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Gum, Southern Blue

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Native to the coastal sclerophyll forests of eastern Tasmania, southern blue gum is the world's most widely planted eucalypt species. It is the preferred tree species in plantations throughout Australia. Originally forested for wood chips, pulp and paper fibre, some of the larger plantation trees have been used to produce both timber furniture and flooring material.

The colour of southern blue gum timber ranges from pale straw to brown, often with blue, green or grey tinges. Regrowth material can exhibit shades of pink. Sapwood is somewhat paler than the heartwood, but not always clearly demarcated. Growth rings are prominent on end sections. Grain is often interlocked with a medium and relatively even texture. Timber produced from plantations often exhibits areas of pinhole.

Southern blue gum is a moderately durable timber. It is not termite-resistant and untreated sapwood is susceptible to Lyctid borer attack.

Although very hard, the timber is relatively easy to work, fix and dress.

Due to its density, seasoning requires care in order to minimise checking of tangential surfaces. Southern blue gum blunts cutting edges but good results can be achieved with careful working and the use of correct machinery. The timber can be worked to a smooth and resilient surface that readily accepts most standard finishes. Southern blue gum can be difficult to drill, but holes are usually very clean and to size. Seasoned material can be difficult to nail and utmost care is required when gluing. Southern blue gum is suitable for steam bending if carefully selected for straightness of grain.

Suggested applications of southern blue gum include flooring, joinery, furniture and general construction. The hardness and brightness of this timber makes it an ideal flooring material for indoor sports centres and other venues. Other applications include wagon building, framing, boat building, handles, piles, posts, sleepers, paving blocks, spokes, wheel rims and shafts.

Appearance

Southern blue gum ranges in colour from pale straw to brown, often with blue, green or grey tones. Regrowth material can exhibit shades of pink, while timber produced from plantation will often carry areas of pinhole. The sapwood is paler than the heartwood, but not always clearly demarcated. Grain is often interlocked, with a medium and relatively even texture. Growth rings are prominent on end sections.

Common Applications

Common applications of southern blue gum include flooring, joinery, furniture and general construction. The hardness and brightness of this timber makes it an ideal flooring material for indoor sports centres and other venues. Other applications include wagon building, framing, boatbuilding, handles, piles, posts, sleepers, paving blocks, spokes, felloes and shafts.

Common Form

Sawn

Workability

Although very hard, the timber is easy to work, fix and dress. Considerable collapse can occur if not carefully seasoned. Southern blue gum is suitable for steam bending if carefully selected for straightness of grain.

Origin of Timber

VIC

Readily Available

NSW

Availability - Further Information

Southern blue gum products are commercially available throughout southeast Australia.

Availability - Further Information

Native Forest

Shrinkage

Very Low Low Medium High Very High

Tangential :

14.40%

Radial:

6.90%

Unit Movement Tangential:

0.39%

Unit Movement Radial:

0.26%

Strength Group

Very High

High

Reasonably High

Medium High

Medium

Reasonably Low

Low

Very Low

Unseasoned:

S1

S2

S3

S4

S5

S6

S7

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:

F17

F14

F11

F8

F7

Seasoned:

F34

F27

F22

F17

F14

Density per Standard

Seasoned:

970kg/m3

Unseasoned:

1140kg/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:

84

Modulus of Rupture - Seasoned:

146

Modulus of Elasticity - Unseasoned:

15

Modulus of Elasticity - Seasoned:

20

Maximum Crushing Strength - Unseasoned:

43

Maximum Crushing Strength - Seasoned:

83

Impact - Unseasoned:

20

Impact - Seasoned:

27

Toughness - Unseasoned:

Medium - 15 - 24 Nm

Toughness - Seasoned:

High - 25 Nm and above

Hardness - Unseasoned:

7.3

Hardness - Seasoned:

12

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:

Not 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

Joinery

Timber joinery products offer a classic, unique and stylish touch to any interior or exterior design. The products are produced for a variety of internal applications including door and window frames, cabinetry, skirtings, mouldings and architraves. When looking to the outdoors, joinery products range from decorative eaves and posts to eye-catching railings.

Many timber species are suitable for joinery products and care should be taken in selecting the perfect timber for the particular product and its intended finish. Rare and exotic species such as Teak and Rosewood can generate pieces of outstanding beauty but material cost and availability are also important considerations.

Commercially available species like Tasmanian oak, Australian cypress, spotted gum and the like, often make the more practical choice, with the added benefit that they can be easily matched with other timber products within the building, like flooring.

Solid timber for joinery products is generally supplied as ‘clear finish grade' but ‘paint grade' options are available and these are usually comprised of a composite material like MDF or glulam.

A large number of specialist suppliers and producers offer the consumer extensive choice of profiles for all of the most common and popular joinery products. Choice is in many cases, limited only by imagination.

Cabinetry is often associated with joinery and most typically includes, cupboards, benches and other similar ‘built in' furniture. Like joinery, cabinetry is generally specified as either paint or clear finish grade and naturally for clear finish grade timbers, appearance and surface finish are critical in achieving a successful application.

 

Flooring

Whether for structural or finished flooring applications, timber offers durability, versatility and adaptability. The warmth, strength and natural beauty of timber flooring has proved enduringly popular in a wide variety of interior settings.

Timber flooring is a timeless product, offering a warmth and natural beauty largely unmatched by other flooring options. This article provides an overview of the installation of solid timber strip flooring over bearers and joists, timber based sheet flooring products and concrete slabs. Timber flooring is typically supplied as either solid timber or laminated wood products, made from layers of bonded timber. It fits together with a tongue and groove joint and once in place, is sanded and finished. There is a wide variety of species to select flooring from and the right species for a given application will be dependent on numerous factors. Information relating to species selection, environmental assessment, finish selection and recommended maintenance routines are all provided in this section.

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