How to Waterproof the Roof of a Prefabricated House
Waterproofing the roof of a prefabricated house requires systematic construction, combining material properties with structural characteristics. The following steps can be followed:
1. Comprehensive Roof Inspection and Pre-treatment
Regularly inspect the roof surface, focusing on issues such as cracks, material aging, and peeling, especially in areas prone to leakage like drainage outlets, vent pipes, and parapet walls. Clear debris, dust, and loose particles from the roof, and unclog drainage pipes to prevent water accumulation and leakage risks. If there is water accumulation on the roof, adjust the slope (usually not less than 2%) to ensure smooth drainage.
2. Key Area Focus
Chisel open the base of vent pipes, sewer pipes, and the junction between the parapet wall and the roof, and clean the base layer to a solid structural layer. Use waterproof mortar or elastic sealant to create rounded corners (radius ≥ 50mm) at nodes such as internal and external corners and pipe bases to enhance crack resistance in stress-concentrated areas. The flashing height of the parapet wall should be ≥ 250mm, and a water-retaining step should be set up to prevent rainwater from flowing backward.
3. Base Layer Repair and Cleaning
Thoroughly remove dust and oil stains from the roof using a high-pressure water gun or broom, ensuring the base layer is dry (moisture content ≤ 9%). For cracks with a width < 2mm, fill them with epoxy resin or polyurethane repair agents; for cracks with a width ≥ 2mm, create a V-shaped groove (depth ≥ 15mm) and repair it in layers with waterproof mortar. For locally damaged areas, cut them out to the structural layer and reapply waterproof membranes or coatings.
4. Waterproof Layer Construction
First Waterproof Layer: Apply a 1.5-2mm thick polymer cement-based waterproof coating (such as JS waterproof coating) in 2-3 cross-coats, with a wall upturn height of ≥ 500mm (≥ 1800mm in shower areas). Second Waterproof Layer: After the coating dries, lay a 3mm thick SBS modified asphalt waterproof membrane using hot-melt construction to ensure firm adhesion between the membrane and the base layer, with an overlap width of ≥ 100mm and edge sealing with sealant at the ends.
5. Water Avoidance Test and Protective Layer Construction
After the waterproof layer is completed, close all drainage outlets, fill with water to the design level (usually ≥ 50mm), and observe for 48 hours for no leakage. After passing the test, pour a 40mm thick C20 fine aggregate concrete protective layer with Φ4@100 bidirectional steel mesh, maintaining the same slope as the original roof, surface troweling, and setting division joints (spacing ≤ 3m) to prevent cracking.
6. Long-term Maintenance and Management
Clear debris from the roof every six months and check the drainage system for smoothness; inspect the waterproof layer annually, focusing on the membrane overlap areas and node sealing; conduct a comprehensive inspection after extreme weather (such as heavy rain or hail) and repair any damage promptly. Avoid stacking heavy or sharp objects on the roof to prevent damage to the waterproof layer.
