Spotted Gum (Corymbia Maculata)

Spotted Gum is a premium Australian hardwood that is used widely in structural, exterior and internal applications.

Spotted Gum is one of Australia’s premium native hardwoods with a striking appearance and a high degree of natural durability and strength, making it an ideal timber for a variety of structural, exterior and interior applications. Architects and designers throughout the world value Spotted Gum timbers for their back-sawn grain structure, attractive markings and vibrant colour palette.

Spotted Gum is the common name for four species that grow along the east coast of Australia, from northeast Victoria to the northern tablelands of Queensland, with some occurrence in western areas of southern Queensland. Sawn timber from these species is generally available throughout Australia. These species have straight, slender trunks with smooth bark that is shed in patches, giving the trees their characteristic spotted appearance.

The species referred to as Spotted Gum vary in appearance but not in durability class or other properties. The heartwood ranges from light brown through to dark red-brown hues. Sapwood is usually white to light brown in colour. The presence of a wavy grain can produce an attractive fiddle-back figure. The wood has a slightly greasy feel, a characteristic that aids machining and boring. Spotted Gum components that are 18mm thick or greater do not require fire retardant treatment for use in construction in bush-fire prone areas.

Spotted Gum is used 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. Spotted Gum is also used in the manufacture of veneer and plywood. Other applications include boatbuilding, tool and implement handles, polo sticks and diving boards. Compared to other Australian hardwoods, Spotted Gum is a minimal staining timber as it is less prone to bleed-through of tannins than other species. Spotted Gum is also a good timber for carving and woodturning.

SHRINKAGE

  Very Low Low Medium High Very High
This is the measure of the percentage reduction in dimension from the unseasoned to 12% moisture content condition.
Tangential This is the measure of the percentage reduction
6.1
Radial
3-4
Unit Movement
0.38%

STRENGTH GROUPS

  Very High High Reasonably High Medium High Medium Reasonably Low Low Very Low
Uneasoned
S1
S2
S3
S4
S5
S6
S7
Seasoned
SD1
SD2
S3
SD4
SD5
SD6
SD7
SD8

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
F34
F27
F22
F17
F14

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.

Unseasoned 1150kg/m3
Seasoned 990kg/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
Seasoned
JD1
JD2
JD3
JD4
JD5
JD6

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
Shade
 

MECHANICAL PROPERTIES

Modulus of Rupture – Unseasoned
99
Modulus of Rupture – Seasoned
150
Modulus of Elasticity – Unseasoned
18
Modulus of Elasticity – Seasoned
23
Maximum Crushing Strength – Unseasoned
50
Maximum Crushing Strength – Seasoned
75
Impact – Unseasoned
20
Impact – Seasoned
24
Toughness – Unseasoned
High – 25 Nm and above
Toughness – Seasoned
High – 25 Nm and above
Hardness – Unseasoned
8.0
Hardness – Seasoned
11
 
 

DURABILITY

  Low Moderate Reasonably High High
 
(0-5 years)
(5-15 years)
(15-25 years)
(> 25 years)
In Ground  
 
 
(0-7 years)
(7-15 years)
(15-40 years)
(>40 years)
Above Ground    
  (0-20 years, usually <5) (21-40 years) (41-64 years) (>65 years)
Marine Borer Resistance
 
 
Lyctid Borer Susceptibility
Susceptible
Termite Resistance
Resistant

FIRE PROPERTIES

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
EFH Ignitability
                     
             
                                       
EFH Spread of Flame Index
1
2
3
4
5
6
7
8
9
10
     
   
           
                                       
EFH Smoke Developed Index
1
2
3
4
5
6
7
8
9
10
   
           
                                       
Critical Radiance Flux – Lower
>2.2 and <4.5kWm 2
Critical Radiance Flux – Higher
>4.5kWm 2
Smoke Development Rating
<750
Fire Properties Group Number
1 – Non Combustible
2 – reasonably non combustible
3 – slightly combustible
4 – combustible
                   
         
                                       
Group Number – Other
For Plywood – Fire Properties – EFH Spread-of-flame Index: 7
Average Specific Extinction Area
<250
Bushfire Resistance
BAL 12.5, 19 and 29 – All AS3959 required applications
                                         

Botanical Name:

Corymbia Maculata

Common Name:

Spotted Gum

AKA:

Lemon-scented Gum, Spotted Irongum, Eucalyptus maculata, Corymbia citriodora, Eucalyptus citriodora, Corymbia henryi, Eucalyptus henryi

Type:

Hardwood

Appearance

Spotted Gum timbers are available in a range of colours depending on the location of the source forest. The heartwood ranges from light brown through definite browns to deep red-brown hues. Sapwood is white to light brown in colour and can be up to 50mm wide. Spotted Gum is a moderately coarse and uneven textured wood with some timbers having the additional feature of a wavy grain, giving rise to an attractive fiddleback figure.

Common Applications

Spotted Gum has a long history of usage in engineering applications such as wharf and bridge construction, railway sleepers, cross-arms and mining timbers. It is used for a variety of applications, including structural building members, such as posts and poles, and for framing, flooring, lining, decking and cladding. It is also used in boatbuilding and is the primary Australian timber used for the handles of tools and implements that are subject to high impact forces. Spotted Gum is a suitable carving and woodturning timber and is used in the manufacture of both indoor and outdoor furniture. Outdoor furniture in Spotted Gum has consistently won industry awards in Australia and is exported to a range of destinations around the world.

Common Form

Sawn, Veneer

Workability

Spotted Gum machines well due to its natural greasiness and there is no difficulty using the timber with standard fittings and fastenings. As with most high-density species, machining and surface preparation should be done immediately before gluing. Spotted Gum readily accepts paint, stains and polish. It has a lower tannin content than most other eucalypts, therefore staining of paintwork or brickwork as a result of water running over unpainted timber surfaces is less likely to occur.

Architectural Roof Trusses

Architectural timber roof trusses create strong visual impact. Often used as part of ‘cathedral ceiling’ systems, timber can be specified light or heavy to suit the chosen theme and style. On finish, they can be left natural or may be oiled, stained, painted or highly decorated. Choice is limited only by individual style and design preferences.

Decking

Timber decking creates spaces that are functional, practical and aesthetically pleasing. With the right design and care a timber deck will make a valuable addition to any home or business, creating an outdoor living space that will be enjoyed for years to come.

Doors

Timber is one of the most popular and superior material choices for both internal and external doors. Whether manufactured from solid or engineered timber, there are many stylish and practical options that won’t compromise on strength and structural performance. A distinctive timber door can also create visual impact, adding value to any commercial or domestic building.

Exterior Stairs

For outdoor applications, timber is one of the leading material choices. Timber use in external staircase applications creates structures of strength and durability, sheathed in a natural beauty that blends seamlessly with the outdoor environment.

External Cladding

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.

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.

Framing

Since people began building simple shelters, wooden framing has played an important role in shaping structures of many kinds. One of the most popular types of wooden framing is known as lightweight timber construction.

Interior Stairs

Timber should be the material of choice for designers seeking internal staircases of strength, beauty and durability. The construction procedure described here applies to most general type stairs of either conventional or contemporary construction.

Internal Panelling

Timber paneling creates interiors as warm as they are stylish. Commonly utilising an MDF or plywood substrate, internal timber paneling is natural and versatile and comes as either solid natural timber panels or as sheets of engineered wood products

Structural Timber Posts

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.

Timber Joinery Products

Timber joinery products offer a classic, unique and stylish touch to any interior design.

Timber Mouldings

Mouldings are extremely versatile and durable, enhancing the aesthetics of any interior and functioning as the icing on the cake for designs with a focus on beauty and splendour.

Timber 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. This application guide provides a comprehensive overview of the process of using timber in the specification, fabrication and erection of portal frame structures.