How to Waterproof Prefabricated House Slabs

To waterproof prefabricated house slabs, it is necessary to first address the gaps in the base layer and then achieve effective waterproofing through the 'three-scraping and two-pasting' process combined with blocking design. The specific steps are as follows:

1. Base Layer Treatment: Fill Gaps and Enhance Structural Stability

Prefabricated slabs have natural gaps due to their splicing characteristics. If waterproofing is applied directly, cracking may occur due to base layer deformation. First, pour a 5 to 8 cm thick concrete layer on the surface of the prefabricated slabs and lay steel wire mesh. The concrete layer fills the gaps and forms a flat base surface, while the steel wire mesh enhances the tensile strength of the concrete, reducing cracks caused by temperature changes or loads. Ensure the concrete is poured densely to avoid voids, providing a stable foundation for the subsequent waterproof layer.

2. Waterproof Material Selection and the 'Three-Scraping and Two-Pasting' Process

Waterproofing materials should be selected based on the area: For large areas, asphalt is recommended for its weather resistance and low cost; for small areas or complex nodes (such as internal and external corners, pipe roots), JS waterproof coating or sealant can be used for more flexible operation. The 'three-scraping and two-pasting' process is the core technique:

1. First Scraping: Uniformly scrape waterproof material (such as asphalt or JS coating) onto the base layer to form the first waterproof membrane. The thickness should cover the steel wire mesh without any missed areas.
2. First Pasting: After the first layer dries, paste bituminous felt (or polyester non-woven fabric) as a reinforcing layer, ensuring complete adhesion to the base layer with edges overlapping by more than 10 cm to prevent water seepage.
3. Second Scraping: Scrape waterproof material onto the bituminous felt again to fill the fiber gaps and form a continuous waterproof layer.
4. Second Pasting: Repeat the pasting of bituminous felt to enhance the thickness and tear resistance of the waterproof layer.
5. Third Scraping: Finally, scrape waterproof material to seal the surface pores and form a dense protective layer. The 'three-scraping and two-pasting' process creates a multi-layer composite structure that effectively resists water pressure penetration, especially suitable for the cracking-prone characteristics of prefabricated slab roofs.

3. Key Node Treatment: Block Water Seepage Paths

For prefabricated slab roofs, special attention should be paid to the gaps between floor slabs: Before concrete pouring, water stops can be pre-embedded or expanding water stop strips can be filled in the gaps to block horizontal water seepage. Additionally, the roof drainage slope should be ≥2% to avoid water accumulation; R-angle treatment should be done at the junctions of parapet walls, chimneys, and the roof to reduce cracking caused by stress concentration.

4. Post-Construction Maintenance and Acceptance

After the waterproof layer is completed, it should be naturally cured for more than 7 days, avoiding exposure to sunlight or trampling. During acceptance, conduct a 24-hour closed water test. If no leakage is observed, proceed with the construction of the protective layer or surface layer.

By reinforcing the base layer, selecting appropriate materials, optimizing the process, and blocking nodes, the waterproofing challenges of prefabricated slab roofs can be systematically addressed, extending the building's service life.