Factory Building Roof Prefabrication Methods

Factory building roof prefabrication methods mainly include general prefabricated roof component processes and prefabricated panel roof construction methods. The prefabrication method for the trough-shaped panels of the roof of a hydropower station building mentions the earth mold method but does not elaborate on it. The following is the specific content:

General Prefabricated Roof Component Processes

• Preliminary Preparations:
  • Technical Preparations: Deepen the design by adjusting component dimensions according to the actual construction errors of the on-site main structure and considering transportation width and height restrictions. Plan in advance details such as the roof drainage slope, gutters, ventilation openings, and reserved positions for solar panels. Mark the positions of embedded parts and reserved holes, and verify the connection joints and对接 (this Chinese word might need more context for a perfect translation, here it's translated as '对接' which means 'connection' in general sense, but a more precise term could be used if more context is available) dimensions with the main structure. Conduct technical disclosures after completion.
  • Mold and Material Preparations: Use steel molds. Upon arrival, check the dimensional flatness, reserved slots, positioning holes for embedded parts, and gaps, and apply a uniform release agent. Send steel bars for inspection in advance, ensuring that the model and spacing meet design requirements and that the protective layer thickness is sufficient. Prepare the concrete mix ratio in advance, adding an appropriate amount of waterproofing agent, and ensure the concrete grade meets design requirements. Pre-inspect auxiliary materials such as embedded lifting parts, connecting bolts, and waterproof sealants before they enter the site.
  • Site and Personnel Organization: The factory production site should be flat and hardened, and lifting equipment should be inspected in advance. Determine the finished product storage site.

Prefabricated Panel Roof Construction Methods

• Material Selection: When selecting prestressed concrete prefabricated panels, ensure that the dimensional error of each panel is controlled within ±3mm. Use C30-grade concrete for the laminated layer, with the coarse aggregate particle size being less than one-third of the laminated layer thickness. In areas with large temperature differences, reserve 8 - 12mm expansion spaces between panel joints. Use special pallets for transportation to prevent the overhanging parts from having an inclination angle of more than 45°.
• Pre-construction Preparations: Use a laser scanner to verify the three-dimensional coordinates of the load-bearing walls. Areas with a flatness deviation exceeding 5mm should be re-leveled. In humid and rainy areas, embed 50mm-diameter ventilation sleeves at the panel bottom, arranged in a checkerboard pattern with a 2m spacing. Electricians should avoid embedding wire conduits in the positions of truss bars.
• Installation Procedures: Follow the principle of 'main beams first, then secondary beams'. When using a large tower crane for lifting, the distance between lifting points should not exceed three-sevenths of the panel length. Immediately use adjustable steel supports to temporarily fix the panel ends upon placement, with no less than four support points for a single panel.
• Joint Treatment: Adopt a three-stage method. First, pour to two-thirds of the joint depth and embed Φ6 anti-crack bars. After secondary grouting, insert a 10mm-thick polyethylene backing strip. Seal the surface with polymer cement mortar to form a 45° water-diverting slope. In severely cold regions in the north, pre-install low-temperature-resistant elastic sealant strips in the panel joints, with a Shore hardness controlled at 35±5.
• Waterproof Layer Construction: Pay attention to the treatment of internal and external corners. Apply three coats of modified asphalt coating, with each coat forming a thickness of 0.8 - 1.2mm after drying.