Cumaru Decking for Sydney: Durability, Cost & Comparison to Merbau 2026
If you’re hunting for a premium hardwood deck in Sydney that won’t cost you an arm and a leg or demand constant maintenance, Cumaru deserves serious consideration. It’s one of the toughest tropical hardwoods available, rivals Merbau in durability, and delivers a rich golden-brown finish that weathers beautifully over time.
Here’s what you need to know before committing to Cumaru for your Sydney deck in 2026.
What is Cumaru?
Cumaru (also called Tonka bean wood or Brazilian hardwood) is a dense tropical hardwood harvested from South America, primarily Brazil and Venezuela. It’s known in the industry for extreme hardness and natural oil content that resists rot, termites, and weathering—properties that make it ideal for exposed outdoor decking.
On the Janka hardness scale, Cumaru rates around 2350—slightly harder than Merbau (2250) and significantly tougher than standard Australian hardwoods like spotted gum (1300). This density means it resists scratching, denting, and splintering under foot traffic and furniture weight.
Cumaru vs Merbau: The Direct Comparison
| Property | Cumaru | Merbau |
|---|---|---|
| Janka Hardness | 2350 | 2250 |
| Colour | Golden-brown to reddish-brown | Rich reddish-brown |
| Density | Very high (~1.0 g/cm³) | Very high (~0.9 g/cm³) |
| Rot Resistance | Excellent (Class 1) | Excellent (Class 1) |
| Price (2026, Sydney) | $85–$120/m² | $75–$100/m² |
| Maintenance | Annual oiling recommended | Annual oiling recommended |
| Lifespan | 25–40 years (above ground) | 25–35 years (above ground) |
In short: Cumaru is slightly harder and slightly more expensive than Merbau, but performs virtually identically in Sydney’s coastal and suburban climates. The choice often comes down to aesthetics (golden vs. reddish tone) and budget.
Cumaru Costs in Sydney 2026
Material pricing varies by supplier and board quality, but expect:
- Decking boards (25mm x 90–140mm): $85–$120 per square metre installed (labour extra)
- Supply-only: $45–$70/m² for raw timber
- Fasteners & accessories: $8–$12/m² (stainless steel screws recommended)
For a typical 4m × 4m deck (16m²), you’re looking at $1,360–$1,920 in materials alone, or $3,200–$4,800 installed (including labour, joists, and finishing).
Why Choose Cumaru?
Extreme Durability
Cumaru’s natural oils and tight grain structure make it naturally resistant to rot, termites, and fungal decay. It doesn’t require chemical treatment (unlike softwoods), so it’s a safer choice for families and pets.
Minimal Splinter Risk
The density and tight grain mean splintering is rare, even after several years of exposure. Barefoot kids and pets are safer on Cumaru than on softer Australian hardwoods.
Premium Appearance
The warm golden-brown colour adds luxury to your outdoor space. It weathers to a silver-grey patina over 7–10 years, or you can maintain the warm tone with annual oiling.
Sustainable (Responsibly Sourced)
Cumaru is harvested from responsibly managed FSC-certified forests in Brazil. It’s more sustainable than imported tropical hardwoods that come from uncontrolled logging.
Drawbacks to Consider
Cost Premium
Cumaru is 10–20% more expensive than Merbau or Australian hardwoods, which can add up on larger decks.
Annual Maintenance
To preserve the warm golden tone (and not let it weather to grey), you’ll need to oil the deck annually. This is a half-day job for a 4m × 4m deck and costs $150–$300 in product.
Sourcing Delays
Cumaru isn’t stocked by every timber supplier in Sydney. Lead times can be 4–8 weeks if your builder needs to special-order.
Weight
Cumaru is dense (~1000 kg/m³), so shipping and handling costs are higher than lighter hardwoods. Installation labour may also be slightly more due to the weight.
Cumaru vs Composite Decking
If you’re torn between hardwood and composite (like Evalast or Modwood), here’s the trade-off:
- Cumaru: Natural look, premium feel, needs annual oiling, lasts 25–40 years, warmer underfoot.
- Composite: Low maintenance, consistent colour, lasts 25–30 years, slightly cooler underfoot, higher upfront cost ($150–$200/m² installed).
If you want a natural hardwood deck with minimal fuss and don’t mind annual oiling, Cumaru wins. If zero maintenance is your priority, composite is the better choice.
Cumaru Installation Tips for Sydney
Joist Spacing
Use 450mm joist spacing (on-centre) to prevent deflection over time. The weight of Cumaru requires robust support.
Fastening
Use marine-grade stainless steel screws (not nails). Pre-drill all holes to prevent splitting in this dense hardwood.
Underdecking & Drainage
Cumaru is rot-resistant but still benefits from good underdecking airflow. Install joist tape and ensure deck slopes 1:100 for water run-off.
First Coat
Oil the deck within 4–6 weeks of installation, then annually thereafter. Use an external hardwood oil or deck stain to maintain colour.
Is Cumaru Right for Your Sydney Deck?
Choose Cumaru if you want:
- A premium, long-lasting hardwood deck with minimal rot/termite risk
- Natural wood aesthetics with warm golden tones
- A deck that’s safe for barefoot use and pets
- Something tougher than standard Australian hardwoods
Skip Cumaru if you prefer:
- Zero-maintenance decking (composite is better)
- Budget decking under $2,500 for 16m² (softwood or light composite)
- Instantly silvered, weathered look (Cumaru needs oiling to stay golden)
Ready to Explore Cumaru for Your Deck?
At 5 Star Decking, we’ve built dozens of Cumaru decks across Sydney—from coastal Cronulla to suburban Eastwood. We source responsibly harvested timber, handle the weight properly, and guide you through maintenance so your deck stays beautiful for decades.
Get a free quote and discuss whether Cumaru is right for your space. Contact us today or call 0433 334 415. NSW License 395250C.
5 Star Decking builds premium composite and hardwood decks across Sydney, from Bondi to Penrith. All work is backed by our 10-year guarantee and certified by NSW License 395250C.
