Treatment of Roofs for Old Houses with Prefabricated Panels

The following methods can be referred to for the roof treatment of old houses with prefabricated panels:

1. Professional Assessment and Customized Plan
It is necessary to entrust a qualified testing agency to conduct a comprehensive structural assessment of the house using professional instruments, focusing on checking issues such as wall cracks, steel bar corrosion, foundation settlement, and roof leakage. Develop a targeted plan based on the assessment results:

• Wall cracks: Micro-cracks with a width of less than 0.3 millimeters can be repaired with epoxy resin grouting. If the cracks penetrate the wall or are accompanied by steel bar corrosion, steel plates need to be installed for reinforcement. The thickness of the steel plates should be no less than 4 millimeters and fixed with chemical anchors.
• Roof leakage: The original waterproof layer needs to be completely removed, and the base layer cleaned before laying new waterproof materials. It is recommended to use SBS modified bitumen waterproof membranes (thickness ≥ 4 millimeters) or polyurethane waterproof coatings (coating thickness ≥ 1.5 millimeters), and set a drainage slope (≥ 2%) to ensure smooth drainage.
• Foundation problems: If there is uneven settlement, static pressure piles or root piles should be used for reinforcement. The pile ends should penetrate into the bearing layer by no less than 1 meter, and the single-pile bearing capacity needs to be verified through static load tests.

2. Flat-to-Slope Roof Renovation
Building a sloped roof can solve problems such as leakage and heat insulation, but the bearing capacity of the original structure needs to be strictly calculated:

• Roofing materials: Priority should be given to lightweight materials, such as colored stone metal tiles (self-weight 5-8 kg/m², only 1/6 of that of traditional cement tiles), which can reduce the additional load on the prefabricated panel structure.
• Installation process: Use a lock-and-bite connection method to avoid waterproofing hazards caused by traditional nail-fixing methods. The roof slope is recommended to be controlled between 25° and 35°, which is conducive to drainage and meets wind load requirements.
• Heat insulation performance: The colored sand on the surface of the colored stone metal tiles can reflect more than 70% of solar radiation. Combined with the design of the roof ventilation layer, the indoor temperature in summer can be reduced by 3-5°C.
• Fire prevention and disaster prevention: Class A non-combustible materials need to be selected, and it should be ensured that the roof structure meets the wind pressure resistance design (the basic wind pressure is taken according to a 50-year return period). Colored stone metal tiles can withstand typhoons of magnitude 12 and hail impacts.

3. Government Renovation Projects
Some regions have launched special renovation projects. For example, Nanchang City has implemented full financial subsidy renovations for old urban area houses with prefabricated panel roofs, adopting a "one-building-one-policy" model:

• Application process: Residents can submit renovation applications to the local sub-district office. After the house safety appraisal agency confirms the dangerous building level, the house will be included in the renovation plan.
• Construction standards: The renovation内容包括 [content includes] structural reinforcement, waterproofing redone, and roof renovation. The construction process needs to be subject to quality supervision by the housing and construction department, and the completion acceptance needs to be signed and confirmed by resident representatives.
• Policy coverage: It mainly targets prefabricated panel structure houses built before 1980, giving priority to renovating buildings with serious safety hazards or affecting the urban landscape.