How to Construct the Roof of a Prefabricated Panel Flat House

The construction of the roof of a prefabricated panel flat house requires special attention to base layer treatment, waterproofing, and thermal insulation (optional). The specific steps are as follows:

I. Base Layer Treatment
The base layer is the foundation for roof waterproofing and must be solid, flat, clean, and dry. For the roofs of old prefabricated panel houses, special attention should be paid to panel joint issues: due to thermal expansion and contraction, panel joints are prone to cracking. Directly applying waterproof coatings to cracked joints can easily lead to tearing of the waterproof layer. To address this, first clear debris from the panel joints, then pour 5-8 cm thick fine aggregate concrete, and lay steel wire mesh to enhance crack resistance, ensuring the integrity of the panel joints and the base layer.

II. Waterproofing Treatment
Waterproofing is the core aspect of roof construction and requires meticulous step-by-step operations:

1. Panel Joint Waterproofing Enhancement: After pouring concrete into the panel joints, perform secondary treatment on the panel edges to prevent cracks from appearing along the edges after long-term use.
2. Waterproof Material Selection and Application:
   • For large-area waterproofing, asphalt is recommended, while JS waterproof coatings or sealants can be used for small-area repairs.
   • The construction adopts the 'three-coat, two-layer' method: first apply three coats of waterproof coating (apply the next coat after each coat is surface-dry, with a total thickness ≥1.0mm), then lay two layers of waterproof membrane (such as felt), forming a composite waterproof layer. If asphalt and felt are combined, the waterproof lifespan can reach several decades.
3. Additional Layer Treatment: Additional layers should be applied to areas prone to leakage (such as water spouts, parapet roots, and around pipes):
   • The slope within a 500mm radius around the water spout should be ≥5%, with the additional layer extending into the spout by ≥50mm;
   • The flashing height of the parapet should be ≥250mm, with the additional layer covering 250mm wide on both the flat and vertical surfaces.

III. Thermal Insulation Treatment (Optional)
If enhancing the roof's thermal insulation performance is required, the following two schemes can be adopted:

1. Cold Roof Insulation System: Use spacers to elevate the prefabricated panels, creating an air gap, then lay a leveling layer and a waterproof layer. The air gap promotes steam circulation, preventing condensation inside the roof, but ensure ventilation openings are unobstructed; otherwise, the insulation effect will be reduced.
2. Vapor Barrier Design: After laying a leveling layer on the structural layer, apply hot asphalt or lay one layer of felt with two layers of oil as a vapor barrier to prevent indoor water vapor from infiltrating the insulation layer and causing the insulation material to fail due to moisture.

Precautions: All construction must comply with the requirements of the 'Technical Code for Roof Engineering' GB 50345-2012, especially key parameters such as coating thickness and additional layer dimensions. If the roof is for residential use, it is recommended to complete the waterproof layer first before proceeding with thermal insulation treatment to extend the lifespan of the waterproof layer.