Structural Safety of Prefabricated Houses

The structural safety of prefabricated houses needs to be comprehensively evaluated from multiple aspects, including seismic performance, structural integrity, component conditions, usage and modification situations, assessment standards, and maintenance and reinforcement measures.

Seismic Performance: Prefabricated panel houses generally have poor seismic performance and insufficient integrity, making them prone to collapse during earthquakes. Many prefabricated panel houses built in the 1980s and 1990s did not consider seismic design, posing a higher risk in earthquake-prone areas. For example, in the 2008 Wenchuan earthquake, 90% of the collapsed houses were of prefabricated panel structures.

Structural Integrity:

• Foundation: Check for obvious settlement marks around the house, differences in height between indoor and outdoor floors, and diagonal cracks at the bottom of walls caused by uneven foundation settlement.
• House Tilt: Visually inspect whether the house shows any noticeable tilt or distortion.

Component Conditions:

• Prefabricated Floor Panels: Check for horizontal through-cracks at the bottom of the panels, obvious cracking at the joints between panels, signs of downward bending or sinking in the middle of the panels, and whether the concrete at the ends of the panels resting on the walls is loose, crumbling, or if the steel reinforcement is exposed and rusted.
• Load-Bearing Walls: Examine load-bearing walls for vertical or diagonal cracks, cracking and downward deformation at the lintels above door and window openings, severe weathering, spalling, or loosening of bricks or masonry at the base of the ground floor walls, and determine whether ring beams and structural columns were installed during construction (for three-story or higher brick-concrete prefabricated panel houses, the absence of these significantly reduces overall seismic resistance and safety).
• Node Connections: Pay attention to whether the support of the prefabricated panels on the walls is secure and free from loosening (the standard requires that the support length of prefabricated panels on brick walls should not be less than 80mm), and check for separation or cracks at the corners and intersections of walls.

Usage and Modification Situations: Verify whether there have been any unauthorized actions during the house's usage, such as removing load-bearing walls, creating or enlarging door and window openings in load-bearing walls; check for unauthorized additions of floors on the roof, installation of mezzanines, or stacking of excessively heavy items on the floor panels; if a house originally designed as a residence has been converted into a densely populated business premises, the significant increase in live load can also easily lead to safety incidents.

Assessment Standards: According to the "Comprehensive Safety Assessment Standard for Building Structures" (db11/t 637 - 2024), professional assessments can be conducted on prefabricated panel houses to determine their safety ratings.

Maintenance and Reinforcement: If safety hazards are found in prefabricated panel houses, timely maintenance and reinforcement should be carried out. For example, if cracks exceed standards, measures such as adding ring beams, applying carbon fiber sheets, or installing steel beams beneath the floor panels can be taken. The government also provides subsidy policies for eligible dangerous house renovations.