Short answer: you are choosing between two of the most capable decking timbers in the Australian hardwood range. Both Ironbark and Spotted Gum carry supplier-published Class 1 above-ground durability with a 40+ year rating, both are very hard Australian hardwoods, and Sydney Timber Supply sells both in the same board sizes at per-linear-metre pricing. The decision usually comes down to look: Spotted Gum is known for its striking grain, while Ironbark is prized as a very hard, dense workhorse. This guide compares them point by point so you can commit with confidence.
Quick comparison
| Factor | Ironbark | Spotted Gum |
|---|---|---|
| Origin | Australian hardwood | Australian hardwood |
| Durability (above ground) | Class 1, 40+ years (supplier-published) | Class 1, 40+ years (supplier-published) |
| Hardness | Very hard, dense | Very hard |
| Character | Dense, heavyweight board | Striking grain |
| STS decking sizes | 86 x 19 mm, 135 x 19 mm, 135 x 35 mm (140 x 35 mm option) | 86 x 19 mm, 135 x 19 mm, 135 x 35 mm (140 x 35 mm option) |
| How it is sold | Per LM, random lengths (preferred lengths by quote) | Per LM, random lengths (preferred lengths by quote) |
Colour and grain
This is where the two species genuinely part ways. Spotted Gum's supplier specification sheets single out its striking grain, and it is the board people tend to pick when they want the deck itself to be the feature. Ironbark's reputation is built on density and toughness rather than figure.
Because hardwood is a natural product, colour and grain vary from board to board and pack to pack. Rather than choosing off a written description, look at the photography on our Ironbark and Spotted Gum collection pages and the species guide, and if the final look matters to your project, talk to us about what is currently in the yard before you order.
Hardness and density
Both species are very hard Australian hardwoods, which is a large part of why they are so popular for decking. Ironbark in particular is described in supplier sheets as very hard and dense. In practical terms, hard dense boards stand up well to foot traffic, furniture and everyday knocks, and both species sit at the serious end of the hardwood spectrum. For a domestic deck, neither will be the weak link. Expect to pre-drill and to work a little harder on installation than you would with softwood; that is the trade-off for a deck surface this tough. It is the same hardness that outdoor furniture makers value; our team's background building Auscraft outdoor furniture in these species is where much of this advice comes from.
Durability: no separation between them
According to supplier specification sheets, both Ironbark and Spotted Gum are rated Class 1 for above-ground durability with a 40+ year rating. Class 1 is the highest natural above-ground durability class for timber, and STS only shows the Class 1 badge on hardwoods whose supplier sheets state it. In other words, durability is not the deciding factor here: on paper, the two species are equals. If durability class is what you are shopping on, the whole STS Australian hardwood range is worth a look.
Sizes and availability at STS
STS stocks Ironbark and Spotted Gum decking in the same profiles:
- 86 x 19 mm: the classic narrow decking board.
- 135 x 19 mm: a wide board that covers ground faster and reduces total linear metres.
- 135 x 35 mm: a thick profile, with a 140 x 35 mm option also available.
Both are sold per linear metre in random lengths, with preferred lengths available by quote. Because sizes and selling format are identical, you can compare the two species directly on the per-LM prices shown on the collection pages, and use the timber calculator to turn your deck area into an order quantity for either species.
So how do you choose?
- Choose Spotted Gum if the look of the deck is the priority and you want that striking grain on show.
- Choose Ironbark if you are drawn to a very hard, dense board and want the deck to feel like it was built to be used.
- Choose either with confidence on durability: both carry supplier-published Class 1 above-ground ratings at 40+ years.
- Compare on price and stock once the look question is settled, since sizes and pricing format are identical.
If you are still torn, it is worth seeing boards in person. Colour and grain photos help, but hardwood always reads differently in the flesh.
FAQ
Is Ironbark harder than Spotted Gum?
Both are very hard Australian hardwoods, and Ironbark is noted in supplier sheets for being dense as well. For decking use, both sit comfortably at the hard end of the range.
Do they last the same length of time?
Supplier specification sheets rate both species Class 1 above ground with a 40+ year rating. That is a supplier-published durability rating, not a guarantee, and real service life depends on design, installation and maintenance.
Can I get matching sizes if I mix species?
Yes. STS sells both species in 86 x 19 mm, 135 x 19 mm and 135 x 35 mm, so profiles line up if you are running different species across separate areas.
Talk to us
Undecided between the two? Send your project details through the request a quote page and we will help you weigh it up, or come and see the boards at our West Gosford yard. Bulk and pack quantities are quote-first, and delivery covers Sydney Metro, the Central Coast, Newcastle and the Hunter, and Wollongong and the Illawarra.
Sydney Timber Supply team
Technical details drawn from supplier specification sheets; reviewed 19 July 2026.