Our hardwood and Merbau decking is sold per linear metre in random lengths: you order the total metres and the pack contains a mix of board lengths. On the deck, boards meet end to end at butt joins, and those joins belong over a joist. Plan where they fall, keep them tight, and allow for offcuts. How we price random lengths is covered in how linear metre pricing works; this guide is about laying them out.
Where butt joins go
- Over a joist. Boards that meet end to end are joined over a joist so both ends are supported and fixed.
- Wide enough joists. WoodSolutions' Domestic Timber Deck Design guide recommends wider joists where boards abut over the joist, to reduce splitting, because fixings can then sit further from the board ends. Take joist sizes from your deck design and the installation instructions for the boards you choose.
- Spread them out. The same guide illustrates staggered board layouts rather than joins lined up across the deck.
Keeping joins tight
WoodSolutions recommends a slight under-cut on abutting board ends for a tight fit and pre-drilled holes to reduce splitting. Take fixing distances from board edges and ends from the installation instructions for the boards you choose. Seal the cut ends with your chosen finish before fixing.
Offcuts and your allowance
Because every join lands on a joist, some board ends are cut off, and the length of those offcuts depends on the lengths in your pack and your joist layout. Our timber calculator starts with a 10% wastage allowance, which you can change. A layout with many short runs, angles or cut-outs usually needs more; a simple rectangle with long runs may need less. If your design depends on particular lengths, preferred lengths can be requested by quote.
Gaps: calculator assumption vs installation instructions
Our calculator starts with a 4 mm gap between boards so that it can estimate linear metres. That number is a calculation assumption, not installation advice, and you can change it. The gap you leave on site comes from the installation instructions for the product you buy or from your installer, and the documents differ:
- The STS Decking Storage, Handling and Installation Guide linked on our Stagwood hardwood product pages (Ironbark, Spotted Gum, Forest Red Gum and Gympie Messmate) gives minimum gaps of 5 mm for boards up to 90 mm wide and 8 mm for boards up to 140 mm wide.
- Supplier documents for some products give their own minimums, which are shown on those product pages.
- WoodSolutions publishes a table of recommended gaps at installation that depends on species type, cover width and moisture content.
Where the calculator's gap is below the minimum in the guide we hold for a product, it shows a warning. Follow the instructions for your product; if you are unsure which apply, ask us before you order.
FAQ
Can I get all boards in one length?
Random lengths are standard. Preferred lengths can be requested by quote.
Does the gap change how much I order?
Yes. A wider gap means each board covers more width, so slightly fewer linear metres cover the same area. Enter the gap you will actually use in the calculator.
Where do I start?
Our guides to calculating decking linear metres and how board sizes are measured cover the arithmetic.
Talk to us
Send your deck plan and board choice through request a quote and we will help with the take-off, or browse decking.
Sydney Timber Supply team
Layout and fixing references from WoodSolutions Technical Design Guide 21, Domestic Timber Deck Design (revised October 2020), pages 7, 10, 11 and 18; gap figures from the installation documents linked on our product pages. Reviewed November 2026.