Iron Bark Decking

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SKU: GHT-6016 Category: Timber Decking Brand: Greenhill Timbers Grades: Standard and Better Profile: DAR Janka Rating: 16

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Grey ironbark decking in 86 × 19 mm and 135 × 19 mm: one of the hardest Australian hardwoods, with Janka hardness 16 kN, Class 1 durability both above ground and in-ground, and rated for bushfire decking up to BAL-19.

Sizes: 86 × 19 mm and 135 × 19 mm
Timber: grey ironbark (Eucalyptus paniculata and E. drepanophylla), grown in NSW and Queensland; reddish-brown to dark brown; about 1105–1120 kg/m³, the densest timber in our decking range
Durability: Class 1 above ground, which the Queensland Government rates at more than 40 years’ expected life; Class 1 in-ground too; the heartwood is termite resistant and the sapwood isn’t susceptible to lyctid borer
Bushfire: qualifies under AS 3959’s high-density rule for BAL-12.5 and BAL-19, but it is not on the bushfire-resisting timber list, so it can’t be used for decking at BAL-29. For BAL-29, choose Spotted Gum, Blackbutt or Merbau
Joist spacing: 450 mm centres, as WoodSolutions recommends for decking; its deck design guide allows up to 500 mm for 19 mm hardwood, or 350 mm if the boards run at 45°
Gaps: 3–4 mm between 86 mm boards and 4–5 mm between 135 mm boards at installation (WoodSolutions deck design guide)
How much for a deck: a 20 m² deck needs about 140 lineal metres of 135 mm board or about 225 lineal metres of 86 mm, plus about 10% for offcuts
Low decks: under 400 mm off the ground, WoodSolutions suggests 5–6 mm gaps and at least 40 mm between the deck and the house, for airflow
Fixing: two fixings per board at every joist, at least 12 mm from edges and ends. Pre-drill this dense hardwood. Use stainless steel within 1 km of the coast or 1 m of a pool. See our decking screws
Finishing: coat every face and cut end, ideally before fixing, then recoat at least once a year or as the oil maker directs (WoodSolutions); left bare, it weathers to silver-grey. Oils we stock: CUTEK CD50, Intergrain Universal Timber Oil or Sceney’s Timber Decking Oil
At Greenhill: stocked at 170 Settlement Road, Thomastown, with pickup or delivery across Melbourne and regional Victoria. Compare species on our hardwood decking page.

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Product Description

What Makes Iron Bark Decking a Strong Choice?

Iron bark timber decking stands out for its density, longevity, and resistance to the elements. It’s a popular option for builders and landscapers who need a decking material that can withstand pressure.

Used across everything from coastal decks to public walkways and large outdoor entertaining areas, Iron Bark holds its shape under load, and doesn’t wear easily.

Its natural tones range from rich reddish browns to muted greys, offering a grounded, earthy look that works in a variety of architectural styles. Over time, the colour can soften with weather exposure, but the board’s integrity stays solid.

Reliable in Harsh Australian Conditions

Iron bark timber decking is well suited to outdoor use across a wide range of sites. Our ironbark is grey ironbark. With a Janka hardness of 16 kN, it is among the toughest decking timbers available. It is rated for bushfire decking up to BAL-19.

Naturally resistant to termites, rot, and moisture-related movement, Iron Bark is especially valued for projects where maintenance access is limited or performance is critical. Pre-drilling is typically required, but the trade-off is a stable, long-lasting board that won’t twist or lift once installed.

Iron Bark Decking Sizes: 86 x 19 and 135 x19 h2

Greenhill Timbers supplies:

Iron Bark Decking 86 x 19
Iron Bark Decking 135 x 19

These sizes suit both traditional and modern deck layouts, giving you options for coverage and board spacing. If you’re unsure which size fits your job best, our team can help you plan quantities and layout.

Supplied by Greenhill Timbers

We work closely with builders and DIY customers across Melbourne and regional Victoria, supplying high-grade iron bark decking that performs on-site. If you’re after strength, compliance, and durability, without constant upkeep, iron bark timber decking is a smart investment.

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Janka Rating

Iron Bark Decking — Janka hardness: 16 kN

What Is the Janka Rating?

The Janka rating is a way to measure how hard a timber is, specifically, how much force it takes to push a small steel ball halfway into the wood. The number you get is shown in kilonewtons (kN). A higher Janka score means a harder, more durable timber. Builders and floor installers use it to work out which timbers hold up better in busy areas.

Here’s a rough guide to how some timbers sit on the scale:

Brazilian Walnut – around 16.0 kN
Spotted Gum – roughly 11.0 kN
Tasmanian Oak – about 5.5 kN
Radiata Pine – close to 3.0 kN

Keep in mind: these values can vary depending on moisture content and grain direction.

It's One Part of the Decision

Hardness is useful to know, but it’s just one factor. Janka doesn’t tell you how a timber reacts to heat or humidity, how stable it is, or how easy it is to cut and install.

Some of the hardest woods can be difficult to work with. Others, even if softer, might be more stable or forgiving on-site.

At Greenhill Timbers, we look at the whole picture, not just the numbers. All our timbers are structurally graded and covered by a 25-year guarantee. We'll help you pick something that works for your project, not just on paper.

Delivery Options

Melbourne-Wide Delivery

We carefully prepare your order and organise pick-up or delivery that suits your schedule, ensuring your satisfaction when you choose to purchase from us. If you're located in Melbourne and its surrounding areas, you can collect your order from our Thomastown Showroom at 170 Settlement Road. Otherwise, we can facilitate delivery by leveraging our strong partnerships with various sub-contractors to get you the most competitive delivery rate and suitable time frame. For more information, get in touch with us.

Why Choose Us

Get Your Timber Packed

We pack, wrap and load your products into your vehicle on-site. As a Green Hill customer, you won’t have to pack your timber or lug it into your vehicle after you’ve purchased it.

One Stop Shop

We are a one-stop shop for all your timber needs. Get dozens of types of wood, both imported and local, and the right cuts for your decking, flooring, cladding and fencing projects.

Competitive Pricing

In most cases, we can help you save hundreds or even thousands of dollars on the same materials compared to other timber suppliers.

Expert Staff

Our expert staff will assist you in finding the perfect timber to match your projects based on a relaxed chat to find what you need.

Transparent Quotes

We give you the whole picture when we quote you. So you can avoid any nasty surprises down the line.