Conversion of Prefabricated Slab Houses to Cast-in-Place
Converting a prefabricated slab house to a cast-in-place floor slab requires careful implementation, professional structural assessment and verification, and adherence to standardized procedures. The specific steps are as follows:
1. Structural Inspection and Assessment
Before renovation, a qualified inspection agency should be commissioned to conduct a comprehensive evaluation of the house, focusing on the lap length of the prefabricated slab ends on the wall (beam) (standard requirement ≥80mm), concrete strength, steel bar corrosion, slab joints, and wall verticality. If severe cracks at the slab bottom, exposed rebar, or uneven foundation settlement are found, priority should be given to repair or reinforcement; otherwise, the safety of the cast-in-place floor slab may be compromised.
2. Load Verification and Scheme Argumentation
Based on the intended use after renovation (such as adding partition walls, equipment rooms, or accessible roofs), recalculate the dead and live loads on the floor and verify the load-bearing capacity of the existing walls, columns, and foundations. The thickness of the cast-in-place slab is typically 120-150mm, which is heavier than a prefabricated slab. If the original structure's load-bearing capacity is insufficient, the walls or foundations must be reinforced simultaneously to avoid structural damage caused by excessive loads.
3. Scheme Comparison and Selection and Removal of Prefabricated Slabs
There are three main approaches to converting old prefabricated slab houses to cast-in-place structures, with the removal of prefabricated slabs followed by renovation being one of the mainstream methods. During removal, clear the items on the floor and have the work carried out by professionals to avoid safety accidents caused by structural instability. After removal, thoroughly clean the base layer to ensure a flat surface for subsequent construction.
4. Installation of Formwork and Rebar Tying
The formwork, serving as the support for the cast-in-place layer, must ensure a flat surface and sufficient strength; otherwise, it will affect the quality of slab formation and subsequent plastering. When tying the rebar, all main and distribution bars must be inserted and welded into the walls or columns to form an integrated load-bearing structure, preventing local stress concentration on the floor.
5. Pouring and Curing
Use concrete that meets the design strength for pouring. After compaction by vibration, natural curing is required until the strength reaches the standard (usually 28 days), during which premature formwork removal or loading should be avoided. After curing, remove the formwork, check the flatness of the floor surface and any cracks, and make necessary repairs.
Precautions: Renovation has disadvantages such as high cost, long construction period, and significant disturbance to the house, and must strictly comply with regulations. If the original structure is severely aged or the assessment results are unsatisfactory, forced renovation may pose safety risks. It is recommended to prioritize reinforcement or partial renovation schemes.
