Ironbark, Grey

Grey ironbark is a premium native Australian hardwood with a wide range of applications from industrial construction to house framing, flooring and sporting goods.

Other Names

White Ironbark, Eucalyptus drepanophylla, Eucalyptus siderophloia, Eucalyptus decepta

Botanical Name

Eucalyptus paniculata

Common Form
Sawn
Species Type
Hardwood
  • Overview

    • Grey ironbark is a premium native hardwood that has been well regarded as a high quality timber in Australia throughout human history. Indigenous Australians use it to make spear throwers and boil its bark for treating sores.

    It is a particularly hard, strong and durable timber, with a broad range of applications, due to its resistance to lyctid borers and termites.

    The grey ironbark is a medium sized tree of 30 to 50m with a stem diameter of 1.5m. The bark is hard, coarse, with deep furrows and ridges, ranging from dark brown to black in colour and grows even on the small branches.

    E. drepanophylla is found from northern New South Wales to Bundaberg, Queensland. It is also found in scattered patches as far north as the Atherton Tableland. E. paniculata is found in New South Wales only from Bega to Coffs Harbour.

    A very heavy timber, at 1120 kilograms per cubic metre, grey ironbark is dense and can be difficult to work. Dressed surfaces take on a steely sheen.

    The timber's appearance ranges from reddish to dark brown heartwood. The sapwood is lighter in colour and is 20mm thick on average. Grain is usually tight and straight and no distinctive figure is encountered.

    Both sawn and round grey ironbark timber have a wide range of applications. Engineering uses include railway sleepers, construction, poles and cross-arms, and bridge construction. Unseasoned timber is used in house framing, while dressed timber can be employed for both internal and external use. It has also been used in boat, coach, vehicle and carriage building and to create sporting goods.  

    Shrinkage

    Very Low Low Medium High Very High
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    Tangential : Provides a simplified rating for tangential shrinkage. This is the measure of the percentage reduction in dimension from the unseasoned to 12% moisture content condition.
    7.50%

    Radial : Radial shrinkage is perpendicular to the growth rings. It is shrinkage in the direction towards the centre of the tree. Measurement is % value
    4.70%

    Unit Movement Tangential: This is the percentage of dimensional change for each 1% moisture content change between about 3% moisture content and the fibre saturation point for the particular species.
    0.39%

    Unit Movement Radial: This is the percentage of dimensional change for each 1% moisture content change between about 3% moisture content and the fibre saturation point for the particular species.
    0.31%

    Strength Group Strength groups are given for unseasoned (S1-S7) and seasoned (SD1-SD8) timber in accordance with AS 2878. S1 and SD1 yield the highest strength and stiffness whereas S7 and SD8 yield the lowest.

    Very High

    High

    Reasonably High

    Medium High

    Medium

    Reasonably Low

    Low

    Very Low

    Unseasoned:

    S1

    S2

    S3

    S4

    S5

    S6

    S7

    S8
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    Seasoned:

    SD1

    SD2

    SD3

    SD4

    SD5

    SD6

    SD7

    SD8
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    Stress Grade A stress grade is defined in AS 1720 as the classification of timber for structural purposes by means of either visual or machine grading. The stress grade indicates the basic working stresses and stiffnesses to be used for structural design purposes. Measured in MPa.

    Structural
    No. 1    		 Structural
    No. 2    		 Structural
    No. 3    		 Structural
    No. 4    		 Structural
    No. 5

    Unseasoned:

    F22

    F22

    F17

    F14

    F11

    Seasoned:

    F34

    F34

    F27

    F22

    F17

    Density per Standard Seasoned density is based on moisture content of 12%. Unseasoned density is an approximation as it depends on the moisture content at the time of measurement. Measured kg/m3.

    Seasoned:

    1106kg/m3

    Unseasoned:

    1170kg/m3

    Joint Group The joint group is a classification of the strength of a species in joint design. The values are from 1 (very high strength) to 6 (very low strength).

    Very High

    High

    Reasonably High

    Medium

    Low

    Very Low

    Unseasoned:

    J1

    J2

    J3

    J4

    J5

    J6
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    Seasoned:

    JD1

    JD2

    JD3

    JD4

    JD5

    JD6
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    Colour The colour of seasoned heartwood can vary between species and often within a species. The information provided should be used as a general guide only. In most cases, the colour of sapwood is either a lighter shade of the heartwood or a white/cream colour.

      White, yellow, pale straw to light brown Pink to pink brown Light to dark red Brown, chocolate, mottled or streaky
       
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    Mechanical Properties

    Modulus of Rupture - Unseasoned: This property is a measure of maximum stress which timber can momentarily sustain when loaded slowly and continuously as a beam. Measured in MPa.
    121

    Modulus of Rupture - Seasoned: This property is a measure of maximum stress which timber can momentarily sustain when loaded slowly and continuously as a beam. Measured in MPa.
    185

    Modulus of Elasticity - Unseasoned: This property is of importance in determining the deflection of a beam under load — the greater the stiffness, the less the deflection. Measured in GPa.
    19

    Modulus of Elasticity - Seasoned: This property is of importance in determining the deflection of a beam under load — the greater the stiffness, the less the deflection. Measured in GPa.
    23

    Maximum Crushing Strength - Unseasoned:

    Also referred to as compression strength. This property measures the ability of the timber to withstand loads applied on the end grain. Measured in MPa.
    63

    Maximum Crushing Strength - Seasoned: Also referred to as compression strength. This property measures the ability of the timber to withstand loads applied on the end grain. Measured in MPa.
    97

    Impact - Unseasoned: Provides the Izod value, which is the energy taken in joules (J) to fracture the timber.
    27

    Impact - Seasoned: Provides the Izod value, which is the energy taken in joules (J) to fracture the timber.
    25

    Toughness - Unseasoned: This is a measure of timber’s ability to resist shocks and blows, and is synonymous with impact strength. It is measured in Nm.
    High - 25 Nm and above

    Toughness - Seasoned: This is a measure of timber’s ability to resist shocks and blows, and is synonymous with impact strength. It is measured in Nm.
    High - 25 Nm and above

    Hardness - Unseasoned: Refers to the Janka hardness test and is a measure of timber’s resistance to indentation.
    11

    Hardness - Seasoned: Refers to the Janka hardness test and is a measure of timber’s resistance to indentation.
    16

    Durability

    Low Moderate Reasonably High High
    (0 - 5 yrs) (5 - 15 yrs) (15 - 25 yrs) (more than 25 yrs)

    In-Ground: Durability is defined as the inherent resistance of a timber species to decay, or to insect or marine borer attack. All references to durability refer to the heartwood only. A scale of low to high (durability class 4 = low; 1 = high) has been adapted for above and in-ground durability.

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    (0 - 7 yrs) (7 - 15 yrs) (15 - 40 yrs) (More than 40 yrs)

    Above ground: Durability is defined as the inherent resistance of a timber species to decay, or to insect or marine borer attack. All references to durability refer to the heartwood only. A scale of low to high (durability class 4 = low; 1 = high) has been adapted for above and in-ground durability.

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    (0 - 20 yrs, usually < 5) (21 - 40 yrs) (41 - 64 yrs) (More than 60 yrs)

    Marine Borer Resistance: Indicates whether a species is resistant (R) or not resistant (NR) to marine borer attack.

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    Lyctid Borer Susceptibility: Indicates whether a species is susceptible (S) or not susceptible (NS) to lyctid borer attack.

    Not Susceptible

    Lyctid Borer Susceptibility - Other:

    Termite Resistance: Indicates whether a species is resistant (R) or not resistant (NR) to termites.

    Resistant

    Fire Properties

    0 1 2 3 4 5 6 7 8 9 10

    EFH Spread-of-Flame Index: This is a material's propensity to burn rapidly and spread flames based on a scale of 0 to 10 where 0 means that the materials will not cause flames to reach the ceiling and 10 indicates that the material could be expected to cause flames to reach the ceiling of a room within 10 seconds of ignition.

    EFH Smoke-Developed Index:This is a measure of the concentration (measured by optical density) of smoke a material emits as it burns. It is based on an arbitrary scale of 0 to 10. The higher the index, the greater the hazard from smoke is likely to be.

    Critical Radiance Flux - Lower: This measures the radiant (heat) energy required to sustain burning. It is used in Australia to regulate floor coverings. The requirements are set out in BCA Specification C1.10a, providing CRF values for floor coverings based on Class of building, the location within the building (general use or use in fire isolated exits) and whether or not the building is sprinkler protected or not. CRF is measured in kW/m2.

    >2.2 and <4.5

    Critical Radiance Flux - Higher: This measures the radiant (heat) energy required to sustain burning. It is used in Australia to regulate floor coverings. The requirements are set out in BCA Specification C1.10a, providing CRF values for floor coverings based on Class of building, the location within the building (general use or use in fire isolated exits) and whether or not the building is sprinkler protected or not. CRF is measured in kW/m2.

    ≥4.5

    Smoke Development Rate: This is the speed at which smoke increases as determined by testing flooring materials in accordance with AS ISO 9239.1. The rate is expressed in terms of percent/minutes. For buildings not protected with a sprinkler system, a maximum smoke development rate of 750 percent/minute applies.
    <750
    1 - non-combustible 2 - reasonably non-combustible 3 - slightly combustible 4 - combustible

    Fire Properties Group
    Number:

    Average Specific Extinction Area: This value is determined by the volume of smoke measured over the mass loss of the tested sample per test carried out in accordance with ‘Cone Calorimeter Test’ AS/NZS 3837. It is measured in units of m2/kg.
    <250

    Bushfire Resistance: Naturally bushfire-resisting timbers are those with inherent bushfire-resisting properties. Some species have been tested and a number are in the process of being tested and are measured by Bushfire Attack level (BAL). BAL -12.5: Ember attack, BAL – 19: Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 12.5 and 19 kWm3, BAL – 29: Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 19 and 29 kWm3.
    BAL 12.5 and 19 – All AS3959 required applications
    Appearance

    Grey ironbark sapwood is almost white, making it highly distinct from the heartwood, that ranges from light grey or light chocolate with occasional darker reds and browns. The texture is moderately coarse and even, and the grain usually straight, and only occasionally interlocked. Grey Ironbark may have regional variations in colour, with some having black narrow to broad streaks running through the timber.

    Common Applications

    Due to its class 1 strength and durability ratings, grey ironbark is commonly used in engineering applications as a sawn and round timber. It can be specified for wharf and bridge construction, railway sleepers, cross arms, poles, piles and mining timbers.

    The unseasoned timber is excellent for general house framing, while seasoned and dressed grey ironbark timber is used for cladding, internal and external flooring, linings and joinery. It is also ideal for fencing, landscaping and retaining walls.

    The timber's versatility extends to boat building (keel and framing components, planking), including reputed use in the hulls of early ice-breaker ships. Coach, vehicle and carriage building, agricultural machinery, mallet heads, mauls and bearings, sporting goods (croquet mallets, parallel bars) and bowling ninepins have all been made from grey ironbark.

    Workability

    Grey ironbark has been employed for decorative purposes such as in outdoor furniture, turning and joinery, although its density makes it hard to work in applications requiring fine detail.

    It is slow drying and should be handled carefully to avoid surface checking.

    Origin of timber
    NSW
    Readily Available
    NSW
    Grey Ironbark is common to coastal regions of NSW and in southern Queensland. E paniculata is the most common commercial species of Ironbark timber. It is not generally available in a range of sizes, but can be supplied to order. Large sizes in particular are commonly ordered for structural uses, so it is more readily available in this form
    a kitchen with wooden cabinets and a countertop

    Joinery

    Timber joinery offers a classic, stylish touch to any interior or exterior space.
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    Decking

    Timber decking creates spaces that are functional, practical and aesthetically pleasing. With the right design and care a timber deck will make a valuable addition to any home or business, creating an outdoor living space that will be enjoyed for years to come.
    a wood fence with trees in the background

    Fencing

    When it comes to fencing, timber is a natural choice. A material that is durable, strong and reliable it compliments almost every outdoor landscape and environment. Clear specification, detailed installation and appropriate maintenance will ensure a timber fence provides a natural and lasting property boundary and back drop for years to come.
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    Mouldings

    Mouldings are extremely versatile and durable, enhancing the aesthetics of any interior and functioning as the icing on the cake for designs with a focus on beauty and splendour.
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    Retaining Walls (Landscaping)

    When it comes to retaining wall, landscape design and construction, timber is the natural choice. A material that is durable, sturdy and reliable, it has natural aesthetics that help it blend seamlessly with the outdoors. Careful consideration during the specification and design process will facilitate the creation of a long lasting, durable and beautiful timber retaining wall that will complement its surrounding landscape for years to come.
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    Structural Timber Poles

    Timber poles are utilised in structural construction to provide support for gravity loads and resistance against lateral forces. Not only serving a structural function, timber poles provide many aesthetic benefits, with their use in construction often complementing architectural designs aimed at harmonisation with the natural environment.
    a room with benches and paintings on the wall

    Flooring

    The warmth, strength and natural beauty of timber flooring is enduringly popular in a wide variety of domestic, commercial and industrial applications.

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