Timber Truths: Understanding Durability, Strength and Performance in Australian timber Playgrounds

The timber playground market has become increasingly complex. Asset owners are presented with a growing range of products using both local and imported species, accompanied by durability and service-life claims that can appear comparable on the surface. But the reality is that those claims may be based on different standards, test methods and environmental conditions.

For councils, landscape architects, procurement teams and asset owners, this raises an important question: How do you know which claims you can rely on?

Not All ‘Class 1’ Timber Durability Claims Are Equal

As imported timber playground systems become more common in Australia, it is increasingly important to understand what a durability classification actually represents. While different countries may use similar terminology, the standards are not measuring the same thing in the same way.

Durability classifications are developed within the context of the environment they are intended to represent. Australian standards are based on Australian exposure conditions, while European standards are based on European conditions. Although the classifications may use similar numbering systems, they are not directly interchangeable.

In other words, a Class 1 rating under one standard should not automatically be assumed to represent equivalent performance under another.

How are the standards different?

One of the most significant differences lies not in the rating itself, but in how that rating is
determined. Let’s compare the two most commonly cited standards in playground marketing material in Australia: AS 5604:2022 Timber – Natural durability ratings and EN 350:2016 Durability of wood and woodbased products — Testing and classification of the durability to biological agents of wood and woodbased materials.

AS 5604:2022 is built upon long-term Australian field performance. The classifications are based on expert assessment of timber specimens exposed in Australian environments over decades, resulting in probable service-life categories for both in-ground and above-ground applications.¹

EN 350:2016 takes a different approach. It classifies the natural biological durability of timber
against decay fungi, insects, termites and marine borers using standardised laboratory test methods and supporting durability data.³

Unlike AS 5604:2022, EN 350:2016 does not assign probable years of service life. In fact, the standard itself cautions that biological durability classifications should not be interpreted as a guarantee of performance in service because factors such as climate, design, maintenance and exposure all influence actual lifespan.³

Because the two standards assess durability in different ways, caution should be exercised when comparing durability claims across jurisdictions. This is not a criticism of either standard. Both are appropriate within the context for which they were developed. The challenge arises when a durability classification generated under one system is presented as though it predicts performance in a completely different environment — for example, when durability assessed under European conditions is assumed to predict equivalent performance in Australian public play environments.

Independent research presented to the International Research Group on Wood Protection found that a 10% mass loss in laboratory decay tests was rated anywhere from ‘not resistant’ to ‘very resistant’ depending on which country’s methodology was applied. It concludes that durability classifications should not be expected to be anything more than a rough guide when taken out of geographical context.⁴

Consider a concrete example. Douglas Fir is classified as Durability Class 3 under the European standard EN 350:2016. While EN 350:2016 does not assign service life, some UK guidance has associated Durability Class 3 timbers, including Douglas Fir, with an approximate in-ground service life of 10–15 years under UK conditions.⁵ Under Australian Standard AS 5604:2022, however, the same species is rated Durability Class 4, with an expected in-ground service life of just 0–5 years and less than 7 years above ground.¹

With this in mind, let’s now explore the two species most commonly specified in Australian play environments: Robinia and Australian Ironbark.

Robinia

Robinia (Robinia pseudoacacia) is a European hardwood species that has gained traction in
Australian playgrounds on the strength of its overseas durability reputation. It has a naturally
low sapwood content and, in a European environment, Robinia can perform well in many
exterior applications. However, there is currently no published evidence that Robinia’s durability has been formally tested under Australian conditions.

Without that data, it is not possible to state with certainty how Robinia will perform in Australia
— against Australian termites, Australian UV, Australian soil biology and the extreme cyclical
wetting and drying our climate produces. Any claim regarding Robinia’s long-term durability in Australian public play environments is therefore based on extrapolation rather than Australian field evidence.

What is documented is this: reports of significant cracking, splitting and premature deterioration in Australian Robinia playground equipiment within three to four years of installation. These early-life failures are showing up across Australia, in public environments, on equipment children use daily.

Australian Red Ironbark

Australian Red Ironbark (Eucalyptus sideroxylon) is rated Class 1 Durable under Australian standards — assessed against Australian conditions, in Australian soil, against Australian termites and biological agents. It has an in-ground life expectancy of greater than 25 years, and above ground of greater than 40 years.¹

Beyond formal durability testing, Ironbark has an extensive history of proven performance in
some of Australia’s most demanding structural applications. For generations it has been specified for railway sleepers, bridgework, wharves, poles and the stumps beneath Queenslander homes — applications that demonstrate long-term performance under Australian service conditions.^6,7 Importantly, longevity in these applications was
achieved by using only the naturally durable heartwood. Historically, sapwood was removed by hand with a broad axe or specialised tools.

Beyond Durability

While durability testing provides an important foundation for species selection, it is only one aspect of long-term timber performance. Structural properties, material selection and manufacturing also influence how timber performs throughout its service life.

Playground timber is not simply exposed to the weather. It supports elevated platforms, anchors rope systems and carries repeated dynamic loads as children climb, swing, jump and move across equipment every day.

In a public play environment, timber is a structural material. It anchors tensioned rope systems, supports elevated platforms and absorbs the repeated dynamic forces of children climbing, swinging and jumping — dozens, sometimes hundreds of times a day. The question is not only whether the timber will still be standing in 20 years; it is whether it will perform safely and reliably throughout that time.

While both Robinia and Australian Red Ironbark are recognised hardwoods, they differ structurally. Red Ironbark is one of the densest and hardest commercial timbers in Australia, with a long history in the country’s most demanding structural applications: bridges, wharves, railway sleepers and power poles. Robinia, while a reasonably dense European hardwood, is not classified under the Australian F-grade system — making direct structural grade comparison difficult. What can be compared, however, are physical properties such as
density and hardness, both of which have a direct influence on structural performance.

Australian Red Ironbark is approximately 35% denser than Robinia and has a Janka hardness
almost twice as high. For structural elements expected to carry public loads over decades
of service, these differences warrant careful consideration during equipment selection and
specification.

What should specifiers look for?

A timber durability classification should be treated as one piece of evidence, not the entire specification. When evaluating timber for public play, consider:

• Which durability standard is being referenced?
• Does the evidence reflect Australian conditions?
• Is the claim supported by Australian field data?
• Are the performance claims directly applicable to the environment in which the asset will be installed?

Ultimately, specifying timber for public play is about more than selecting a species with an impressive durability label.

The most meaningful question is not simply whether timber is classified as ‘Class 1’, but what that classification means, how it was established and whether the evidence supports the performance expected in an Australian public play environment.

By looking beyond the label to durability evidence, structural properties, species selection and proven Australian performance, specifiers can make more informed decisions about the long-term performance of timber play equipment.

Read the full white paper

This article is an adapted excerpt from Specifying with Confidence: Rethinking Timber in Public Play, an educational white paper exploring the considerations, challenges and opportunities of specifying timber in public play spaces. Discover practical insights and expert guidance to help inform material selection, design decisions and long-term performance.

Download the full white paper via the link below to explore the complete guide.

References

1. Australian Standard 5604 (2022). Timber — natural durability ratings. Standards Australia, Sydney.
2. Timber Queensland (2014). Technical Data Sheet 25: Outdoor Timber Performance. Timber Queensland, Brisbane.
3. EN 350 (2016). Durability of wood and wood-based products — Testing and classification of the durability to biological agents of wood and wood-based material. European Committee for Standardization, Brussels.
4. Stirling, R (2009). Natural durability classification systems used around the world. The International Research Group on Wood Protection, Sweden. Crossman, M & Simm, J (2004). Manual on the use of timber in coastal and river engineering. Thomas Telford Publishing, London. p.45.
5. Crossman, M & Simm, J (2004). Manual on the use of timber in coastal and river engineering. Thomas Telford Publishing, London. p.45.
6. Queensland Government (2018). Narrow-leaved red ironbark (Eucalyptus crebra). Business Queensland. 12 December. Available at: https://www.business.qld.gov.au/industries/farms-fishing-forestry/forests-wood/properties-timbers/narrow-leaved-red-ironbark
7. Ealing-Godbold, C (2020) Stump capping ceremonies: Laying the foundation of the Queensland weatherboard building. State Library of Queensland. 14 December. Available at: https://www.slq.qld.gov.au/blog/stumpcapping-ceremonies-laying-foundation-queenslandweatherboard-building
8. National Association of Forest Industries (2024). Timber Manual: Datafile P1 – Timber Species and Properties, revised edn. National Association of Forest Industries Ltd, Deakin.
9. Gérard, J, Guibal, D, Paradis, S & Cere, J (2017). Tropical timber atlas. Éditions Quæ, France
10. Center for Wood Anatomy Research (n.d.) Technology transfer fact sheet: Robinia pseudoacacia. USDA Forest Service, Wisconsin.