Requirements for Flat Floors in Cement Prefabricated Houses

The construction requirements for flat floors in cement prefabricated houses cover quality objectives, key control points in the construction process, and specific specifications for the leveling layer, as detailed below:

I. Quality Objectives

The flat floor construction must meet the standards of 100% pass rate for sub-projects and ≥95% excellent rate for key processes, strictly adhering to the 'Technical Specification for Prefabricated Concrete Structures' and design documentation requirements. The foundation concrete strength must reach above C30, with a verticality deviation of ≤3mm/m for prefabricated component installation and a surface flatness of ≤5mm/2m, ensuring structural safety and appearance quality.

II. Key Control Points in the Construction Process

1. Foundation Pit Excavation: Utilize a backhoe excavator for operations, reserving 300mm for manual trench clearing at the base to avoid mechanical disturbance to the base soil layer.
2. Foundation Treatment: Lay 300mm thick graded sand and gravel, compacting in layers to achieve a compaction coefficient of ≥0.94, enhancing the foundation's bearing capacity.
3. Rebar Tying: The protective layer thickness for the foundation slab rebar is 50mm, with a tying spacing deviation controlled within ±10mm to ensure accurate rebar positioning.
4. Formwork Installation: Use 18mm thick multi-layer boards, with a support system upright spacing of ≤1.2m to prevent formwork deformation affecting concrete forming quality.
5. Concrete Pouring: Employ C30 ready-mixed concrete, with a layer thickness of ≤500mm, completing secondary troweling before initial setting to reduce surface cracks.
6. Axis Positioning: Conduct layout using a total station, with a deviation controlled within 5mm to ensure precise component installation positioning.

III. Leveling Layer Requirements

1. Solid and Flat: The leveling layer surface should be free of sharp pits or dusting, with a gap of ≤5mm and gradual change when checked with a 2-meter straightedge, with no more than one occurrence per meter.
2. Adjacent Surface Angles: Adjacent surfaces of the leveling layer must be rounded or obtuse to avoid stress concentration leading to cracking.
3. Materials and Thickness: For a solid concrete base, use a 20mm thick cement mortar leveling layer, with a cement mortar ratio of 1:2.5 to 1:3 (by volume) and a cement grade of ≥42.5.
4. Grid Seam Setting: Seams should be 20mm wide, with longitudinal and transverse spacings of ≤6m, aligning grid seams with slab end joints and filling with sealing materials to prevent temperature deformation cracking.
5. Detail Node Treatment:
   • The slope within 500mm around the drip edge should be ≥5%, with a smooth surface;
   • Parapets, roof flues, and stair roots should adopt fine stone concrete fillets with a radius of 80mm;
   • For roof pipeline roots, create a square frustum with a base width of 300mm and a height of 60mm using fine stone concrete, and polish it flat.