Roofing & Cladding Tek Screws: Class 3 vs Class 4 Metal & Timber Fasteners
Installing metal roof sheeting, wall cladding, and metal battens requires self-drilling screws (Tek screws) capable of drilling through steel purlins without pre-drilling while providing watertight weather seals.
Under Australian Standard AS 3566 (Self-drilling screws for the building and construction industries), roofing fasteners are classified by corrosion resistance. At Gold Coast Bolt Pro, we supply trade-preferred roofing and cladding screws across South East Queensland.
Understanding AS 3566 Corrosion Classes
The Australian climate requires stringent testing for roofing fasteners exposed to UV, salt, and rainwater.
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Class 1 & 2: Light internal protective coatings suitable for indoor drywall framing and furniture. Not approved for exterior roofing.
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Class 3: Designed for general outdoor weather exposure in mild rural and inland suburban zones (> 1km to 5km from marine spray). Must pass 1,000 hours of neutral salt spray testing.
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Class 4: Heavy-duty protective coating engineered specifically for harsh coastal, high-humidity, and industrial environments (within 1km of ocean spray). Must pass 1,500 hours of salt spray testing.
Anatomy of a Performance Tek Screw
[Hex Flange Head] -- [Neoprene EPDM Washer] -- [Unthreaded Shank] -- [Drill Point]
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Hex Flange Drive: Provides maximum torque transfer without driver bit slippage.
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EPDM Vulcanized Washer: Seals tight around the drill hole, preventing water ingress under heavy rainfall.
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Fluted Drill Point (Tek Point): Cuts through steel purlins (Series 50 points can drill up to 12mm thick structural steel) in a single operation.
Matching Tek Screws to Substrates
1. Metal-to-Timber Roofing Screws
Features a coarse timber thread with a reduced self-drilling point, designed to grip softwood and hardwood roofing battens securely.
2. Light Metal Tek Screws (Series 5)
Engineered for fixing metal roof sheets directly into steel purlins up to 1.9mm–4.5mm thick.
3. Heavy Section Tek Screws (Series 500)
Equipped with extended drill points designed to penetrate thick structural steel beams (up to 12.2mm steel thickness) without snapping or burning out the bit.
Key Installation Guidelines for Roofing Trades
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Do Not Over-Torque: Drive screws until the EPDM washer compresses flush with the metal sheet. Over-torquing crushes the rubber seal, leading to premature roof leaks.
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Clear Swarf Immediately: Steel drill filings (swarf) created during installation will rust rapidly on metal roofs, causing unsightly orange surface spots. Sweep or wash down roof surfaces daily.
Trade Supply of Roofing Screws on the Gold Coast
Stock up on trade packs of Class 3 and Class 4 self-drilling screws, Colorbond-matched roof screws, and hex drivers at Gold Coast Bolt Pro.
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Call Trade Sales: (07) 5500 0000
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Order Online: gcboltpro.com.au