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Decking Calculator Australia — Boards, Joists & Materials
Calculate decking boards, joists, and fasteners for your next deck build. Works with standard Australian timber sizes and common decking profiles.
Frequently Asked Questions
How many decking boards do I need per square metre?
For standard 90mm wide boards with 5mm gaps: approximately 10.5 boards per linear metre of width. For 140mm boards: about 6.7 per metre. Use the calculator above for exact quantities based on your deck dimensions.
What spacing should deck joists be in Australia?
Standard joist spacing is 450mm centres for hardwood decking and 400mm centres for softwood or composite. Joists supporting a roof (verandah) may need 600mm centres — check AS 1684 for your specific timber and span.
How much does it cost to build a deck in Australia?
Timber decking costs approximately $300-600 per square metre installed in 2026 (hardwood like Merbau). Composite decking runs $400-800/m². A basic 20m² deck costs $6,000-12,000 depending on height, access, and materials.
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