Durability
Class 1, very durable
Expected life of 40+ years outside above ground and 25+ years in ground, or 50+ years fully protected. Exceptional resistance to decay.
Merbau Supplier in Adelaide – Durable Hardwood for Outdoor Projects
Durable Hardwoods is a Merbau supplier in Adelaide. We specify and source Merbau to order for decking, posts, cladding, jetty decking and boardwalks, and deliver it across SA, with delivery also available to VIC, NSW and QLD.
Merbau is one of the world's most trusted external hardwoods and our most popular species. It is prized for its durability, natural beauty and range of outdoor uses.
Why Merbau
Merbau doesn't just look good, it performs. From its Class 1 durability rating to its natural resistance to termites and moisture, it is built for the Australian outdoors.
Hazard level
H4–H5
Rated for in-ground use with severe wetting (H4) and in-ground or fresh-water use with extreme wetting (H5).
Termite and ant resistance
Excellent
Naturally resistant to termite and ant attack thanks to its high oil content, which matters for Australian outdoor structures.
Bushfire rating
BAL-29
Well regarded for bushfire-prone areas, where timber must withstand ember attack and moderate to high radiant heat.
Strength and hardness
F11–F14 stress grade
Hard, dense, stiff and stable, with a Janka hardness of 8.6 kN and a density of about 830 kg/m³. Resists denting, scratching and heavy foot traffic.
Moisture resistance
Natural oils
Natural resin oils repel moisture, reducing swelling and shrinkage in wet or coastal settings.
What is Merbau?
Merbau (Intsia bijuga), also traded as Pacific Teak, is a tropical hardwood from Southeast Asia and the Pacific. It has been a mainstay of outdoor construction in Australia for decades.
Its deep reddish-brown heartwood, interlocked grain and natural oils make it highly resistant to moisture, insects and decay. It handles the harsh Australian climate well, including coastal salt air, strong UV and extreme heat.
We source Merbau to order through our Australian and international mill network. Sourcing documentation is available on request.
Kwila (Intsia palembanica) is a closely related species with its own ratings on our poster.
Applications
Hardness, natural oils and warm colour make Merbau a first choice for architects, builders, councils and landscapers.
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Decking
The benchmark for external decking in Australia. Its hardness stands up to heavy foot traffic and its oils protect against moisture, so the deck stays good-looking for decades.
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Cladding and screening
Rich, warm tones make Merbau an architect favourite for external cladding and privacy screens. It weathers with character and handles UV exposure well.
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Fencing and posts
Strength and long life in equal measure. Class 1 durability suits exposed posts and palings in every Australian climate zone. See also our fence posts.
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Landscaping and retaining
From garden edging to retaining walls and planter boxes, Merbau performs under constant soil contact and moisture, and outlasts treated pine alternatives.
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Jetty decking, bridges and walkways
Widely specified for public boardwalks, bridges, and jetty and pier decking, including council and government infrastructure, for its structural strength and performance in coastal settings. Merbau is rated H4–H5, so it suits decking and structures above the water line. Piles and members permanently in sea water need H6 timber. Ask us which species suit.
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Pergolas and structures
High density and structural grade make Merbau well suited to pergolas, carports and feature structures that need to carry load and look good.
Species characteristics
A closer look at the properties that make Merbau one of Australia's most trusted external hardwoods.
| Property | Detail |
|---|---|
| Botanical name | Intsia bijuga |
| Colour | Rich reddish-brown to dark brown, often with golden streaks. Deepens and mellows with age and UV exposure. |
| Grain | Interlocked to wavy. Coarse texture with a lustrous surface. Takes a smooth finish well. |
| Working properties | Machines well. Carbide-tipped tools recommended. Glues, nails and screws satisfactorily. Pre-drilling advised. |
| Durability class | Class 1 (very durable), the highest classification under AS 5604. 40+ years outside above ground, 25+ years in ground, 50+ years fully protected. |
| Stress grade (F rating) | F11–F14 |
| Hazard level (H rating) | H4–H5 |
| Janka hardness | 8.6 kN |
| Density | About 830 kg/m³ at 12% moisture content |
| Bushfire attack level | BAL-29 |
| Termite and ant resistance | Excellent |
| Recommended treatment | Oil finishes; minimal treatment |
| Tannin bleed | A natural characteristic when first exposed to rain. Reduces over time. Pre-oiling and good drainage detailing minimise staining. |
| Maintenance | An annual coat of quality penetrating oil is recommended. Left untreated, Merbau weathers to silver-grey with no loss of structural integrity. |
| Sourcing | Sourced to order from responsibly managed suppliers in our mill network. Sourcing documentation available on request. |
Sizes, supplied to order
Every Merbau order is sourced for your project from our mill network. Tell us the sizes and quantities you need and we'll quote the job.
- 90 × 19Decking
- 140 × 19Decking
- 140 × 45Decking
- StructuralPosts, rails and palings
- CustomMill sizes on request
Common questions
Do Merbau posts need treatment for in-ground use?
Merbau is a Class 1 (very durable) species on our Australian Hardwoods poster, rated H4–H5, with an expected life of 25+ years in ground and 40+ years outside above ground. The poster's recommended treatment is oil finishes and minimal treatment, rather than a chemical preservative. Good drainage, ventilation and ground clearance still help any post last longer.
How do I maintain Merbau decking?
Clean and re-oil Merbau every year for the first 2–3 years, then every 1–2 years once it has stabilised. Use an oil made for dense, oily hardwoods. If you leave it untreated it weathers to silver-grey, with no loss of structural integrity.
What is tannin bleed, and how do I deal with it?
Tannin bleed is a natural characteristic of Merbau when it is first exposed to rain, and it reduces over time. Pre-oiling and good drainage detailing minimise staining, and a tannin inhibitor can be applied before installation. To remove stains, use an oxalic acid-based timber cleaner and rinse thoroughly.
Is Merbau suitable for bushfire-prone areas?
Merbau is rated BAL-29 on our poster. Your site's own BAL rating is set by a qualified bushfire consultant or certifier, usually during development approval, and local councils keep maps of bushfire-prone areas.
Can Merbau be used for jetties?
Yes, for jetty and pier decking and structures above the water. Merbau is rated H4–H5. Piles that sit in sea water need H6, the marine hazard level, so ask us about treated timber for those parts.
Get a free assessment & quote
Tell us what you are building, where, and the conditions it has to handle. Matt will come back with the right species, grade and sizes, priced for your job.