Concrete Prefabricated House Roofing Practice

The roofing practice for concrete prefabricated houses mainly includes construction preparation, insulation layer construction, leveling layer construction, waterproof layer construction, protective layer construction, and other key construction points, as detailed below:

1. Construction Preparation
   Materials should include P.O 42.5 ordinary Portland cement, medium sand (with a silt content ≤ 3%), 5-10mm crushed stone (with a flaky and elongated particle content ≤ 15%), and municipal tap water. The insulation layer should use extruded polystyrene board (XPS, with specifications such as 1800×600×50mm, an apparent density ≥ 32kg/m³, and a thermal conductivity ≤ 0.030W/(m·K)). The waterproof layer should use 4mm thick SBS modified bitumen waterproof membrane (polyester base), with auxiliary materials including cementitious capillary crystalline waterproofing material, polyethylene film isolation layer, and φ4@200×200 cold-drawn low-carbon steel wire mesh. Equipment should include a forced-action mortar mixer, concrete pump, and electric trowel. Structural layer acceptance should ensure that the prefabricated roof panels are installed, with panel joints filled with C30 micro-expanding fine aggregate concrete (depth ≥ half the panel thickness), cured for 7 days, and then tested for load-bearing capacity (panel deflection ≤ L/200), with a surface flatness error ≤ 5mm/2m, internal and external corners rounded to R=50mm, and pipe roots and embedded parts sealed tightly with expanding fireproof sealant.

2. Insulation Layer Construction
   Use 60mm thick XPS board (with a bulk density ≥ 32kg/m³ and a thermal conductivity ≤ 0.030W/(m·K)), which should be constructed after the structural layer has passed acceptance and the leveling layer has dried. XPS board specifications are 600mm×1200mm×60mm, with tongue-and-groove or rabbeted edges for tight splicing. When laying, adjacent panels should be staggered, with gaps filled tightly with the same material. When using the dry-lay method, the panels should be closely adhered to the base layer and laid flat and stable.

3. Leveling Layer Construction
   Use 20mm thick 1:2.5 or 1:3 cement mortar, with a curing time ≥ 7 days, and the surface should be free of looseness, sanding, peeling, and cracks. Before construction, the base layer should be cleaned to ensure it is solid, clean, and flat.

4. Waterproof Layer Construction
   Use 4mm thick SBS modified bitumen waterproof membrane, following the principle of 'details first, then the main surface'. Set additional layers at eaves troughs, roof intersections, water outlets, and pipe roots, with a flashing height ≥ 250mm. The base layer should be solid, clean, and flat, without voids, sanding, or cracks.

5. Protective Layer Construction
   Use 30mm thick C20 fine aggregate concrete, with rounded corners (R=50mm) at base layer corners and intersections with protruding structures, neat and smooth. Before construction, ensure the waterproof layer is dry and undamaged.

6. Other Key Construction Points
   Set the roof drainage slope at 2%, with the slope around water outlets increased to 5% within a 500mm radius. Chisel a 20mm deep circular groove at the root of pipes protruding from the roof, apply an interface treatment agent, and then pour C25 fine aggregate concrete (mixed with 5% expanding agent) to the height of the pipe root. The construction sequence is: accept the structural layer → clean the base layer → prepare adhesive → leveling layer → additional layer → base layer construction → protective layer → curing.