How to Prefabricate Flat House Roof Panel

The construction of prefabricated flat house roof panels must strictly follow key steps such as material selection, construction preparation, installation and fixation, waterproofing and insulation, and quality inspection. The specific operations are as follows:

I. Material Selection and Adaptability Treatment

1. Specifications and Strength: Preferably select prefabricated panels with a length of 3-6m, width of 0.5-1.2m, and thickness of 12-18cm. The concrete strength should be no less than C30, with main reinforcement diameter ≥8mm and spacing ≤15cm. For prestressed panels, the dimensional error should be ≤±3mm.
2. Environmental Adaptability:
   • Areas with Large Temperature Differences: Reserve 8-12mm expansion joints between panels to prevent cracking due to thermal expansion and contraction.
   • Humid and Rainy Areas: Pre-embed ventilation sleeves with a diameter of 50mm at the bottom of the panels, arranged in a checkerboard pattern with a spacing of 2m to promote air circulation.
   • Severe Cold Areas in the North: Pre-install low-temperature-resistant elastic sealant strips with a Shore hardness of 35±5 in the panel joints to prevent frost heave damage.

II. Construction Preparation and Transportation & Hoisting

1. Foundation Treatment: Lay a 30cm thick gravel cushion + a 15cm plain concrete leveling layer. Use a laser scanner to verify the flatness of the load-bearing walls, and perform secondary leveling if the deviation exceeds 5mm.
2. Transportation and Hoisting:
   • Use a dedicated tray during transportation to prevent the overhanging parts from tilting more than 45°, which could cause breakage.
   • When hoisting with a large tower crane, the distance between hoisting points should not exceed 3/7 of the panel length to avoid local stress concentration.

III. Installation, Fixation, and Joint Treatment

1. Installation Sequence: Install panels block by block from the corners of the house towards the center, with staggered joints. Follow the principle of 'main beams first, then secondary beams'. After positioning, immediately use adjustable steel supports for temporary fixation, with at least 4 support points per panel.
2. Joint Treatment:
   • Three-Stage Method: First, pour up to 2/3 of the joint depth and embed Φ6 anti-crack reinforcement; second, after re-grouting, insert a 10mm thick polyethylene backing strip; finally, seal the surface with polymer cement mortar to form a 45° water diversion slope.
   • Ordinary Joints: Directly fill with C20 fine aggregate concrete to ensure density and no voids.

IV. Waterproofing and Insulation Layer Construction

1. Waterproof Layer: Add an SBS modified asphalt waterproof layer on the roof. Apply three coats of modified asphalt coating at the internal and external corners (each coat should be 0.8-1.2mm thick after drying). An air space layer should be set between the waterproof layer and the insulation layer, with the prefabricated panels elevated by spacers.
2. Insulation Layer: When laying extruded polystyrene boards, stagger the joints by more than half the board length and fix them with U-shaped insulation nails (at least 6 anchor points per square meter). If the insulation layer is set above the structural layer, a vapor barrier layer should be added (e.g., by applying hot asphalt or laying one layer of felt and two layers of oil).

V. Quality Inspection and Maintenance

1. Double-Inspection System: After self-inspection by the team, the quality inspector conducts a 20% random inspection, focusing on monitoring the flatness of the panel bottom (gap ≤4mm detected with a 2m leveling ruler).
2. Maintenance Requirements: Keep the panel surface moist for at least 7 days. In winter construction, cover with double-layer flame-retardant insulation quilts. Grouting operations should be carried out in an environment with humidity ≤70%, and the flowability of the grouting material should be maintained at 240-260mm.

Precautions

• The load-bearing capacity of a single panel should be ≤200kg/㎡, and it is prohibited for use in heavy roofs or second-floor additions.
• In areas with a seismic fortification intensity of 7 degrees or higher, steel structure reinforcement is required; a properly constructed prefabricated panel roof can meet requirements in areas with an 8-degree seismic fortification intensity.