GB 15856.4 Hex Head Self-Tapping Screws with EPDM Bonded Washers are high-performance industrial fasteners engineered for heavy-duty metal joining, roofing, and cladding applications. Manufactured from premium carbon steel and protected by standard electro-zinc or hot-dip galvanizing, these screws deliver outstanding mechanical strength, rapid installation, and long-lasting corrosion resistance.

The integrated EPDM bonded washer creates a tight, weatherproof compression seal beneath the hex head, making these screws the premier choice for exterior steel structures, metal roofing sheets, and industrial wall cladding where zero-leakage performance is critical.

• Strict Compliance with GB 15856.4 Standard Precision-engineered to satisfy national standard GB 15856.4 (identical to ISO/DIN international self-tapping screw specifications), ensuring consistent thread pitch, head dimensions, and reliable mechanical properties for global structural projects.
• Superior EPDM Weatherproof Sealing Outfitted with a high-grade EPDM (Ethylene Propylene Diene Monomer) rubber washer bonded to a metal backing. It maintains excellent elasticity and UV resistance under extreme temperature fluctuations, effectively locking out moisture and preventing water seepage around fastener holes.
• High-Strength Carbon Steel & Durable Galvanizing Built from hardened carbon steel for maximum tensile, shear, and torsional resistance during high-speed power tool driving. The uniform zinc-plated surface finish isolates the base metal from ambient humidity, preventing rust and thermal oxidation.
• External Hex Head Design for High-Torque Drive The external hexagon head profile allows full tool engagement with standard hex sockets or nut setters. This minimizes cam-out risks, permits maximum torque transmission without stripping the drive, and accelerates assembly on construction sites.
• Integrated Flat Bearing & Load Distribution The broad washer surface spreads the clamping force over a wider contact area. This prevents over-tightening damage, crushing, or surface cracking on thin sheet metals and coated steel panels.

• Metal Roofing & Wall Cladding: Secure attachment of corrugated steel sheets and sandwich panels to metal or timber purlins.
• Steel Structure Construction: Industrial workshops, warehouses, and prefabricated steel frame buildings.
• HVAC & Ductwork: Assembly of heating, ventilation, and air-conditioning units and metal ducting.
• Automotive & Equipment Enclosures: Sheet metal housings, electrical cabinets, and chassis assembly.

• Standard Export Packaging: Bulk in 20/25 kg cartons plus fumigated wooden pallets.
• Small Box Packaging: Customized polybags or small inner boxes with custom barcode labeling.
• Port of Loading: Ningbo / Shanghai / Lianyungang, China.
• Trade Terms: FOB, CFR, CIF, DDP, DAP.