Waterproofing of Concrete Prefabricated Houses

Taking the assembled prefabricated concrete exterior wall as an example for the waterproofing construction of concrete prefabricated houses, the core principle is 'drainage as the main approach, sealing as a supplement, and multi-layer redundant waterproofing'. It is necessary to strictly follow the 'General Code for Waterproofing of Buildings and Municipal Engineering' (GB55030-2022). The following is an explanation from the aspects of construction preparation, core processes, and key details:

I. Pre-construction Preparation

1. Technical Preparation
   Organize technical personnel to familiarize themselves with the drawings, waterproofing plans, and specifications. Clarify parameters such as joint widths (e.g., vertical joints 15-25mm) and drainage cavity dimensions (cavity width 20mm, depth 15mm). For complex nodes such as wall panel cross-joints and window and door closures, conduct construction briefings and sample demonstrations in advance to confirm process standards and acceptance requirements and avoid blind construction.

2. Material Preparation
   All materials must have quality certificates and test reports. After arriving at the site, they must pass sampling re-inspections before use. Core materials include:

   • Sealant: Select neutral weather-resistant silicone sealant that is compatible with concrete substrates, with weather resistance, elasticity, and adhesion to meet long-term outdoor use requirements;
   • Auxiliary materials: PE foam backer rods (to control sealant joint depth), polyurethane foam (to fill gaps), waterproof expansive dry-hard cement mortar (to repair the substrate), matching primer (to enhance adhesion), and self-compacting micro-expansive concrete (for repairing special parts).

3. Substrate Pre-treatment

   • Clean the substrate around joints and holes. Use high-pressure air blowing, acetone, or alcohol wiping to remove dust, oil, release agents, and other debris, ensuring the substrate is flat, solid, and dry (moisture content ≤ 8%);
   • Repair damaged areas: Use polymer mortar to repair chipped edges and corners on the wall panel surface. Round the internal and external corners to a radius of R ≥ 50mm to ensure the substrate meets standards.

4. Tool and Environment Preparation

   • Equip with specialized tools such as high-pressure air pumps, caulking guns, and scrapers, and conduct pre-use debugging and maintenance;
   • Control the construction environment temperature between 5°C and 35°C. Construction is strictly prohibited in rainy, windy, or frosty weather. Avoid rainwater erosion or external disturbances within 24 hours after construction.

II. Waterproofing Construction of Core Parts (Taking Vertical Joints of Wall Panels as an Example)

1. Substrate Cleaning
   Repeatedly blow the interior of the joint and the substrate within 50mm on both sides with high-pressure air to remove dust. Then, wipe with alcohol to remove oil and let it air dry.

2. Primer Application
   After the substrate is dry, evenly apply the matching primer within a range 5-10mm wider than the sealant joint to ensure no missed applications or accumulations, enhancing the adhesion strength between the sealant and the concrete.

3. Backer Rod Installation
   Embed a PE foam backer rod in the middle of the joint to control the sealant joint depth and form a drainage channel. The diameter of the backer rod should be 10%-20% larger than the width of the sealant joint. Install it continuously without breaks, with the bottom tightly against the bottom of the drainage cavity to ensure the cavity is unobstructed and avoid mortar blockage.

4. Sealant Application
   Use a caulking gun to evenly fill the sealant along the joint to form a continuous sealing layer. After caulking, use a scraper to trim the surface to ensure the sealant joint is full, smooth, and free of bubbles or cracks.

5. Drainage Cavity Treatment
   The bottom of the cavity must not be blocked and must remain unobstructed for drainage, achieving autonomous drainage of accumulated water. The side walls of the cavity can be coated with waterproofing paint for enhanced protection.