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Screws for Decking
Measure across the outside of the thread - not the shank - to get the gauge (a 10g decking screw measures about 4.8mm). Screw gauges have a wider tolerance than bolts, so treat it as a close match rather than exact. Then measure the overall length, head included - decking screws are countersunk.
Every product page carries a Screw Gauge and TPI chart for its range - every gauge links straight to the product. Coarse threads suit treated pine and softwood decking; fine threads suit hardwood boards like merbau and spotted gum.
Decking Screws - Timber, Metal & Hidden Fasteners
Bolt & Nut Australia stocks the decking screw range for Australian outdoor builds: stainless and galvanised screws for timber substructures, self-drilling screws for metal joists and bearers, pre-packed bundles sized to common deck builds, and the driver bits and hidden-fastener tools you need to install them.
Decking lives outside. The screws hold the deck flat through summer expansion, winter contraction, rain, UV and ground splash for 20+ years. We stock the right finish for each environment: hot-dip galvanised Class 3 / Class 4 / Hobson DX-coatings for inland Australian decks, Stainless A2-70 G304 for coastal areas under shelter, Stainless A4-70 G316 marine grade within 300m of the sea, and Bi-Metal stainless heads with carbon steel drill points for fixing into thick metal.
Choosing the Right Decking Screw
Match the screw to your substructure. Timber joists take Type 17 self-tapping decking screws (point drills its own pilot hole, threads hold in softwood and hardwood). Metal joists take self-drilling screws with a wing-tip drill point sized to cut through the metal thickness without splitting the timber board on the way in. The deck board itself dictates the head style: countersunk for hardwood (sits flush, paintable plug if desired), Bugle-batten for softwood (wider bearing for a softer fibre).
Our Range
Browse: Screws Only for Metal · Screws Only for Timber · Decking Screw Bundles · Decking Tools
Coatings & Materials
Hot-dip galvanised carbon steel - the standard outdoor finish for inland decks. Thick zinc coating gives 20-50 years of outdoor service. Class 3 and Class 4 are sequential Australian Standard ratings. Hobson DX3 and DX4 are the equivalent Hobson branding. X9 is Class 4 with Hobson finish.
Stainless A2-70 G304 - standard stainless grade. Suits external Australian environments and coastal use under shelter. Used in food, dairy, mining and general outdoor work.
Stainless A4-70 G316 - marine grade. Adds 2-3% molybdenum to resist chloride attack. The right choice within 300m of the sea or for permanently wet applications.
Stainless G410 (martensitic) - hardened stainless used on self-drilling decking screws. Higher hardness than A2 / A4 lets the screw cut through dense hardwood and thin metal without the drill point softening. Trade-off is moderate corrosion resistance - suitable for inland and lightly coastal decks; not a substitute for G316 within 300m of the sea or in permanently wet locations.
Bi-Metal stainless / carbon - stainless head and shank welded to a carbon-steel drill point. Gives a hardened tip for self-drilling into thicker metal while keeping the corrosion-resistant body for outdoor service.
See our full galvanised coatings comparison chart for side-by-side ratings, salt-spray test results and recommended use cases.
Technical Resources
See our Technical PDF's Library for CAD drawings, specification sheets and installation guides covering decking screws and tools. Use our Screw Gauge sizing chart to convert between gauge (8g, 10g, 12g, 14g) and metric body diameter.
Frequently Asked Questions
What screw do I need for a hardwood deck on timber joists?
A countersunk Type 17 self-tapping decking screw in stainless G316 (coastal) or G304 (inland) sized 10g or 12g x 65mm-75mm. Countersunk head sits flush with the deck face for a clean finish and accepts a paintable plug if desired.
Can I use galvanised screws in a hardwood deck like Jarrah or Merbau?
No - tannins in hardwoods like Jarrah, Merbau and Spotted Gum react with zinc and cause black staining around the screw head. Use stainless steel in hardwoods (G304 inland, G316 within 300m of the sea).
What's the difference between Type 17 and self-drilling?
Type 17 has a sharp self-tapping point that bores its own pilot in timber. Self-drilling has a wing-tip or drill-point head that cuts through metal. Match the point to the substrate - Type 17 for timber joists, self-drilling for steel joists.
Bugle-batten or countersunk head?
Bugle-batten has a wider bearing surface that grips softer timber without crushing the fibres. Use it on softwood decks (pine, treated pine). Countersunk has a smaller flush head suitable for harder timber. Use it on hardwood decks (Jarrah, Merbau, Spotted Gum).
How far apart should decking screws be?
Two screws per board at every joist. Set them 15-20mm from each edge of the board so the screw bites timber not air. Pre-drilling is optional on softwood, required on dense hardwoods (3mm pilot, deep enough to take the full screw length).
Hidden-fastener system or face-fix?
Hidden fasteners give a clean face but require deck boards with a side groove. Most builders use face-fix decking screws because they're faster, cheaper and the screw heads disappear when stained to match the deck. Both methods are mechanically sound.
What's the minimum thickness of metal joist a self-drilling screw will fix into?
Wing-tip self-drillers go through up to 5mm steel; bi-metal decking screws handle 3-12mm. Match the drill-point length to the metal thickness - too short and the threads start cutting before the point exits the back face, splitting the board edge.
Do I need pre-drilling on the deck board?
On softwood (treated pine, radiata) - no. The Type 17 point self-drills the timber. On hardwood (Jarrah, Merbau, Spotted Gum) - yes, pre-drill a 3mm pilot through the board to prevent splitting and ease the screw home. Pre-drilling also stops the head crushing the timber surface as it seats.
Will the screws rust if water sits on the deck?
Galvanised will eventually rust if water pools at the screw head; stainless will not. For decks that get permanently wet (pool surrounds, exposed coastal) use stainless G316. For decks that dry between rain events use galvanised Class 4 or stainless G304.
How many screws in a typical deck build?
Around 6 screws per square metre on a 90mm-board deck with 450mm joist spacing - i.e. roughly 240 screws per 40m² deck. Our decking screw bundles are pre-sized to standard deck builds; see the Decking Screw Bundles sub-cat for the size-and-quantity guide.
We've been supplying these online from Brisbane for over 15 years. With 25,000 stock lines and over 200 million pieces in stock, we carry one of the most comprehensive ranges of decking screws available in Australia — from single-piece loose stock to bundle packs sized to standard deck builds. Save more as you buy more — we offer up to 13 price breaks plus 3 spend-tier discounts.
Why Australia Trusts Bolt & Nut
98.75% of orders ship the same business day when placed before 1pm AEST. We've been online since 2011, carry 25,000 stock lines and over 200 million pieces ex-stock in Brisbane QLD, and offer up to 13 price breaks plus 3 spend-tier discounts. See our verified customer reviews on REVIEWS.io.
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Decking Screw Bundles -
Decking Tools -
Screws only for Metal -
Screws only for Timber
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3.2mm x 46mm Replacement Drill Bits for 8g Hobson EZ-Bit Decking Tool LB-00502As low as $11.050 each -
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3.6mm x 46mm Replacement Drill Bits for 10g Hobson EZ-Bit Decking Tool LB-00503As low as $11.050 each -
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Decking screws for Australian outdoor builds. Type 17 self-tappers for timber joists, self-drilling for metal joists, pre-packed bundles sized to standard deck builds, and the driver bits and hidden-fastener tools to install them. Galvanised, stainless G304 and G316, bi-metal.
