Waterproof Requirements for Houses with Prefabricated Floor Slabs

Waterproofing for houses with prefabricated floor slabs requires comprehensive control from multiple aspects, including material selection, construction techniques, post-construction maintenance, and special considerations.

Material Selection: The main material of the prefabricated slab must possess waterproof properties. High-density concrete or fiber cement boards are commonly used. For example, composite floor slabs achieve water resistance through the compactness of the concrete. The surface of the prefabricated slab should be polished or coated to reduce pathways for water penetration. Joint treatment is crucial. Waterproof sealants or elastic joint-filling materials (such as silicone sealant or polyurethane sealant) should be used to fill the gaps between slabs, ensuring seamless joints and preventing water infiltration horizontally or vertically.

Construction Techniques:

1. Base Layer Preparation: Before construction, ensure the base layer is flat, dry, and free of cracks or hollow areas to prevent the failure of the waterproof layer due to base layer defects.
2. Waterproof Layer Installation: Install waterproof membranes (such as SBS modified bitumen membranes) or apply waterproof coatings (such as polyurethane coatings) beneath the prefabricated slabs to form a dual waterproof barrier. Special attention should be given to areas like kitchens, bathrooms, and balconies. The height of the waterproof layer on walls should comply with regulations (e.g., not less than 1.8 meters in shower areas) to prevent water from penetrating through the walls into the slab joints.
3. Installation and Fixing: During the installation of prefabricated slabs, strictly control the spacing to avoid cracking due to uneven stress distribution. Joint treatment should be meticulous. The “one-cloth-three-coats” technique (i.e., applying a waterproof coating, laying a glass fiber cloth, and then applying two additional coats of the waterproof material) can be used to enhance sealing.
4. Secondary Drainage: A secondary drainage outlet should be installed in the backfill layer of bathrooms to ensure that accumulated water can drain smoothly, preventing long-term water accumulation from compromising the waterproof layer.

Post-Construction Maintenance: Regularly inspect the joints and surfaces of the prefabricated slabs for signs of water leakage. Promptly repair any cracks or detachments found. Avoid long-term water accumulation and regularly clean the surfaces to prevent clogging of drainage holes by dirt, which could cause water to backflow into the slab joints.

Special Considerations: In humid regions (such as Chengdu), enhanced waterproofing measures are necessary due to the ease with which moisture can penetrate through walls and slab joints. It is recommended to increase the thickness of the waterproof layer or use more weather-resistant materials. For rural self-built houses with flat roofs and prefabricated slabs, due to cost constraints, consider adding a pitched roof or pouring a cast-in-place slab on the roof. This not only improves thermal insulation but also enhances waterproof performance.