How to Prefabricate Flat House Roof

When prefabricating a flat house roof, it is essential to select an appropriate plan based on the scenario, strictly adhere to construction specifications and material standards, and focus on controlling load-bearing capacity, waterproofing, and structural stability.

I. Applicable Scenarios and Core Limitations

Prefabricated roof panels are suitable for single-story rural bungalows, especially for temporary buildings (construction period of 3-7 days), projects with limited budgets (costs 30%-50% lower than cast-in-place construction), or scenarios with poor geological conditions (soft soil foundations can reduce settlement risks). However, the following limitations must be noted:

• Load-bearing limitations: The load-bearing capacity of a single panel is ≤200kg/㎡. It is prohibited for use in heavy roofs (such as water storage layers or large equipment) or for adding a second story, as this may cause structural deformation or collapse.
• Seismic requirements: In areas with a seismic fortification intensity of 7 degrees or higher, steel structure reinforcement (such as angle steel or channel steel welded supports) is required to enhance overall seismic performance.
• Gap treatment: Gaps between panels must be filled with C20 fine aggregate concrete to prevent rainwater leakage or damage to the structure by small animals.

II. Construction Key Points and Operational Specifications

1. Foundation treatment:
   • A 30cm thick gravel cushion (compaction degree ≥95%) + a 15cm plain concrete leveling layer must be laid to ensure a flat foundation with adequate load-bearing capacity. If the foundation is soft soil, replacement or reinforcement must be carried out in advance.
2. Installation sequence:
   • Installation should proceed block by block from the four corners of the house toward the center, using a staggered joint method (horizontal joint ≥10cm, longitudinal joint ≥20cm) to avoid forming continuous gaps.
3. Waterproofing treatment:
   • After the installation of the roof prefabricated panels is complete, an additional SBS modified asphalt waterproofing layer (thickness ≥4mm) must be laid, and additional layers (width ≥50cm) should be applied at nodes such as parapet walls and chimneys.

III. Material Selection and Quality Standards

• Specification requirements: Commonly used prefabricated panel dimensions are length 3-6m × width 0.5-1.2m × thickness 12-18cm. The appropriate length must be selected based on the house span to avoid breakage due to excessively long panels.
• Strength grade: The concrete strength must be ≥C30, with main reinforcement bars having a diameter ≥8mm and spacing ≤15cm, and stirrup bars having a diameter ≥6mm and spacing ≤25cm to ensure flexural load-bearing capacity.
• International reference plan: When using prefabricated concrete blocks to construct the roof base layer abroad, precision positioning protrusions are designed on both sides of the blocks. A bidirectional ribbed beam structure is formed by pre-laid two rows of wooden planks, with 2-3mm gaps reserved to accommodate thermal expansion and contraction. Stability is ensured through the precise interlocking of the protrusions and ribbed beams. This plan requires extremely high construction precision and must be calibrated with a laser level.

IV. Maintenance and Safety Precautions

• Regularly inspect gaps between panels for cracking. If concrete spalling is found, timely repairs must be made.
• It is prohibited to concentrate heavy objects (such as sand, gravel, or large furniture) on the roof to avoid local overloading.
• In northern regions, roof snow must be cleared in winter to prevent the snow load from exceeding the design value (usually calculated at 50kg/㎡).