What is AS 5604?
AS 5604 is the Australian Standard for Timber Durability, published by Standards Australia. Its full designation is AS 5604-2005: Timber, Natural Durability Ratings. The standard defines how long different timber species will resist decay and biological attack when used in various service conditions, both above ground and in-ground contact.
The standard covers the natural durability of untreated timber. It does not assess treated timber, which falls under a separate standard. AS 5604 is the primary reference document used by architects, engineers, specifiers and procurement officers when selecting timber for outdoor applications across Australia.
For buyers of outdoor furniture, picnic tables and park seating, AS 5604 provides a clear, evidence-based framework for comparing species and making decisions that will last decades rather than years.
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The Four Durability Classes
AS 5604 divides timber species into four durability classes based on expected service life. The classification applies separately to in-ground and above-ground use, because soil contact dramatically accelerates decay for most species.
| Class | Description | In-Ground Life | Above-Ground Life | Examples |
|---|---|---|---|---|
| Class 1 | Highly Durable | 25+ years | 40+ years | Spotted Gum, Ironbark, Grey Ironbark, QLD Red Gum |
| Class 2 | Durable | 15-25 years | 25-40 years | Merbau, Tallowwood |
| Class 3 | Moderately Durable | 5-10 years | 7-15 years | White Cypress Pine |
| Class 4 | Non-Durable | 1-5 years | 1-7 years | Most imported softwoods |
The above-ground life figures assume the timber is exposed to weather but not in contact with soil or moisture traps. In practice, a well-maintained Class 1 hardwood picnic table kept clean and re-oiled periodically will exceed the 40-year above-ground benchmark.
Which Timber Species Carry Class 1 Rating?
Class 1 is the highest durability rating under AS 5604. The following species are certified Class 1 and are commonly used in Australian outdoor furniture manufacturing.
Spotted Gum (Corymbia citriodora) is one of Australia's most widely used structural hardwoods. It carries a Class 1 durability rating and a Janka hardness of 11.0 kN. Its natural silica and oil content resist moisture absorption without chemical treatment. The interlocked grain produces a distinctive appearance that weathers to a silver-grey if left unfinished, or retains warm tones when oiled.
Ironbark (Eucalyptus sideroxylon) is among the densest commercial hardwoods in the world, with a Janka rating of 14.0 kN. Class 1 rated, it is exceptionally resistant to decay, termite attack and surface wear. It is the preferred species for high-traffic commercial installations including council parks and school furniture.
Merbau (Intsia bijuga) is a Class 1 tropical hardwood widely used across Australia for decking and outdoor furniture. With a Janka rating of 8.6 kN, it is slightly softer than the eucalypt species but retains Class 1 durability due to its natural oil content. It is an excellent choice for above-ground outdoor applications.
QLD Red Gum (Eucalyptus tereticornis) carries Class 1 rating with a Janka hardness of approximately 11.0 kN. Its rich red-brown heartwood is visually distinctive. Like other Class 1 eucalypts, it does not require chemical treatment for outdoor use.
All timber species used by Auscraft Furniture carry AS 5604 Class 1 durability rating, the highest classification available under Australian Standards.
AS 5604 and Treated Timber
AS 5604 covers the natural durability of untreated timber only. It does not apply to timber that has been chemically treated to improve its durability. Treated timber products, including CCA-treated pine, ACQ-treated pine and other preservative-treated species, are covered by a separate standard: AS 1604.
This distinction matters for buyers. A species classified as Class 4 under AS 5604 (non-durable in its natural state) can potentially be treated to achieve outdoor suitability, but that treated durability is governed by AS 1604, not AS 5604. The two standards should not be confused or conflated in specification documents.
For public outdoor furniture, specifiers increasingly prefer Class 1 natural hardwoods over treated softwoods because they eliminate the risk of chemical leaching in children's play areas, and they require no re-treatment over the life of the installation.
Practical Application: Choosing Timber for Outdoor Furniture
When selecting timber for outdoor furniture in Australia, AS 5604 durability class should be the first filter applied. The following guidelines reflect common procurement practice across NSW, VIC and QLD.
Public outdoor use (parks, schools, councils): Class 1 is mandatory for most state and local government procurement. The timber must remain serviceable for a minimum of 25 years without chemical re-treatment.
Covered outdoor areas: Class 2 is generally acceptable where the furniture is protected from direct rain by a pergola, veranda or shade sail. Class 1 remains preferred for longevity.
Fully exposed to rain and dew year-round: Class 1 is the correct specification. No Class 2 or lower species should be used in permanently exposed installations without additional protective coatings.
Auscraft's Premium Hardwood Picnic Table and Heavy Duty Commercial Grade are both manufactured from AS 5604 Class 1 timber, making them suitable for the most demanding outdoor applications.
Ready to order? Request a free quote from our West Gosford NSW workshop. We respond within one business day.
AS 5604 in Council and Government Procurement
AS 5604 is embedded in procurement specifications across all Australian states and territories. Local councils, state government agencies and educational institutions routinely reference the standard in their furniture and playground equipment tenders.
In NSW, VIC and QLD, Class 1 is the standard minimum for outdoor public furniture in unprotected locations. Tender responses from furniture suppliers are expected to include documentation confirming the AS 5604 class of the timber used, typically in the form of a species declaration or timber certification from the supplier's mill.
Specifiers evaluating outdoor furniture for public spaces should request the following from suppliers: the botanical name of the timber species, the AS 5604 class for that species, and whether the timber is heartwood-selected (sapwood of even Class 1 species can have lower natural durability).
Auscraft's Classic Picnic Table is regularly supplied to councils across NSW and QLD under Class 1 specifications. All products are manufactured from heartwood-selected Australian hardwoods.
Ready to order? Request a free quote from our West Gosford NSW workshop. We respond within one business day.
Frequently Asked Questions About AS 5604
What does AS 5604 Class 1 mean?
AS 5604 Class 1 means the timber has been classified as Highly Durable under the Australian Standard for Timber Durability. Class 1 timber has an expected in-ground service life of 25 or more years and an above-ground service life of 40 or more years without chemical treatment. It is the highest durability rating available under the standard.
Is treated pine covered by AS 5604?
No. AS 5604 covers the natural durability of untreated timber only. Chemically treated timber, including CCA-treated pine, is covered by a separate standard called AS 1604. These two standards should not be confused. Treated pine may achieve outdoor suitability through chemical preservation, but its performance is governed by AS 1604, not AS 5604.
Which hardwood species are Class 1 in Australia?
Common Australian Class 1 hardwood species include Spotted Gum (Corymbia citriodora), Ironbark (Eucalyptus sideroxylon), Grey Ironbark, QLD Red Gum (Eucalyptus tereticornis), Jarrah and Tallowwood. Merbau (Intsia bijuga), a tropical import widely used in Australia, also carries Class 1 rating. These species do not require chemical treatment for outdoor use.
Do I need AS 5604 Class 1 for a school picnic table?
Yes, in most cases. Australian schools, particularly those with outdoor furniture in exposed locations, are expected to specify Class 1 timber under state government procurement guidelines. Class 1 ensures the furniture will remain structurally sound and splinter-free for the expected service life without re-treatment. Using Class 3 or Class 4 timber in a school setting would typically not meet duty-of-care requirements.
How does AS 5604 affect my outdoor furniture purchase decision?
AS 5604 gives you an objective, standards-based way to compare timber species for outdoor use. When purchasing outdoor furniture, ask for the AS 5604 class of the timber used. For any furniture that will be left outdoors year-round in Australia, insist on Class 1 or Class 2 as a minimum. Class 1 is strongly preferred for exposed installations. Suppliers who cannot provide this information may be using lower-grade or non-specified timber.
