Load-Bearing Walls in Old Prefabricated Panel Houses

Identifying load-bearing walls in old prefabricated panel houses requires a comprehensive assessment based on structural location, material, drawings, and thickness. During renovation, it is essential to strictly adhere to safety regulations to avoid compromising structural stability.

Identification Methods

1. Structural Location: Load-bearing walls are typically located in the central area of the house, perpendicular to the beams, forming the main load-bearing framework. If a wall is directly connected to beams and floor slabs and lies along the house's primary load-bearing path, it should be prioritized for inspection.
2. Material Identification:
   • Tapping Test: Gently tap the wall with a hard object. Load-bearing walls, due to their solid structure, will produce a dull sound, while non-load-bearing walls (such as lightweight partition walls) will have a hollow echo.
   • Slot Observation: If the wall contains steel reinforcement mesh or a concrete layer (which requires professional equipment for detection), it can be identified as a load-bearing structure. Note that the depth of the slot should be controlled (recommended ≤50mm) to avoid damaging the structure.
3. Comparison with Architectural Drawings: In the original construction drawings, walls marked in black are generally load-bearing walls. However, drawings for old houses may be missing, necessitating verification through other methods.
4. Thickness Assessment: Load-bearing walls often use 240mm thick solid brick walls or cast-in-place concrete (thickness ≥200mm). Walls with a thickness ≥20cm are usually load-bearing, while those around 10cm are mostly lightweight partition walls.

Professional Inspection Techniques

1. Instrument Inspection: Using equipment such as steel reinforcement scanners and infrared thermal imagers allows for non-destructive detection of the internal distribution of steel reinforcement and the density of concrete within the walls.
2. Load Calculation: Stress analysis software can simulate the forces acting on the house to determine the location and load-bearing capacity of load-bearing walls.
3. Third-Party Appraisal: Commission a professional institution to conduct a specialized assessment, comparing the structural layout with similar house types in a case database to issue an authoritative report.

Renovation Precautions

1. Prohibited Actions:
   • If the opening area in a load-bearing wall exceeds 1/10 of the wall's area, reinforcement is required; horizontal cutting deeper than 50mm must be reinforced with steel bonding.
   • It is strictly prohibited to create openings for doors and windows in load-bearing walls. Openings with a thickness exceeding 1/3 of the wall or single-point suspensions weighing more than 5kg are considered high-risk operations.
   • Lightweight partition walls beneath beams are often load-bearing lightweight walls; their removal can lead to beam cracking and floor slab subsidence.
   • In brick-and-concrete structures, damaging solid brick walls thicker than 24cm can weaken earthquake resistance; creating large openings in prefabricated panel walls may cause the entire panel to become unstable and detach.
2. Alternative Solutions: When partial wall removal is necessary, the load can be transferred by adding steel trusses to ensure structural safety.

Other Considerations

1. Misjudgment Risks: Joints between prefabricated panels can be easily mistaken for wall cracks and should be tested with epoxy resin injection. Buildings constructed before the 1980s may use hollow bricks to impersonate load-bearing walls, requiring drilling for sample verification (hole diameter ≤8mm).
2. Regional Differences: Prefabricated panel houses in northern regions often use red brick load-bearing walls (with high frost resistance), while those in southern regions commonly feature concrete hollow block walls (requiring density testing of the filling). It is recommended to use two verification methods before construction and contact a professional institution for re-evaluation if necessary.
3. Old House Risks: Approximately 41.7% of brick-and-concrete houses over 30 years old exhibit diagonal cracks in load-bearing walls or widening of corner cracks in window openings. If cracks wider than 3mm are left unaddressed, the risk of excessive floor slab deflection increases sharply within 18 months, necessitating immediate structural inspection.