Renovation of Old House Roofs with Prefabricated Panels

The renovation of old house roofs with prefabricated panels requires adherence to scientific processes and strict standards to ensure safety and functional enhancement. Key implementation points are as follows:

I. Structural Safety Assessment Before Renovation is a Core Prerequisite
Before renovation, a professional structural team must conduct a comprehensive inspection of the old house, focusing on assessing the crack width at the prefabricated panel production site. If the crack width exceeds 0.3 millimeters, special treatment measures such as pressure grouting repair or carbon fiber reinforcement must be taken to prevent a decrease in structural load-bearing capacity. Simultaneously, the connection status between the prefabricated panels and the ring beams should be inspected, checking the corrosion rate of the connecting bolts. If the corrosion rate exceeds 30%, they must be replaced with galvanized bolts or chemical anchors that meet current standards to ensure that the connection nodes have sufficient shear and tensile capacity, avoiding the risk of roof collapse due to connection failure.

II. Demolition and Reconstruction Must Maintain Original Height and Structural Stability
Taking the Chongming Zhongxing Town project as an example, renovation should be carried out without changing the original building height. First, completely demolish the original wooden roof and clean the base layer to the surface of the structural layer, ensuring no rotten wood or debris remains. Subsequently, use the concrete cast-in-place process to re-pour the roof. It is recommended that the concrete strength grade be no less than C25, and a double-layer bidirectional steel mesh (diameter ≥ 8mm, spacing ≤ 200mm) should be configured to enhance the overall stiffness and crack resistance of the roof. During the pouring process, strictly control the vibration compactness to avoid defects such as honeycombs and pockmarks that affect waterproof performance.

III. Waterproofing and Durability Design Should be Implemented Simultaneously
After the concrete roof is poured, systematic waterproofing treatment should be carried out. The base layer treatment should be flat and solid, with a slope that meets drainage requirements (generally ≥ 2%). The waterproof layer can adopt double-layer SBS modified asphalt membranes (thickness ≥ 4mm) or polyurethane coatings (coating thickness ≥ 1.5mm), and additional layers should be added at nodes such as parapet walls and roof pipes. It is recommended to lay an insulation layer (such as extruded polystyrene board) or a protective layer (such as cement mortar) above the waterproof layer to extend the service life of the waterproof material and meet the base layer requirements for subsequent roof material laying.

IV. Conditions for Laying Diverse Roof Materials Should be Reserved
After the concrete roof is completed, different types of roof decorative layers can be laid according to needs. For example, if clay tiles or cement tiles are to be laid, counter battens and tile battens should be pre-installed, and the spacing of the keels should conform to the specifications of the tiles. If a metal roof is adopted, a waterproof and breathable membrane should be laid on the concrete surface, and galvanized steel plate bases should be fixed. If asphalt shingles are to be laid directly, a special adhesive should be applied on the waterproof layer to enhance the bonding force between the shingles and the base layer. All laying processes must comply with the requirements of the "Technical Code for Slope Roof Engineering" (GB50693-2011).