Renovation of Old Houses with Prefabricated Panels

The renovation of old houses with prefabricated panels requires a comprehensive assessment of structural safety, combined with standardized construction and careful consideration of potential issues.

Structural Safety Assessment Before Renovation

The structural team needs to conduct a comprehensive inspection of the old house, focusing on the crack width of the prefabricated panels. Special treatment is required if the crack width exceeds 0.3 millimeters. At the same time, the connection status between the prefabricated panels and the ring beams should be checked, and bolts with a rust rate exceeding 30% need to be replaced. In addition, the overall stability of the house should be evaluated, such as whether there is wall inclination or foundation settlement, to provide a scientific basis for subsequent renovation.

Key Construction Measures During Renovation

1. Roof Renovation: After removing the original wooden roof, a new concrete roof is poured while maintaining the original height to enhance waterproof performance and structural stability, and to provide a foundation for subsequent laying of various roofing materials (such as tiles and metal sheets).
2. Exterior Wall Treatment: After removing all the exterior wall tiles, repainting and rebar-planting and grouting are carried out. Rebar-planting can strengthen the load-bearing capacity of the walls, while grouting improves the tensile performance and prevents wall cracking or peeling.
3. Temporary Support System: Before construction, temporary supports need to be erected. Steel pipe supports are set up every 1.2 meters along the length of the prefabricated panels, and key nodes are replaced with H-shaped steel beams with a cross-section of no less than 200*200 millimeters to ensure structural safety during the demolition process.
4. Panel Joint Treatment: After removing the original filling materials, No. 6 threaded rebars are implanted and C30 fine aggregate concrete is poured to enhance the connection strength of the panel joints and reduce the risk of crack propagation.
5. Additional Constructional Columns: Constructional columns with a cross-section of 240*240 millimeters are added at the four corners of the house, combined with No. 6 and No. 8 rebars tied together and connected to the floor slab to improve the overall seismic performance.

Construction Sequence and Standard Requirements

The renovation should follow the principle of segmented demolition of "middle first, then sides", maintaining symmetrical demolition, with a daily demolition volume not exceeding 30% of the total floor area. During the demolition process, the stress changes of the support system should be monitored in real-time, and the use of heavy hammers for impact demolition is prohibited to avoid impacting the foundation structure.

Controversies and Limitations of Renovation

Although renovation can improve safety, prefabricated panel houses have problems such as poor thermal insulation and sound insulation effects and a short design life (usually 40 years). Some houses have already "exceeded their service life", showing wall peeling, wall cracks, and even becoming dangerous houses. In addition, in 2023, relevant departments clearly stipulated that the construction of prefabricated panel houses and other buildings that do not meet safety standards is prohibited from being newly built, renovated, or expanded within the scope of urban construction land, which further limits the long-term value of renovation.