Waterproofing of Prefabricated Panels on Old House Roofs

Waterproofing of prefabricated panels on old house roofs requires a systematic renovation approach, addressing structural characteristics and leakage challenges comprehensively. Specific measures are as follows:

1. Comprehensive Roof Clearance and Precision Repair of Substrate Defects Prefabricated panel roofs, exposed to natural elements for extended periods, often develop surface irregularities, sanding, peeling, and fine honeycomb cracks. Loose and aged substrates create hidden pathways for water infiltration. It is essential to thoroughly remove debris, dust, and failed waterproofing layers from the roof surface. High-pressure grouting repairs or epoxy mortar filling should be applied to substrate cracks and holes, ensuring a flat, dense substrate and eliminating initial routes for rainwater penetration.

2. Rigid Filling and Anti-Displacement Treatment of Panel Joints The joints between prefabricated panels are primary channels for leakage, continuously opening and closing due to temperature variations and settlement. Traditional waterproofing materials are prone to cracking under tension. High-strength polymer mortar or specialized joint sealants should be used for rigid filling of panel joints, forming the first line of waterproofing defense. After filling, a weather-resistant mesh fabric should be laid over the joint surface to enhance tensile resistance and prevent cracking of the filling layer due to structural deformation.

3. Full-Coverage Waterproofing with National Standard Thickened Membranes and Multi-Layer Protection Ordinary thin waterproof coatings lack sufficient deformation resistance. National standard thickened SBS/APP modified bitumen membranes or TPO polymer membranes should be selected for full-roof installation using hot-melt or mechanical fastening methods. The membrane thickness should be no less than 4mm, with an overlap width of ≥10cm, creating a continuous, dense waterproof layer. For roof corners, protrusions, and other critical nodes, additional membrane layers should be added to reinforce local protection.

4. Specialized Exposed Waterproofing System for Gutters Gutters are areas most severely exposed to water accumulation and UV radiation, where conventional waterproofing materials are prone to premature aging and failure. Weather-resistant silicone sealants or acrylic waterproof coatings, combined with weather-resistant reinforcing fiber fabrics, should be applied in multiple coats to form an elastic waterproof layer. Simultaneously, gutter debris should be cleared, and drainage slopes repaired to ensure rapid water discharge and reduce long-term erosion of the waterproof layer by standing water.

5. Abandon Local Repairs, Adopt Systematic Renovation Logic Leakage in prefabricated panel roofs is characterized by concealment and persistence, making local repairs ineffective in addressing hidden water migration. A five-step approach of 'clearance-repair-filling-waterproofing-reinforcement' should be employed to construct a complete waterproofing system from substrate to surface, enhancing overall water resistance of the roof and reducing the risk of recurrent leakage.