How to Waterproof Prefabricated Panels on House Roofs

Waterproofing of prefabricated panels on house roofs requires a combination of moisture-proofing and leak-proofing, with an emphasis on holistic treatment to avoid water migration issues caused by localized waterproofing.

Moisture-Proofing Measures

1. Laying Moisture-Proof Membranes: Lay specialized moisture-proof membranes on the roof substrate surface to form a physical barrier layer, reducing moisture penetration into the interior through gaps in the prefabricated panels or capillary action. The moisture-proof membrane must be sealed at the junctions with the wall foundation to prevent moisture intrusion from the edges.
2. Reinforcing Wall Foundations: Inspect and reinforce the connection areas between the prefabricated panels and the walls to prevent cracks from forming due to structural loosening. If cracks have already appeared in the walls, repair the cracks and fill them with sealing materials before covering them with a moisture-proof membrane to prevent moisture diffusion through the cracks.
3. Improving Ventilation Conditions: Install additional ventilation facilities (such as ventilation ducts or exhaust fans) in underground vents or concealed areas of the roof to accelerate air circulation and reduce the risk of moisture accumulation. This is particularly suitable for houses in humid regions or low-lying areas.

Leak-Proofing Measures

1. Roof Coating Waterproofing:

   • Select flexible waterproof materials such as polyurethane coatings or acrylic coatings and apply them directly to the surface of the prefabricated panels to form a continuous waterproof layer. These materials have good elongation properties and can adapt to minor deformations of the prefabricated panels, making them suitable for small houses or localized repairs.
   • During construction, clean the substrate of dust and oil to ensure strong adhesion between the coating and the panel surface; apply at least two coats with a thickness of 1.5-2mm, overlapping them to enhance sealing.

2. Laying Waterproof Membranes:

   • Use thick materials such as SBS modified bitumen membranes or PVC membranes and lay them on the roof through hot melting or adhesive bonding to form a durable waterproof barrier. The seams of the membranes must be sealed with special adhesives and fixed under pressure to prevent leakage.
   • Suitable for large prefabricated panel houses or roofs exposed to harsh environments for long periods, offering superior weather resistance and durability with a service life of up to 10-15 years.

3. Thermal Insulation Materials Assisting Waterproofing:

   • Lay thermal insulation materials such as extruded polystyrene boards (XPS) above the waterproof layer to reduce indoor temperature, minimize stress on the prefabricated panels caused by thermal expansion and contraction, and indirectly enhance waterproofing by isolating direct rain impact.
   • Note that a protective layer (such as cement mortar) must be provided between the thermal insulation layer and the waterproof layer to prevent the thermal insulation material from puncturing the waterproof layer.

Key Considerations

• Holistic Treatment: If it is not possible to create grooves to block water paths on the prefabricated panel roof, the entire roof must be waterproofed to avoid water migration from other areas caused by localized repairs.
• Drainage System Optimization: Ensure that the roof slope is reasonable (≥2%) and install drainage outlets or gutters to prevent long-term soaking of the waterproof layer by accumulated water.
• Regular Maintenance: Inspect the condition of the waterproof layer every 2-3 years and promptly repair aged or damaged areas to extend its service life.