Water Leakage in Prefabricated Panel Houses in Shanghai

Water leakage issues in prefabricated panel houses in Shanghai are relatively common, primarily due to structural defects and climatic influences, necessitating systematic renovation solutions.

Core Causes of Water Leakage

1. Defects in the Jointed Structure
   The roofs of prefabricated panel houses are composed of multiple independent concrete panels joined together, with the panel joints serving as continuous channels. Affected by temperature-induced expansion and contraction, building settlement, and roof loads, the panel joints continuously open and close, causing ordinary waterproof layers to be torn and delaminated, and forming persistent water seepage channels. For example, in Unit 1102 of Building 72 in Phase I of Zhonghuan Jiayuan in Putuo District, the entire roof leaked due to panel joint issues.

2. Substrate Damage and Hidden Water Migration
   The surfaces of prefabricated panels are prone to unevenness, sanding, peeling, and fine cracks, leading to loose and aged substrates after prolonged water immersion. Rainwater freely migrates beneath the waterproof layer through panel joints or substrate gaps, causing misalignment between the leakage points and the seepage locations. In a handling case in Changbai Xincun, Yangpu District, approximately 70% of the leakages were of the "panel joint water migration" type, with water flowing out of place within the prefabricated panel cavities.

3. Dynamic Deformation and Poor Adaptability of Waterproof Materials
   Seasonal temperature differences cause thermal expansion and contraction of the prefabricated panels, resulting in frequent dynamic displacement of the panel gaps. Ordinary thin waterproof coatings or non-standard membranes lack sufficient tensile and deformation resistance, easily cracking and failing in the short term, with a much higher re-leakage rate compared to cast-in-place roofs.

4. High-Risk Areas at Pipe Penetrations
   Prefabricated panels require pre-reserved or on-site drilled holes for pipe installations. The gaps between the pipes and the floor slabs are originally filled with mortar or fine aggregate concrete, but due to differences in thermal expansion coefficients of the materials, they are prone to cracking after long-term use. The areas around toilet drain pipes and floor drain pipes in bathrooms are high-risk zones for water leakage.

5. 叠加影响 of Shanghai's Special Climate
   Large temperature differences between winter and summer exacerbate the expansion of cracks in the panel joint mortar layers; the high humidity during the plum rain season accelerates substrate aging; and extreme weather events such as heavy rain pose significant challenges to the waterproofing system. For example, on September 13, 2025, heavy rain in Shanghai caused collective leakage in 28 households of prefabricated panel houses at 7943 Shangnan Road.

Solutions

Shanghai Ruisheng Construction Engineering Co., Ltd. has introduced a systematic renovation solution:

• Comprehensive Obstacle Removal and Substrate Repair: Remove the original ineffective waterproof layers and finely repair substrate damage;
• Rigid Infill and Reinforcement of Panel Joints: Use high-strength materials to fill the panel joints, enhancing structural stability;
• Full-Domain Protection with National Standard Thickened Membranes: Use genuine Oriental Yuhong waterproofing materials to cover the entire roof;
• Specialized Exposed Waterproofing Reinforcement for Gutters: Strengthen waterproofing in areas prone to water accumulation, such as gutters.
  The project provides a 5-year formal written warranty upon completion and acceptance, abandoning the traditional patchwork approach of local leak repairs.