How to Waterproof Prefabricated Houses

The following methods can be adopted for waterproofing prefabricated houses, which require systematic treatment based on structural characteristics and material properties:

I. Reinforcement and Waterproof Pre-treatment of Prefabricated Panel Gaps
Natural gaps exist between the panels of prefabricated houses, which are the main hidden danger for leakage. It is essential to first structurally reinforce these gaps: Pour a 5 to 8 cm thick concrete layer on the surface of the prefabricated panels and embed steel wire mesh within it. The role of the steel wire mesh is to enhance the bonding strength between the concrete and the prefabricated panels, preventing cracking of the concrete layer due to temperature changes or foundation settlement. Meanwhile, the mesh spacing of the steel wire mesh should be controlled between 10 to 15 cm to ensure uniform stress dispersion. After pouring, the concrete requires sufficient curing to avoid shrinkage cracks caused by rapid water loss. This step not only fills the gaps but also provides a flat and sturdy base layer for the subsequent waterproof layer.

II. Layered Construction of Waterproof Materials and the 'Three-Scraping, Two-Laying' Process
The construction of the waterproof layer should follow the core principle of 'three-scraping, two-laying', which involves forming a composite waterproof barrier through three layers of coating and two layers of laying.

1. Base Layer Treatment: After the concrete layer is completely dry, clean the surface of dust and particles to ensure no sharp objects protrude. If there are minor cracks in the base layer, use a leak-stopping agent (such as polyurethane-based) for local repair before proceeding with large-scale construction.
2. First Layer Coating: Apply the first coat using asphalt or JS waterproof coating (polymer cement-based waterproof coating), with a thickness controlled between 0.5 to 1 mm. Asphalt is suitable for large-scale outdoor construction due to its strong weather resistance; JS coating is more suitable for indoor or humid environments due to its superior environmental friendliness. When applying, use the 'cross-coating method' to ensure no missed spots.
3. First Layer Laying: While the first coat is not completely dry, lay bituminous felt (or fiberglass cloth) as a reinforcing layer. The bituminous felt should be laid flat, with edges overlapping by no less than 10 cm, and pressed down with a brush to remove air bubbles.
4. Second and Third Layer Coating: Repeat the above coating steps, gradually increasing the thickness of each layer, with a final total thickness of no less than 2 mm. Multiple layers of coating can fill any pinhole defects that may exist in a single layer, forming a dense waterproof membrane.
5. Second Layer Laying: When the third coat is semi-dry, lay bituminous felt again to form a 'sandwich' structure. This step significantly enhances the tear resistance of the waterproof layer, especially suitable for roofs or areas exposed to the outdoors for long periods.

III. Reinforced Treatment of Detail Areas
Nodes such as internal and external corners and pipe penetrations in prefabricated houses require additional reinforcement:

• Internal and External Corners: Use waterproof mortar to form a circular arc with a radius of no less than 5 cm to reduce stress concentration.
• Pipe Roots: Apply a leak-stopping agent around the pipes and wrap with fiberglass cloth to form a 'root reinforcement ring'.
• Drainage Outlets: Ensure the drainage slope meets design requirements (generally no less than 2%) to avoid water backflow.

Through structural reinforcement, layered construction, and detail reinforcement, the waterproof system of prefabricated houses can achieve long-term reliability, effectively resisting rainwater penetration and moisture erosion.