Reinforcement of Prefabricated Panels on Old House Roofs

The following methods can be adopted for reinforcing prefabricated panels on old house roofs:

1. Pouring a reinforced concrete 'composite layer'
This method enhances the overall integrity of the prefabricated panels to increase roof rigidity. First, thoroughly clean the surface dust from the prefabricated panels to ensure the base layer is free of oil and loose materials. Then, lay a steel mesh with a diameter of 6 millimeters, with a grid spacing of 20 cm × 20 cm, forming a bidirectional load-bearing system. Finally, pour fine aggregate concrete with a strength not lower than C25, with a recommended thickness of 5-8 cm. Key Points: The steel mesh must be fully adhered to the surface of the prefabricated panels. After pouring the concrete, it should be vibrated densely to avoid honeycombing and pitting. Through the synergistic effect of steel and concrete, the independent prefabricated panels are 'welded' into an integral structure.

2. Structural Inspection and Treatment
Before reinforcement, a comprehensive structural safety assessment of the house is required:

• Crack Inspection: Focus on checking the width of cracks at the production points of the prefabricated panels. If the crack width exceeds 0.3 mm, pressure grouting should be used to inject structural adhesives such as epoxy resin to seal the cracks.
• Connection Inspection: Check the rust rate of the connecting bolts between the prefabricated panels and the ring beams. If the rust rate exceeds 30%, new bolts must be replaced, and the anchoring depth of the bolts should meet the design requirements.
• Load-Bearing Capacity Verification: Evaluate the remaining load-bearing capacity of the roof based on the inspection results to provide data support for subsequent reinforcement plans.

3. Erecting a Temporary Support System
To ensure construction safety, steel pipe supports should be installed every 1.2 meters along the length of the prefabricated panels, with key nodes supported by H-shaped steel beams. The cross-sectional dimensions of the steel beams should be ≥ 200 mm × 200 mm, and they should be fixed to the support system through bolts or welding to form a stable three-dimensional support frame. Precautions: The support system should extend to the foundation layer to ensure a clear load transfer path and avoid local stress concentration.

4. Treating Panel Joints
For panel joint issues identified during structural inspections:

• Remove the original filling material to the solid base layer.
• Implant threaded steel bars with a diameter of 6 mm at intervals of 300 mm, with an implantation depth of ≥ 100 mm.
• Pour C30 fine aggregate concrete and vibrate it densely in two batches. The first pour should reach two-thirds of the height of the panel joint, and the second pour should be carried out after initial setting to achieve a flat surface.

5. Adding Structural Columns
Adding structural columns at the four corners of the house can significantly enhance the overall lateral rigidity:

• The recommended cross-sectional dimensions of the structural columns are 240 mm × 240 mm.
• The longitudinal reinforcement should use a combination of No. 6 and No. 8 steel bars, with stirrup spacing ≤ 200 mm.
• The structural columns should be reliably connected to the floor through embedded parts to form a 'column-panel' collaborative working system, enhancing the spatial rigidity of the roof.