly reduces earthquake resistance. Weakened connections between vertical and horizontal walls or cracked ring beams can reduce overall stability.
3. Beams and Columns: Beams with vertical, horizontal, or diagonal cracks (wider than 0.3mm) or horizontal cracks at the bottom of beams, as well as cracks, spalling, or decay in columns, all affect load-bearing capacity.
4. Roof Trusses: Rotted or insect-infested wooden truss members or loose joints, as well as deformed, corroded, or loosely connected steel truss members, reduce load-bearing capacity.
5. Node Connections:
   • Lap Length: The support length of prefabricated slabs on brick walls should be no less than 80mm.
   • Tie Conditions: Check for separation or cracks at wall corners and junctions.

III. Inspection for Unauthorized Modifications and Usage Environment

Verify whether there has been removal or modification of load-bearing walls, unauthorized additions (increased loads) (such as adding floors on rooftops or stacking heavy objects on floor slabs), or changes in usage (such as converting residential spaces into crowded venues), as these actions significantly increase safety risks.

IV. Classification of House Safety Appraisal

Professional institutions classify the safety level according to the "Standards for Dangerous House Appraisal" (JGJ 125-2016):

• Grade A: No dangerous components; structurally safe.
• Grade B: Individual components are dangerous but do 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 house is dangerous.