Installation of Precast Slabs for Rural Houses

The installation of precast slabs for rural houses must strictly adhere to the following standards to ensure structural safety and performance:

1. Material Selection and Inspection

• Precast slabs should be purchased from reputable large manufacturers. Reinforcing steel must be prestressed, with a concrete strength grade of no less than C30, and the specifications and quantity of steel must comply with national standards. Common specifications include lengths of 3-6m, widths of 0.5-1.2m, and thicknesses of 12-18cm, with main reinforcement diameters ≥8mm and spacing ≤15cm.
• Visual inspection is crucial: The surface of precast slabs must be free from cracks, honeycombing, holes, and other defects, as these can reduce structural load-bearing capacity and durability.

2. Foundation and Placement Requirements

• The foundation must be compacted and covered with a 30cm thick layer of crushed stone, followed by a 15cm layer of plain concrete for leveling, ensuring flatness and load-bearing capacity.
• The placement of precast slabs must comply with standards: When placed on concrete components (such as ring beams), the support length must be ≥80mm; when placed on walls, the support length must be ≥100mm. Insufficient support length can lead to localized stress concentration and cracking.

3. Installation Standards and Key Points

• Installation Sequence: Install slabs from the corners of the house towards the center, using a staggered joint method to avoid forming continuous seams that weaken overall integrity.
• Gap Treatment: Adjacent precast slabs must have a reserved gap of 20-40mm. After installation, the ends of the slabs should be filled with cement mortar (known as bedding), and the holes at the ends of the slabs in the walls should be filled with concrete to prevent rainwater leakage.
• Load-Bearing Limits: The load-bearing capacity of a single slab must not exceed 200kg/㎡. It is prohibited for use in heavy roofs or second-floor additions, as this may cause structural deformation or collapse.

4. Joint Treatment and Waterproofing Measures

• Debris inside slab joints must be thoroughly cleaned and filled with C20 fine aggregate concrete, which should be vibrated and compacted. If the gap is large (e.g., exceeding 40mm), it should be filled with cast-in-place concrete and cured. The use of bricks for filling is strictly prohibited, as inconsistent material shrinkage can lead to cracking.
• If precast slabs are used for the roof, a steel reinforcement mesh should be laid first, followed by a 6-8mm thick layer of crushed stone concrete to enhance water resistance. Alternatively, an additional layer of SBS modified asphalt waterproofing can be applied to prevent rainwater penetration.

5. Usage Restrictions and Seismic Requirements

• Precast floor slabs must not be arbitrarily cut or notched to avoid damaging the steel reinforcement structure. Due to the dense piping in kitchens and bathrooms, the use of precast slabs is not recommended; cast-in-place floor slabs are preferred.
• In areas with a seismic design intensity of 7 degrees or higher, steel reinforcement (such as additional steel supports or connectors) must be installed. In non-seismic areas, self-built low-rise brick-concrete houses can use precast slabs, but construction must adhere to standards to avoid reducing seismic performance due to construction defects.