Requirements for Roof Materials of Prefabricated Houses

The requirements for roof materials of prefabricated houses mainly include three categories: prefabricated concrete slabs, supporting structural materials, and auxiliary materials. The specific requirements are as follows:

Prefabricated Concrete Slabs

It is necessary to select prestressed hollow prefabricated slabs that comply with the standard GB/T14040-2019 'Prestressed Concrete Hollow Slabs'. The slab type should be determined according to the roof span and load requirements. The commonly used specifications are a length of 3 - 6m, a width of 0.5 - 1.2m, and a thickness of 12 - 18cm. The strength grade should not be lower than the C30 concrete standard. The reinforcement requirements are that the diameter of the main reinforcement should be ≥8mm, and the spacing should be ≤15cm. Upon arrival at the site, it is essential to strictly check the product qualification certificates and mechanical property test reports. Focus on inspecting the slab surface for defects such as cracks, chipped corners, and exposed reinforcement. Slabs with substandard appearance quality should be directly returned to ensure that the material quality meets the standards.

Supporting Structural Materials

For steel bars, the main reinforcement of the beams should use HRB400 grade deformed steel bars, while the stirrups and structural reinforcement should use HPB300 grade plain round steel bars. After arrival at the site, they should be tested in batches for tensile strength, yield strength, and elongation to ensure that the mechanical properties of the steel bars meet the design requirements. Cement should be selected as P·O42.5 grade ordinary Portland cement, ensuring that the 3-day compressive strength is ≥23MPa and the 28-day compressive strength is ≥42.5MPa. At the same time, the soundness index should be tested to avoid affecting the stability of the roof structure due to cement quality issues. For sand and gravel, medium-coarse sand with a mud content ≤3% is required, and the gravel particle size should be controlled within 5 - 25mm with a mud content ≤1%. The use of weathered aggregates is strictly prohibited to ensure the compactness and durability of the concrete.

Auxiliary Materials

Cement mortar should use M15 mixed mortar as the slab joint filling material, with a mix ratio of cement:sand:lime paste = 1:5:0.8 (by weight) to ensure that the slab joints are filled densely and prevent leakage. Waterproof materials can be selected from SBS modified bitumen waterproof membranes (thickness ≥4mm) or polymer cement-based waterproof coatings (film thickness ≥1.5mm). They should have good weather resistance and tensile properties. The roof prefabricated slabs should be additionally provided with an SBS modified bitumen waterproof layer to enhance the waterproof effect. Insulation materials should be selected according to the regional climate, such as extruded polystyrene boards (XPS, thickness 50 - 80mm) or rock wool boards (thickness 60 - 100mm), with a thermal conductivity ≤0.030W/(m·k), effectively improving the thermal insulation performance of the roof and reducing energy consumption.