1.What are the core principles?
Waterproofing is a priority: Prevents rainwater penetration.
Windproofing reinforcement: Resists wind damage and prevents the structure from being blown away.
Corrosion protection: Protects cuts and joints from electrochemical corrosion.
2.What are the preparatory steps?
Clean the surface: Wipe away dust, oil, and moisture from the overlapping area with a cloth. Ensure the surface is dry and clean; this is a prerequisite for effective adhesion of all sealing materials.
Inspect the sheet materials: Ensure that the galvanized coils and corrugated steel sheets are not deformed and that the overlaps are flat.
3.How to determine the direction and sequence of overlapping?
Overlapping in the direction of water flow: On roofs, slabs on the uphill side should overlap those on the downhill side, like roof tiles, to prevent rainwater from flowing back in. An overlap length of 150-200mm is generally recommended.
Overlapping in the direction of wind: On walls, the same principle applies: the upwind side overlaps the downwind side.
4.How to select and apply sealing materials?
Butyl Rubber Sealing Tape (Most Commonly Used and Recommended)
Advantages: Good adhesion, aging resistance, excellent waterproof performance, and easy application.
Application Method:
Lay a continuous strip of butyl rubber tape at the overlap of the lower sheet (approximately 10-20mm from the edge).
Remove the release paper.
Press the upper sheet onto the tape, applying appropriate pressure to ensure the tape is evenly extruded to a width of approximately 1-2mm.
Polyurethane Sealant (Silicone Glue)
Advantages: Good elasticity and strong adhesion.
Disadvantages: Requires high worker skill for application; susceptible to dust contamination before curing.
Application Method: Use a caulking gun to apply a continuous, even strip of adhesive to the overlap, approximately φ5-8mm in diameter. Then immediately press the sheets together.
5.How should we handle different scenarios?
Scenario 1: Replacement or extension of corrugated steel roofing, overlapping of old and new galvanized sheets
This is the most common scenario. Strictly follow the steps described above, paying particular attention to the overlap direction, butyl tape, and screws with washers.
Scenario 2: Lateral overlap of corrugated steel roofing and galvanized sheets (e.g., splicing different materials)
In addition to standard procedures, pay special attention to the following:
Avoid electrochemical corrosion: If possible, use insulating gaskets or coatings at the contact surfaces of the two metals to interrupt the electrochemical corrosion pathway.
Ensure a tighter seal: Because of the irregular overlap, apply sealant more carefully to ensure all gaps are filled.