Calculating The Right Amount Of Decking Timber In Sydney

There’s definitely something uniquely satisfying about planning a new deck. You can already picture summer afternoons with friends and family, kids running barefoot, and the barbie sizzling. 

But before the first nail can be hammered in, you need to calculate the right amount of decking timber. In Sydney, many DIYers and even seasoned renovators misjudge this crucial aspect and end up wasting money, causing delays, or needing to rework parts of the deck. 

Getting this building material calculation right upfront can save you time and money, whether you’re building a small backyard platform or a full wrap-around. 

Here’s what you need to know to get it right the first time:

Calculate Your Deck’s Total Area

The first step towards calculating the right amount of decking timber in Sydney is to work out the total square meterage of your deck. This sounds obvious, but mistakes are often made in this very first stage. 

Measure the length and width of the area that you want to cover, and multiply them to get your total area in square metres. 

For example: 5 m x 4 m = 20 m²

If your deck includes steps, built-in seating, or irregular shapes, then you need to take the time to break the project into rectangles and triangles to calculate each separately before adding them all together.

Once you’ve got your total area worked out, you can begin estimating how many linear metres of decking timber you’ll need. The calculation for this will depend on the size of the boards that you choose, and it’s here where things get more precise.

Consider Board Size And Spacing

Decking boards typically come in standard widths of 90 mm, 140 mm, or 150 mm. The narrower the board, the more of them you’ll need. 

To determine exactly how many linear metres you’ll need per square metre of decking, divide one by the board width in metres and add a spacing factor. A typical gap between decking boards is around 3 mm to 5 mm to allow for expansion, drainage, and airflow.

Let’s say you’re using 90 mm wide boards (0.09 m) and you’re allowing for a 5 mm (0.005 m) gap. That brings your effective board + gap width to 0.095 m. 

Therefore: 1 ÷ 0.095 = approximately 10.53 linear metres per m²

So, if your deck is 20 m², you’ll need roughly 20 x 10.53 = 210.6 linear metres of decking timber.

It’s always a good idea to also round up slightly to allow for offcuts and waste. Generally, a 5% to 10% buffer is recommended. So in the example above, you should probably order around 230 linear metres in total to be safe.

Consider Timber Type And Length Availability

Another important factor that you need to take into account is the species of decking timber in Sydney you choose and the lengths that are available. Australian hardwoods like spotted gum or Merbau are popular in Sydney for their durability and rich colour, but they can be more expensive than treated pine. 

Furthermore, some timbers might only be available in specific lengths, so if your design includes long spans, then you should consider planning around available stock. You’ll also want to minimise joins wherever possible for both aesthetic and structural reasons. However, this might affect your timber order, so check what’s available before you finalise your plan.

Think About Framing And Hidden Costs

Your decking project doesn’t just end with the boards. Joists, bearers, fixings, sealants, and treatments all form part of the bigger picture. While these won’t necessarily affect your decking timber calculation directly, they can have an influence on how your deck is laid out and supported. 

A more complex frame may increase offcut waste, so you might find it worthwhile revisiting your calculations if your design evolves.

Are you planning your next outdoor build? For quality decking timber in Sydney at unbeatable value, contact us at Renovator Auctions today and get expert guidance on your timber needs.