Plumbing and Wiring in Prefabricated Slab Houses

When conducting plumbing and wiring in prefabricated slab houses, it is essential to strictly adhere to structural safety principles to avoid damaging the load-bearing system of the floor slab. The following are specific operational guidelines:

I. Conduit Installation Methods

1. Prohibition of Slab Trenching Prefabricated floor slabs are hollow structures without reinforced concrete filling. Trenching directly damages the load-bearing framework of the slab, leading to structural safety hazards. All electrical conduits must avoid the slab area and are prohibited from damaging the slab surface through concealed installation methods.

2. Prioritize Utilization of Internal Conduits in Prefabricated Slabs If the prefabricated slab design includes reserved hollow conduits (such as ventilation or structural ducts), insulated wires can be threaded through these natural channels to complete concealed wiring in the roof. It is necessary to confirm the patency of the conduits in advance using an endoscope or metal detector to prevent wire blockages.

3. Standardize Wall Trenching Operations When trenching in brick-concrete structural walls, use a rebar scanner to locate the positions of load-bearing rebars. The trenching depth should not exceed one-third of the wall thickness. For connections between prefabricated slabs and walls (such as ring beam locations), a safety distance of more than 20 cm must be maintained to prevent damage to structural nodes. After trenching, fill with high-strength cement mortar and apply mesh reinforcement to prevent cracking.

4. Rational Utilization of Ceiling Space In areas with suspended ceilings, electrical conduits should be fixed to the side of the ceiling joists using PVC flame-retardant conduits. The conduit diameter should not exceed half of the ceiling joist spacing. Wires must be color-coded and threaded through the conduits (live wire in red, neutral wire in blue, ground wire in yellow-green), and the total cross-sectional area of the conductors in a single conduit should not exceed 40% of the conduit's internal area.

II. Key Construction Considerations

1. Accurate Positioning of Junction Boxes Mark the positions of junction boxes in advance according to the electrical design drawings. When drilling, use an impact drill with a diamond drill bit, with a hole diameter 5 mm larger than the outer diameter of the junction box. The drilling depth should be controlled within the range of the box thickness plus 2 cm to avoid penetrating the hollow layer of the floor slab.

2. Strict Avoidance of Rebar Positions Before conduit installation, confirm the rebar distribution through structural drawings or on-site detection. If rebars are encountered during drilling, stop immediately and adjust the wiring route. Cutting or bending rebars within the prefabricated slab is strictly prohibited; otherwise, a structural engineer must evaluate and propose reinforcement solutions.

3. Reference to Standard Construction Diagrams Specific operations should be carried out in accordance with the node details in Figures 2-55 and 2-56 of the "Residential Decoration and Renovation Engineering Construction Specifications" (GB 50327-2001), focusing on controlling details such as the conduit bending radius (not less than six times the conduit diameter) and the connection method of junction boxes (using locknuts for fixation).

III. Special Structural Treatment Solutions

• Roofs without Reserved Conduits: It is mandatory to adopt suspended ceiling exposed wiring or wall-side wiring solutions. The use of impact drills to drill holes in the floor slab is strictly prohibited. If wiring needs to pass through the floor slab, holes should be drilled at the joints of the prefabricated slabs and sealed with fireproof materials.

• Wiring for Electrical Boxes in Mixed Structures: For conduits extending downward from the electrical box location, trenches should be chiseled in the wall, with a trench width 1 cm larger than the conduit diameter and a depth sufficient to cover the conduit. When laying conduits vertically along the wall, they should be fixed with conduit clamps every 50 cm, and cold bending techniques should be used at bends to maintain the integrity of the conduit walls.

Before implementing any construction plan, the load-bearing system of the house must be confirmed by the original design unit or a qualified structural engineer, and a written renovation opinion must be issued.