Gum, Yellow

Yellow gum is a medium sized native Australian hardwood valued for its toughness and durability. It is an ideal choice for heavy construction.

Other Names

Blue Gum, White Ironbark, South Australian Blue Gum, Large Fruited Blue Gum, Water Gum

Botanical Name

Eucalyptus leucoxylon

Common Form
Sawn
Species Type

Yellow gum or Eucalyptus leucoxylon is a medium sized hardwood that grows to about twenty metres in height. It is difficult to describe yellow gum as a single tree type, as there are many different sub-species, each with its own appearance and habitat. In general, trees of this species are noted for their long flowering period and attractive bark, which is dark and fibrous at the base of the trunk. The remainder of the trunk is smooth, grey, mottled yellow or white and bluish-grey on the upper trunk and branches.

The overall species has a native range extending from southern NSW through central and western Victoria into most of South Australia, including Kangaroo Island. Yellow gum is suited to most areas except the tropics and adapts to most soils. It is drought and frost tolerant, and moderately fast growing. It also tolerates smog.

Yellow gum timbers are prized for their hardness, durability and impressive structural properties. Its vast range and availability make it an appealing choice for those requiring timber for heavy construction purposes. Common uses include heavy construction as posts, wharfage, bridgework, sleepers and fencing.

The timber is also termite resistant, although the sapwood is prone to lyctid borer. Workability is sacrificed for durability, as the timber is extremely dense and heavy. For this reason, it is not well suited to cabinetry.

Yellow gum timber ranges in colour from yellow to pale brown. Grain is interlocked with a moderately coarse texture and often produces an attractive fiddleback figure.

Yellow gum is often used in gardening as a screen, for windbreaks, and for displays of long-lasting, attractive flowers. It can be used to produce fine honey.

Shrinkage

Very Low Low Medium High Very High

Tangential :

6.30%

Radial :

2.80%

Unit Movement Tangential:

0.32%

Unit Movement Radial:

0.19%

Strength Group

Very High

High

Reasonably High

Medium High

Medium

Reasonably Low

Low

Very Low

Unseasoned:

S1

S2

S3

S4

S5

S6

S7

S8

Seasoned:

SD1

SD2

SD3

SD4

SD5

SD6

SD7

SD8

Stress Grade

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

Unseasoned:

F14

F11

F8

F7

F5

Seasoned:

F14

F11

F8

F7

F5

Density per Standard

Seasoned:

1010kg/m3

Unseasoned:

1200kg/m3

Joint Group

Very High

High

Reasonably High

Medium

Low

Very Low

Unseasoned:

J1

J2

J3

J4

J5

J6

Seasoned:

JD1

JD2

JD3

JD4

JD5

JD6

Colour

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

Mechanical Properties

Modulus of Rupture - Unseasoned:

87

Modulus of Rupture - Seasoned:

111

Modulus of Elasticity - Unseasoned:

11

Modulus of Elasticity - Seasoned:

12

Maximum Crushing Strength - Unseasoned:

44

Maximum Crushing Strength - Seasoned:

67

Impact - Unseasoned:

17

Impact - Seasoned:

9

Toughness - Unseasoned:

Toughness - Seasoned:

Hardness - Unseasoned:

9.1

Hardness - Seasoned:

11.6

Durability

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

In-Ground:

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

Above ground:

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

Marine Borer Resistance:

Lyctid Borer Susceptibility:

Susceptible

Lyctid Borer Susceptibility - Other:

Termite Resistance:

Resistant

Fire Properties

Critical Radiance Flux - Lower:

>2.2 and <4.5

Critical Radiance Flux - Higher:

≥4.5

Smoke Development Rate:

<750
1 - non-combustible 2 - reasonably non-combustible 3 - slightly combustible 4 - combustible

Fire Properties Group
Number:

Average Specific Extinction Area:

<250

Bushfire Resistance:

BAL 12.5 and 19 – All AS3959 required applications
Appearance

The heartwood of the yellow gum is, as its name suggests, yellow to pale brown in colour. It is common for the heartwood to exhibit pink and yellow tints around features. Sapwood is slightly paler and easily distinguished from the heartwood.

Due to the high density of this moderately fast growing timber, yellow gum features an interlocked grain and a somewhat coarse texture. It often produces an attractive fiddleback figure.

Common Applications

Yellow gum timbers are prized for being hard, strong and very durable. This is an ideal timber for structural engineering purposes, including fencing and building. Timber of the Eucalyptus leucoxylon is used for sleepers and poles and is well suited to heavy construction such as wharfage and bridgework.

Yellow gum timber is also ideal for use as fuel as it burns with few sparks and makes excellent coals. However, its density and hardness make it very difficult to split, and it is also tough to ignite.

Workability

Yellow gum is a very heavy, durable timber. It has a high rating in all classifications. Timber of this species dries to about 1000kgs/m3 (66lbs/ft3). The in-ground durability of Yellow gum timber is class 2, as is its above ground durability. Yellow gum heartwood is resistant to termites, but its sapwood is susceptible to lyctid borer.

When timbers are as hard and heavy as yellow gum, they are very hard to work. Cutter angles on planes need to be reduced. Pre-boring for fixings is considered mandatory. The timber can be glued, but it is best to do this immediately after dressing. It sands and polishes to a superb finish and accepts preservative impregnation.

Origin of timber
VIC
Readily Available
VIC
Yellow gum has limited availability in western Victoria extending into southern South Australia.
Source of timber
Native Forest
Image

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.
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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.
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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.

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