Spotted Gum — Corymbia maculata
Australia's premier structural and feature hardwood. Class 1 above-ground durability under AS 5604, top-tier Strength Group SD2 and Joint Group JD1 seasoned, with the distinctive figured grain customers ask for by name. Native to the east coast from northeast Victoria to the northern tablelands of Queensland.
Spotted Gum products
From pre-assembled batten screens to commercial wharf decking, joinery timber and structural framing — all in the same Class 1 above-ground hardwood.
Technical ReferenceSummary
Spotted Gum is one of the most widely specified Australian hardwoods. Three closely related Corymbia species are sold under the single trade name — C. maculata, C. citriodora, and C. henryi — and share equivalent classifications under AS 5604 and AS 1720. The commercial range runs along the east coast from northeast Victoria through New South Wales to the northern tablelands of Queensland.
Its heartwood is rated Class 1 — Very Durable above ground under AS 5604, the highest rating on the Australian four-class natural durability scale. Combined with top-tier classifications on every other Australian Standards measure — Strength Group SD2 seasoned, Joint Group JD1 seasoned — very high density (990 kg/m³ air-dry), high stress grades (F27 unseasoned / F34 seasoned typical), and the distinctive figured grain customers ask for by name, this makes Spotted Gum the default specification for premium exterior cladding, decking, flooring and structural framing throughout Australia.
Class 1 of 4
Character & Appearance
Heartwood ranges from light brown through to dark red-brown hues, often with golden or chocolate notes that warm with UV exposure. The sapwood is usually white to light brown and visually distinct from the heartwood — it is also susceptible to Lyctus borer attack and must be excluded from finished applications or specified Lyctus-immune.
Grain is the defining character. Spotted Gum is known for wavy, interlocked grain that produces the strong "fiddleback" figure prized in flooring and feature cladding. The texture is moderately coarse and uneven. Freshly machined timber carries a clean, faintly lemon-citrus fragrance (most pronounced in C. citriodora). The species is rated 10.1 kN Janka hardness (seasoned) — among the harder commercial hardwoods on the Australian market — and is naturally resistant to termite attack, an additional benefit for exterior structural and decking applications.
Species & General Properties
Mechanical & Physical Properties
| Property | Unseasoned | Seasoned |
|---|---|---|
| Density | 1,180 kg/m³ | 990 kg/m³ |
| Janka hardness | 8.8 kN | 10.1 kN |
| Modulus of rupture (bending) | 98 MPa | 142 MPa |
| Modulus of elasticity | 16 GPa | 19 GPa |
| Maximum crushing strength | 53 MPa | 76 MPa |
| Strength Group | S2 | SD2 |
| Stress Grade (typical) | F27 | F34 |
| Joint Group | J1 | JD1 |
| Shrinkage (Total) | Value |
|---|---|
| Tangential shrinkage | 6.10 % |
| Radial shrinkage | 4.30 % |
Recommended Applications
Spotted Gum's combination of Class 1 above-ground durability, strong Strength Group (SD2 seasoned), top-tier Joint Group (JD1 seasoned), high density and natural termite resistance makes it Australia's default specification for premium structural and exterior hardwood applications.
Specification Notes
- The Class 1 above-ground durability rating applies to heartwood only. Sapwood is susceptible to Lyctus borer and is not naturally durable; specify Lyctus-immune or exclude sapwood from finished applications.
- Three Corymbia species — C. maculata, C. citriodora and C. henryi — are commercially sold as "Spotted Gum" and share equivalent classifications under AS 5604 and AS 1720.
- Recommended spec wording: "Spotted Gum (Corymbia maculata, C. citriodora or C. henryi) heartwood — AS 5604 Class 1 above-ground durability, Strength Group SD2 seasoned, Joint Group JD1 seasoned, F-grade F34 seasoned typical."
- Naturally resistant to termite attack — an additional durability benefit for exterior structural and decking work.
- Bushfire performance (AS 3959, BAL ratings) is assessed independently and must be verified for the applicable BAL zone. Spotted Gum is listed in AS 3959 Appendix F — confirm current standard for specific BAL approval.
- For coastal or high-exposure UV applications, oil within 2 weeks of install then 12-monthly maintenance to preserve the natural colour and minimise surface checking.
References
Speccing Spotted Gum for a project?Spotted Gum for a project?
Send us your project specs — application, sizes, quantities, finish — and we'll quote with lead times. Spotted Gum is one of our most commonly stocked species, with regular runs of decking, cladding and structural sections from our Brisbane yard.