Ash, Silvertop

Silvertop ash is a large Australian hardwood that is commonly used for general construction and flooring.

Other Names

Coast Ash, Ironbark, Silvertop, Black Ash, Eucalyptus sieberiana

Botanical Name

Eucalyptus sieberi

Common Form
Sawn
Species Type
Hardwood
  • Overview

    • Silvertop ash is a large, moderately durable Australian hardwood that grows in the southern and central coast and tablelands of New South Wales, eastern Victoria and north eastern Tasmania. It is also known as ‘coast ash’ due to its occurrence along the coastal areas of the cooler eastern states.

    Of medium texture, silvertop ash has an interlocked grain and with noticeable growth rings. The heartwood is brown, sometimes pinkish and the sapwood is narrow in appearance. Gum veins, markings from pinhole borers and pencil streaks also distinguish the appearance of silvertop ash.

    Care needs to be taken when drying silvertop ash, because of its proneness to surface checking on the tangential surface. It is also slow to dry.

    Silvertop ash provides good fire resistance, and is one of seven hardwood timber species that was found to be suitable by the Building Commission in Victoria for home construction in bushfire areas (provided it has a thickness greater than 18 mm).

    It is mainly used for general construction, but is also used for flooring, furniture, handles, joinery, fence posts, cases and chemical pulp.

     

    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.
    10.60%

    Radial : Radial shrinkage is perpendicular to the growth rings. It is shrinkage in the direction towards the centre of the tree. Measurement is % value
    5.70%

    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.
    0.36%

    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.
    0.25%

    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:

    F17

    F14

    F11

    F8

    F7

    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:

    850kg/m3

    Unseasoned:

    1100kg/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.
    78

    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.
    137

    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.
    13.2

    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.
    17.3

    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.
    41,6

    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.
    75

    Impact - Unseasoned: Provides the Izod value, which is the energy taken in joules (J) to fracture the timber.
    19.5

    Impact - Seasoned: Provides the Izod value, which is the energy taken in joules (J) to fracture the timber.
    20.3

    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.
    6.7

    Hardness - Seasoned: Refers to the Janka hardness test and is a measure of timber’s resistance to indentation.
    9.7

    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.

    		 Check mark
    (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.

    Not 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.

    >2.2 and <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.
    Bushfire Attack Level (BAL) 12.5, 19 and 29 - All AS 3959 Required Applications
    Appearance

    Silvertop ash has a narrow sapwood, which is not clearly distinguishable from the heartwood. Its heartwood is brown and sometimes pinkish in colour and often features the grain interlocked with growth rings.

    With a medium texture, silvertop ash is also recognisable by the common occurrence of gum veins, the markings of pinhole borers and pencil streaks.

    Common Applications

    Silvertop ash is mainly used as a building timber, such as in timber framing, It is often used for building framework on the south coast and tablelands of NSW. It is strong and reasonably durable, plus it has also been found to provide good fire resistance.

    Other common applications include flooring, furniture and high-end joinery. Silvertop ash is also used for vehicle construction, handles, fence posts, cases and chemical pulp.

    Workability

    A tough, moderately durable timber, silvertop ash is reasonably easy to work. It machines well and can be worked with standard woodworking tools. It is easy enough to split along the rays, and it was for this reason that the pioneers used silvertop ash for roof shakes.

    It accepts most coatings and is excellent for nailing and screwing. Silvertop ash sands well but is inclined to splinter. It is also suitable for steam bending. 

    Silvertop Ash occurs in New South Wales, Victoria and Tasmania
    Silvertop Ash is commonly available throughout Australia, especially in New South Wales, Victoria and Tasmania
    Source of timber
    Native Forest

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