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Spotted Gum Hardwood Timber information

Hardwood Timber Properties

Colour:
The heartwood ranges from light brown through to dark brown. Sapwood is usually white in colour and up to 50mm wide.

Grain:
Moderately coarse textured and variable. Gum veins common. The presence of wavy grain can produce an attractive fiddle back figure.

Hardness:
Very hard (rated 1 on a 6 class scale) in relation to resistance to indentation and ease of working with hand tools.

Machining:
Machines well due to its natural greasiness.

Finishing:
Will readily accept paint and polish. Has a lower tannin content than most other eucalyptus and is less likely to cause problematic tannin stains than most other Aussie hardwoods.

Name:
Corymbia maculata & Corymbia citriodora Formerly E. maculata

Hardwood Timber Source

Environment-friendly managed source:
Spotted gum is generally found in dry sclerophyll forests and is not a rainforest species. Sclerophyll forests are forests which include species with drought resisting "hard leaves". Dry sclerophyll forests are sclerophyll forests occurring in drier regions and have an open canopy with a predominantly grassy understorey.

Source: Queensland Department of Environment and Resource Management June 2009
Download document 720KB PDF.

Hardwood Timber Uses

Engineering:
As sawn or round timbers in wharf and bridge construction, railway sleepers, crossarms, poles, piles, mining timbers.

Construction:
As unseasoned timber in general house framing and as seasoned dressed timber in cladding, internal and external flooring, lining and joinery. Also in fencing, landscaping, retaining walls and as structural plywood and hardboard.

Decorative:
Internal quality furniture, outdoor furniture, turnery, joinery, parquetry.

Others:
Tool handles, boat building, coach vehicle and carriage building, agricultural machinery, sporting goods (baseball bats, spring and diving boards, parallel bars), bent work. Spotted gum is the main Australian species for tool handles subject to high impact forces e.g. axe handles.

Its physical properties are well in excess of pines and most non Australian hardwoods. Tabled below is a comparison with Douglas fir and teak.

Hardwood Timber Property Comparison 

Timber Property Ref North American
Douglas Fir (Coastal)
Psendetsaga menziesii
Teak
Tectona grandis
Spotted Gum
Coryumbia citrodora
Density at 12% moisture Kg/m3: 1 560 670 1010
In-ground Durability Class (DIG):
(In-ground contact life expectancy)
1 4
(0-5 Yrs)
2
(15-25 Yrs)
2
(15-25 Yrs)
Above-ground Durability Class (DAG):
(Above-ground life expectancy)
3 4 1 1
Joint Group: 1 J4 (low) J3 J1 (high)
Stress Grade At Structural 2: 2 F8 F7 F17
Termite Resistance: 3 NR R R

Basic Working Stress Properties:
Bending Stress (F'b): 2 8.6 MPa 6.9 MPa 17.0 MPa
Modulus Of Elasticity (E): 2 9100 MPa 7900 MPa 14000 MPa
Tension Stress Parallel (F't): 2 5.2 MPa 4.1 MPa 10.2 MPa
Compression Stress Parallel (F'c): 2 6.6 MPa 5.2 MPa 13.0 MPa
Compression Perp. To Grain (F'p): 2 2.6 MPa 2.1 MPa 5.2 MPa
Janka Hardness: 4 3.2 KN 4.5 KN 11 KN
 

References:

  1. Building Timbers - Technical Pamphlet No 1 - Queensland Forest Service 1991
  2. Australian Standard 1720.1 Timber Structures Code 1988
  3. Construction timbers in Queensland: Properties and specifications for satisfactory performance DPI & F.
  4. Wood in Australia: Types, properties and uses.

Note:
When the strength and durability is the prime consideration and we may mix timber of similar or better properties which include ironbark, tallowwood, and forest red gum. This allows the best use of our species mix. When a uniform colour is required species are not mixed.

Sizes:
Australian hardwood is cut in multiples of 25 mm with the exception of 38 mm. The table below gives the sizes which can be expected in its different formats. For larger quantities we can cut to a fractional size.

Spotted Gum can be dressed into any profile you require within the table limitations below, e.g from a piece of 150 x 50 mm we can produce a seasoned sill with a maximum size of 136 x 42 mm.

Standard Sizes Of Australian Hardwoods 

  SAWING TOLERANCE GREEN SIZED GREEN  DAR* DRESSED SEASONED
25 +/- 3 mm 22 20 19
38 +/- 3 mm 35 33 31
50 +/- 3 mm 47 45 42
75 +/- 3 mm 72 70 66
100 +/- 3 mm 97 95 90
125 +/- 3 mm 122 120 113
150 +/- 3 mm 147 145 136
175 +/- 3 mm 172 170 160
200 +/- 3 mm 197 195 183

*DAR - Dressed All Round

Notes:
Lengths (in multiple of 300 mm) to 4.8 metres are readily available and available up to 7.5 metres in limited quantities. Kiln drying is impractical over 50 mm thick. Larger sizes are frequently vertical laminated. Kiln dried timber is not required or recommended for bridge or boardwalk construction.

SIZES OF  STANDARD SEASONED PRODUCTS - MEASUREMENTS ARE COVER

GREEN SIZE DECKING T&G FLOORING CLADDING
70X25 65X19 60X19
100X25 89X19 83X19 78X19
150X25 136X19 NOT RECOMMENDED 126X19
 

(The above information is largely drawn from Timber Queensland and NAFI publications.)

 

Resource: outdoorstructures.com.au/spotted_gum_hardwood.php Printed: 2019-02-17.