Renovation of Prefabricated Slab Houses: Cast-in-Place Refurbishment

Under the policy environment of 2026, the renovation of prefabricated slab houses has shifted towards in-situ reconstruction as the primary approach, while cast-in-place refurbishment is gradually being phased out due to technical limitations and cost issues. Only localized leakage problems can be addressed using standardized waterproof refurbishment solutions. Detailed analysis is as follows:

I. Limitations of Traditional Cast-in-Place Refurbishment

Prefabricated slab houses, due to their spliced structure, have inherent gaps that are prone to causing leakage, substrate damage, and dynamic deformation issues. Traditional refurbishment methods, such as treating only slab joints or surface waterproof layers, fail to address structural defects fundamentally, resulting in a high recurrence rate of leakage. For instance, the Phase I project of Zhonghuan Jiayuan in Putuo District, Shanghai, suffered from severe roof leakage and ultimately resolved localized issues through a systematic waterproof refurbishment plan (including substrate repair, slab joint reinforcement, and national standard membrane waterproofing), but did not involve overall structural renovation. Such solutions can only alleviate surface problems, and their long-term effectiveness is influenced by factors such as material aging and structural deformation, making it difficult to completely eliminate hidden dangers.

II. Policy Shift in 2026: In-Situ Reconstruction Replacing Cast-in-Place Refurbishment

The 2026 urban renewal policy explicitly prohibits the approval of pure aesthetic renovation projects, such as exterior wall beautification, for C- and D-grade dilapidated houses (e.g., prefabricated slab buildings over 38 years old with foundation settlement and high structural risks), and requires classified disposal:

• Elimination of 'cosmetic projects': The policy emphasizes prioritizing structural safety and prohibits concealing hidden dangers through superficial refurbishment;
• Promotion of in-situ reconstruction: For eligible buildings, demolition and reconstruction are promoted instead of cast-in-place reinforcement. This is because the inherent defects of prefabricated slab structures (such as the lack of integral steel reinforcement pouring and low seismic resistance) are difficult to repair through subsequent measures, and the cost of reinforcement may approach 70% of the reconstruction cost.

III. Technical Challenges of Cast-in-Place Refurbishment

If cast-in-place refurbishment is forcibly implemented, the following technical bottlenecks need to be overcome:

• Structural adaptability: The combination of prefabricated slabs and cast-in-place layers requires addressing splicing gaps to prevent cracking due to thermal expansion and contraction;
• Load limitations: The foundation bearing capacity of old prefabricated slab buildings is limited and may not be able to withstand the additional weight of the cast-in-place layer, requiring prior reinforcement;
• Cost-benefit imbalance: Cast-in-place refurbishment requires significant investment in structural inspection, foundation reinforcement, and construction, with the overall cost potentially exceeding that of in-situ reconstruction.

IV. Alternative Solutions and Applicable Scenarios

• Localized leakage treatment: Reference can be made to the standardized waterproof refurbishment process (such as substrate repair, slab joint reinforcement, and membrane waterproofing), but regular maintenance and assessment of long-term effectiveness are required;
• Resolution of structural defects: The 2026 policy more strongly recommends in-situ reconstruction, which systematically eliminates safety hazards through complete demolition and repouring.