Spotted Gum, Blackbutt and Ironbark are the three hardwoods you will see quoted again and again for external timber stairs in Brisbane. All three are Australian-grown, all three suit our subtropical climate, and all three look stunning under an oil finish. The differences come down to durability class, hardness, cost and how each one weathers.
Quick Verdict
- Best all-rounder for Brisbane: Spotted Gum. Class 1 durability above ground, mid-price, easy to source.
- Best for coastal Sunshine Coast jobs: Ironbark. Highest durability, holds up under salt spray.
- Best on a budget: Blackbutt. Class 2 durability, lighter colour, slightly cheaper than Spotted Gum.
Side-by-Side Comparison
| Property | Spotted Gum | Blackbutt | Ironbark |
|---|---|---|---|
| AS 5604 durability (above ground) | Class 1 | Class 2 | Class 1 |
| Janka hardness | 11.0 kN | 9.1 kN | 14.0 kN |
| Density (kg/m³) | ~950 | ~900 | ~1100 |
| Realistic lifespan (SEQ external) | 25-35 years | 20-25 years | 40+ years |
| Heartwood colour | Chocolate to honey | Pale gold to brown | Deep red-brown |
| Weathers to | Soft silver-grey | Light silver | Dark silver-grey |
| Cost tier (2026) | $$ mid | $$ mid | $$$ premium |
| Workability | Good | Very good | Demanding |
Spotted Gum in Detail
Spotted Gum (Corymbia maculata) is the default external stair timber in South-East Queensland for good reason. It grows abundantly across the NSW north coast and South-East Queensland, so supply is reliable. Density is around 950 kg/m³, hardness 11 kN, and AS 5604 lists it as Class 1 durability above ground.
Heartwood ranges from light brown through to a rich chocolate, often with visible gum veins that add character. Under a UV-blocking oil it holds the honey-brown tones for 18 to 24 months between coats; left bare it weathers to a soft silver-grey within 12 months.
Blackbutt in Detail
Blackbutt (Eucalyptus pilularis) is the lightest-coloured of the three — a pale gold that suits beach-house aesthetics on the Sunshine Coast. Density around 900 kg/m³ and Janka 9.1 kN make it the easiest of the three to mill and finish, which keeps fabrication labour down.
The trade-off is AS 5604 Class 2 durability above ground — about 20 to 25 years in a Brisbane external application. It still has BAL-29 bushfire rating and resists Lyctus borer, so it remains a strong mid-tier pick for sheltered or partly-covered stairs.
Ironbark in Detail
Grey Ironbark (Eucalyptus paniculata) and Red Ironbark (E. sideroxylon) are the heavyweights — density 1100 kg/m³, Janka 14 kN, AS 5604 Class 1 durability above and in ground. The realistic lifespan in a Brisbane external application is 40 years plus with basic maintenance.
Ironbark is the species to specify for stairs facing direct salt spray at Mooloolaba, Caloundra or Bribie Island, or for high-traffic commercial settings. Expect 30 to 50% higher cost and a longer lead time, plus a builder who is comfortable working it.
Which Should You Pick?
- Inner Brisbane, standard residential: Spotted Gum — best balance of price, durability and look.
- Sunshine Coast within 5 km of the ocean: Ironbark — the salt-air premium is worth it.
- Light contemporary aesthetic, sheltered stair: Blackbutt — cheaper, paler, easier to source.
- Heritage Queenslander rebuild: Spotted Gum or Ironbark — both turn cleanly for traditional balusters. See our Queenslander external stairs guide.
For broader species background see our best timber for outdoor stairs in Queensland guide, or our full external timber stairs across SEQ service page.
Craftsman Stairs has milled all three species in our North Brisbane workshop since 1989 — call 0439 730 583 to talk through the right pick for your job. QBCC 69007 · ABN 86 475 603 796.
Frequently Asked Questions
Which is the most durable for Brisbane external stairs — Spotted Gum, Blackbutt or Ironbark?
Ironbark is the most durable above ground (AS 5604 Class 1, 40+ year lifespan) followed by Spotted Gum (Class 1, 25-35 years) and Blackbutt (Class 2, 20-25 years). All three suit external stairs in the Brisbane and Sunshine Coast climate when detailed and maintained correctly.
Is Spotted Gum cheaper than Blackbutt for external stairs?
Spotted Gum and Blackbutt sit at a similar price tier in South-East Queensland — typically $4,200 to $5,400 per cubic metre for structural grade in 2026. Ironbark runs roughly 30 to 50% higher because supply is tighter and the timber is harder to mill.
Will Blackbutt grey off the same as Spotted Gum if left unfinished?
Both weather to a silver-grey if left unfinished, but Blackbutt greys lighter and slightly faster because its lignin content is lower. Spotted Gum holds its honey-brown tones noticeably longer under a UV-blocking decking oil.
Is Ironbark too hard to work for stair treads?
Not for an experienced workshop. Ironbark has a Janka hardness of around 14 kN — about 50% harder than Blackbutt — so cutting and machining is slower and requires tungsten-tipped tooling. The reward is exceptional dent and wear resistance once installed.
Craftsman Stairs
QBCC licensed staircase builders with over 35 years of experience servicing North Brisbane, Moreton Bay and the Sunshine Coast. We design, manufacture and install custom staircases for residential and commercial projects.
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