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Gum, Mountain Grey

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Mountain grey gum is a medium to tall tree growing up to 65 metres in height on favourable sites. It occurs in the Grampian Ranges and around Cape Otway in Victoria, and on the coastal fall of the southern tablelands of New South Wales.

The wood of this species is a pale brown colour, often with pink or yellow tinges. Sapwood is generally paler, but not always visually distinct from the heartwood. Grain is typically straight and close, with occasional interlocking. Texture is moderately coarse and even, and gum veins are common.

Mountain grey gum timber is moderately durable. Untreated heartwood, although lacking termite-resistance, has an aboveground life expectancy of between 15 and 40 years. Untreated sapwood is susceptible to Lyctid borer attack.

Given the timber’s hardness, mountain grey gum is reasonably easy to work by hand or machine.

Common uses of mountain grey gum timber include bridge and wharf construction, general construction applications such as building framework, wheelwright work, sleepers, paneling and flooring. The timber has potential for furniture, joinery and veneer applications, although care is required in the selection of timber suitably free of gum veins.

 

Appearance

The wood of mountain grey gum is a pale brown colour, often with pink or yellow tinges. Sapwood is generally paler, but not always visually distinct from the heartwood. Grain is typically straight and close, with some interlocking. Texture is moderately coarse and even.

 

Common Applications

Common uses for mountain grey gum timber include general construction applications such as building framework, bridge and wharf construction, wheelwright work, sleepers, paneling and flooring.

 

Common Form

Sawn

Workability

Mountain grey gum is reasonably easy to work, however excessive gum veining can interfere with finishing procedures, and careful selection is required for decorative applications.

 

Origin of Timber

NSW

Readily Available

NSW

Availability - Further Information

Mountain grey gum timber products are commonly available in southern New South Wales and parts of Victoria. Commercial availability is limited in other Australian states.

Availability - Further Information

Native Forest

Shrinkage

Very Low Low Medium High Very High

Tangential :

11.90%

Radial:

5.30%

Unit Movement Tangential:

0.39%

Unit Movement Radial:

0.27%

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:

870kg/m3

Unseasoned:

1150kg/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:

75

Modulus of Rupture - Seasoned:

141

Modulus of Elasticity - Unseasoned:

14

Modulus of Elasticity - Seasoned:

18

Maximum Crushing Strength - Unseasoned:

39

Maximum Crushing Strength - Seasoned:

76

Impact - Unseasoned:

17

Impact - Seasoned:

18

Toughness - Unseasoned:

Medium - 15 - 24 Nm

Toughness - Seasoned:

Medium - 15 - 24 Nm

Hardness - Unseasoned:

7.0

Hardness - Seasoned:

10

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

0 1 2 3 4 5 6 7 8 9 10

EFH Spread-of-Flame Index:

EFH Smoke-Developed Index:

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:

<250

Bushfire Resistance:

BAL 12.5 and 19 – All AS3959 required applications

Retaining Walls (Landscaping)

The natural appeal, strength and versatility of timber makes it an ideal choice for retaining wall landscaping applications.

Retaining wall systems include cantilevered round or sawn timber, mass wall and crib wall construction. Walls up to one metre in height follow a basic design and can usually be constructed using standard proprietary wall systems. An engineer will be required to plan and design walls greater than one metre, including the footings and drainage.

Drainage of retaining walls is a critical factor in influencing the long term stability of the wall and should thus form a significant part of the design and planning process. 

Regular care and maintenance of retaining walls is essential in ensuring the long-term stability and safety of the structure.

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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