How to Waterproof Prefabricated Houses

Waterproofing for prefabricated houses requires targeted measures for different parts such as roofs, exterior wall joints, and bathrooms, combined with material selection and attention to construction details to form a complete waterproofing system.

1. Waterproofing for Prefabricated Panel Roofs

Prefabricated panel roofs must avoid the issue of "water migration," where local铺设 (laying) of waterproof membranes may fail due to lack of overall treatment. For example, in one case, despite multiple layers of waterproof membranes being laid on the roof, leakage still occurred because the east side was not waterproofed and the west side was only partially treated, allowing water to penetrate through untreated areas. The correct approach is to lay a waterproof layer across the entire roof to ensure no areas are missed. During construction, attention must be paid to the flatness of the base layer to prevent damage to the waterproof layer due to gaps between prefabricated panels. If membranes are used, materials with strong weather resistance and high elongation should be selected, and proper sealing should be done at the joints.

2. Waterproofing for Joints in Prefabricated Exterior Wall Panels

Waterproofing for exterior wall panel joints follows the principle of "diverting water is better than blocking it, and draining water is better than waterproofing," guiding water flow out through structural design:

1. Design Points: Adopt tongue-and-groove joints (higher inside, lower outside) and pressure-relief cavities to use gravity for natural water drainage, preventing capillary backflow.
2. Common Forms:
   • Cast-in-place outer-hung PCF panels: A drainage cavity is provided on the outside and sealed with adhesive, while the inside relies on the self-waterproofing of cast-in-place concrete. However, the cavity is prone to blockage by debris, and concrete cracking can lead to waterproofing failure, requiring regular inspection and maintenance.
   • Externally hung prefabricated wall panels: Three layers of waterproofing are used (weather-resistant silicone on the outside, a pressure-relief cavity in the middle, and waterproof rubber strips on the inside), with additional polyurethane waterproof sealing at cross joints. Drainage pipes are installed every three floors to discharge seepage water, ensuring timely water removal.

3. Waterproofing for Bathrooms in Self-built Houses (Prefabricated Panel Foundations)

Prefabricated panel bathrooms are prone to subsidence and cracking, requiring a combination of materials and construction techniques to enhance waterproofing:

1. Material Selection: Flexible waterproof coatings (such as polyurethane) are used on the floor to accommodate base layer deformation; rigid waterproof coatings (such as JS composite waterproof coatings) are used on the walls to enhance adhesion to the base layer.
2. Construction Steps:
   • Apply a flexible waterproof coating to cover the entire floor and walls up to a certain height (usually not less than 1.8 meters).
   • Lay a polypropylene fabric reinforcement layer, paying attention to "small neck" treatment at pipe openings (wrapping pipe roots with sealing material) to avoid wrinkles or air bubbles.
   • Apply a cement mortar protective layer, and after 24 hours of drying, conduct a closed water test (accumulate water for 24-48 hours) to confirm no leakage before proceeding with the next construction step.

4. General Precautions

Prefabricated assembled buildings have inherent weaknesses in waterproofing due to the large number of joints left by on-site assembly, requiring the use of materials such as rubber waterstops and weather-resistant adhesives to完善 (complete) the system. Construction details are crucial, such as sealing at pipe openings during polypropylene fabric laying and the design of wall joint shapes, all of which must be strictly carried out according to specifications to avoid waterproofing failure due to overlooked details.