Mahogany, White

White mahogany is a premium Australian hardwood used for structural, interior and exterior applications.

Other Names

Yellow Stringybark (Qld), White Stringybark, Narrow-leaved White Mahogany, Eucalyptus Umbra, Eucalyptus tenuipes

Botanical Name

Eucalyptus acmenoides

Common Form
Sawn
Species Type
Hardwood
  • Overview

    • White mahogany is one of Australia's premium native hardwoods with a high degree of natural durability and strength, making it an ideal timber for a variety of structural, exterior and interior applications. White mahogany is the common name for four species that grow along the east coast of Australia, from mid-New South Wales to northern Queensland, with isolated pockets north of the Queensland tablelands. Sawn timbers from these species are readily available across Australia.

    They have straight, slender trunks with rough, fibrous bark that is shed in strips, giving the trees their characteristic stringy appearance and resulting in the common local names of yellow or white stringybark.

    The species varies in appearance but not in durability class or other properties. The heartwood is light brown to yellow brown in colour. The sapwood is usually creamy brown and is uniformly lighter than the heartwood. White mahogany wood has a slightly greasy feel, a characteristic that aids machining and boring.

    It is termite resistant and the sapwood can be easily treated with preservatives. The heartwood is too dense to accept readily available commercial preservation processes.

    The wood is used as a sawn timber in engineering applications such as wharf and bridge construction, railway sleepers, cross-arms and mining timbers. It is suitable for a range of building applications, such as posts and poles, framing, flooring, lining, decking and cladding. White mahogany is also used in the manufacture of veneer and plywood. Other applications include boatbuilding, coach and carriage building, and agricultural machinery.

    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.
    5.40%

    Radial : Radial shrinkage is perpendicular to the growth rings. It is shrinkage in the direction towards the centre of the tree. Measurement is % value
    2.80%

    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.

    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.

    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:

    F27

    F17

    F14

    F11

    F8

    Seasoned:

    F27

    F22

    F17

    F14

    F11

    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:

    950kg/m3

    Unseasoned:

    1150kg/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.
    101

    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.
    130

    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.
    16

    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.
    17

    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.
    49

    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.
    76

    Impact - Unseasoned: Provides the Izod value, which is the energy taken in joules (J) to fracture the timber.
    17

    Impact - Seasoned: Provides the Izod value, which is the energy taken in joules (J) to fracture the timber.
    14

    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.
    Medium - 15 - 24 Nm

    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.
    Medium - 15 - 24 Nm

    Hardness - Unseasoned: Refers to the Janka hardness test and is a measure of timber’s resistance to indentation.
    8.9

    Hardness - Seasoned: Refers to the Janka hardness test and is a measure of timber’s resistance to indentation.
    10

    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.
    1 - non-combustible 2 - reasonably non-combustible 3 - slightly combustible 4 - combustible

    Fire Properties Group
    Number:

    Group Number - Other:
    3 if used on MDF or particleboard ≥12mm; veneer thickness 0.6-0.85mm

    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

    White mahogany timbers are available in a narrow range of colours. The heartwood is light brown to yellow brown in colour and has a similar appearance to tallowwood. The sapwood is usually creamy brown, clearly lighter in colour than the heartwood and generally less than 20mm wide. A mostly uniform and medium textured wood, white mahogany can sometimes have an interlocked grain. It can also feature distinctive markings caused by moth grub holes and occasional gum veining. It has a slightly greasy feel, although not as greasy as the similarly coloured tallowwood or spotted gum.

    Common Applications

    White mahogany is often used for above ground framing and decking in both protected and unprotected contexts. It can also be used for heavy construction work, from sawn and round timber in wharf and bridge construction to railway sleepers, cross arms, poles, piles. and as mining timbers. It is employed in general house framing, as cladding, linings, joinery, fencing, landscaping and in retaining walls. The species is also suitable for use in structural plywood, boat building (keel and framing components, planking), coach, vehicle and carriage building and agricultural machinery. It is often used in internal and external flooring as its hardness means it does not easily dent, and is also frequently used in outdoor furniture due to its durability.

    Workability

    White mahogany machines well due to its natural greasiness, and there is no difficulty using it with standard fittings and fastenings. Due to its hardness, the timber is not easily worked with hand tools. As with other high-density species, machining and surface preparation should be done immediately before gluing. Easily painted, stained, and polished, the sapwood readily accepts preservatives but the density of the hardwood makes it resistant to current commercial preservative compounds.

    Origin of timber
    NSW
    Readily Available
    NSW
    White mahogany is an important commercial species in NSW and Queensland.
    Source of timber
    Native Forest
    a large room with rows of chairs

    Portal Frames

    For buildings that require large spans and column free interiors, timber portal frames provide one of the most aesthetically pleasing solutions. Utilising modern engineering technology, portal frame design transforms timber into a highly effective, efficient and economical structural product.
    a wooden fenced hillside with plants and a fenced yard

    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.
    a close-up of a building

    Cladding, External

    The natural appeal, versatility and strength of timber makes it the superior choice for external cladding. Through specification, planning, design and finishing processes, timber cladding not only creates a building of superior strength, acoustic and thermal performance but also creates a place of beauty, style and natural appeal.
    a wooden structure in a building

    Shear walls

    Lateral loads such as wind or earthquake on framed timber buildings - either post and beam or stud and joist - need to be resisted and shear walls and diaphragms offer an effective and economical solution.
    a room with tables and chairs

    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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