How to Install Lights on a Prefabricated Slab Roof

When installing lights on a prefabricated slab roof, you can refer to the following methods and choose the appropriate solution based on the type of light fixture and on-site conditions:

I. Non-Drilling Installation Methods

Ceiling-mounted or adhesive-type light fixtures are the preferred options for installing on a prefabricated slab roof. These fixtures are fixed using suction cups, strong adhesives, or magnetic devices, eliminating the need for drilling holes in the floor slab. This prevents damage to the internal steel reinforcement or prestressed system of the prefabricated slab, ensuring structural safety. For example, lightweight fixtures such as LED ceiling lights and wall lights can be directly adhered or suctioned to the ceiling surface. However, it is essential to ensure that the adhered surface is flat and clean, and that the adhesive or suction cup's load-bearing capacity meets the weight requirements of the fixture. For adhesive-type fixtures, use construction-grade strong adhesive and allow it to cure for at least 24 hours after application.

II. Utilizing Existing Structures for Installation

If the prefabricated slab roof already has auxiliary structures such as suspended ceilings, hanging rods, or light steel keels, these can be used to secure the light fixtures. For example, when installing track lights or downlights on a suspended ceiling frame, use the fixture's配套 (matching) mounting brackets to connect to the keels. If there are pre-installed hanging rods on the roof, the fixture base can be fixed to the end of the hanging rods using expansion bolts. This method requires confirming the load-bearing capacity of the suspended ceiling or hanging rods in advance to avoid overloading.

III. Through-Hole Installation (Suitable for Heavy-Duty Fixtures like Fan Lights)

For installing heavy rotating fixtures such as ceiling fan lights, drilling through the prefabricated slab at the joint or in a steel-free area is necessary:

1. Positioning and Drilling: Select the joint area between two prefabricated slabs (usually free of prestressed holes) and use an electric drill with a diamond bit to drill vertically. The hole diameter should match the ceiling fan's专用 (special) hanger.
2. Upstairs Floor Treatment: Obtain consent from the upstairs resident and install a hanger backplate at the corresponding hole location, securing it to the floor slab with chemical anchors or expansion bolts to ensure a tight connection.
3. Load Reinforcement: A qualified tension plate must be installed at the back of the hanger to distribute the load on the hanging rod. It is recommended to use a finished dedicated hanging rod with a built-in hanger structure at the back, which can effectively resist the shear force and vibration during fan operation. This method must be performed by professionals, and the hanger's load-bearing capacity must be strictly tested (usually requiring at least three times the weight of the fixture).

IV. Four-Bolt Fixing Method (For Joint Installation)

At the joint of prefabricated slabs, four bolt holes can be drilled according to the hanger's requirements, and the fixture base can be fixed using a four-bolt hanger:

1. Positioning: Use a metal detector to confirm that no steel reinforcement crosses the joint, ensuring the bolt holes avoid internal structures.
2. Drilling and Installation: Use an impact drill to create the holes, insert chemical anchors or expansion bolts, and secure the hanger baseplate.
3. Load Testing: After installation, test the hanger's pull-out resistance using a tension gauge to ensure it can withstand the weight of the fixture and dynamic loads. This method is suitable for scenarios without suspended ceilings and requiring heavy-duty fixture installation, but strict adherence to bolt specifications and spacing requirements is necessary.

Installation Precautions

1. Safe Operation: Cut off the power supply before installation, use insulated tools, and wear protective gear.
2. Weight Limitation: The design load of a prefabricated slab is typically 150-200 kg/m². The total weight of the fixture and accessories should not exceed 5 kg to avoid local overloading.
3. Fixation Inspection: After installation, shake the fixture to confirm it is secure. For rotating fixtures, test their operational stability.
4. Professional Assistance: For complex installations (such as through-hole drilling), it is recommended to entrust a licensed electrician to ensure compliance with the "Code for Acceptance of Construction Quality of Building Electrical Engineering" (GB 50303).