Merbau Decking: The Complete Guide to Cost, Lifespan, Installation and Care

Few materials change how a home feels like a timber deck. Walk onto a well-built merbau deck on a warm Melbourne evening and you’ll notice the colour first: a deep red-brown that makes a backyard feel like part of the house.

But merbau isn’t a “buy it and forget it” product. It can bleed tannins onto your pavers, it needs oiling, and it competes with composite and treated pine on price. Choosing well means knowing the trade-offs.

At Roots Timber & Hardware in Cranbourne East, we’ve supplied timber to Melbourne homeowners, builders and landscapers for over 20 years. This guide covers what merbau is, how long it lasts, what it really costs, and how to keep it looking good. By the end, you’ll know whether it’s the right deck for you.

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What Is Merbau Decking?

Merbau decking is a dense, naturally durable tropical hardwood decking made from the Intsia genus of trees (mainly Intsia bijuga). It is known for its deep red-brown colour, high hardness and good resistance to rot and termites when used above ground.

Merbau has been a popular decking choice in Australia for decades because it balances appearance, strength and price. You can read the botanical background on Wikipedia’s Intsia bijuga page.

Key Characteristics of Merbau Timber

• Colour: Light brown to deep red-brown that mellows to a silver-grey if left unoiled
• Density: Hard and heavy, which gives good wear resistance for high-traffic areas
• Durability: Rated as a Class 1 durability timber above ground under Australian Standards
• Grain: Straight to interlocked, with a coarse, even texture
• Natural oils and tannins: These help protect the timber but are also the cause of “bleeding”

Where Does Merbau Come From?

Merbau is a tropical hardwood grown in parts of South-East Asia and the Pacific, including Indonesia, Papua New Guinea and the Solomon Islands. Because it’s imported, the supplier’s sourcing practices matter (more on this below).

What Are the Pros and Cons of Merbau Decking?

Advantages of Merbau Decking

• Beautiful, rich colour that suits both modern and traditional homes
• Strong and hard-wearing, suitable for families, pets and entertaining
• Naturally termite and rot resistant when installed correctly above ground
• Stable and straight boards compared with many softwoods
• Renewable finish: you can re-oil or sand it to refresh the colour at any time

Drawbacks to Consider

• Tannin bleed in the first months, especially in rain
• Regular maintenance: oiling once or twice a year to hold the colour
• Hard to work with: boards should be pre-drilled before screwing, or they may split
• Can get hot underfoot in direct summer sun
• Higher upfront cost than treated pine

Being upfront about the drawbacks matters. A deck that suits your lifestyle is better than a deck that was easy to sell.

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How Long Does Merbau Decking Last?

With correct installation and regular maintenance, merbau decking commonly lasts 25 years or more above ground.

Lifespan depends on four things:

1. Ventilation: Boards need airflow underneath to stay dry
2. Fixings: Use stainless steel or quality, corrosion-resistant screws (see our decking screws)
3. Sun and weather exposure: Unprotected decks weather faster
4. Maintenance: Regular cleaning and oiling slow surface checking and fading

For ground-contact applications, merbau is not the right choice. Use a suitable in-ground product, such as treated pine sleepers or hardwood posts.

Why Does Merbau Bleed, and How Do You Stop It?

Merbau bleeds because it contains water-soluble tannins and natural extractives. When rain or moisture hits the boards, these dissolve and run onto surrounding surfaces, leaving orange-brown or reddish stains.

What Causes Tannin Bleed?

Fresh merbau holds the most extractives. Rain, sprinklers and pool splash carry them out of the wood. Light-coloured surfaces such as pavers, concrete and rendered walls show it most.

How to Reduce Tannin Bleed

Before installation

• Ask your supplier for properly seasoned, dry stock
• Seal all board ends and cut faces before fixing
• Consider how water will drain off the deck, and where it will go

After installation

• Hose the deck down regularly during the first few months to flush out tannins
• Apply a quality penetrating decking oil, once the timber is dry, to slow the bleed
• Protect nearby pavers and concrete with a sealer before the deck goes in

Local tip: If your deck sits next to light pavers or a pool, plan the bleed management into the project from day one. It is much easier to prevent than to remove.

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How Much Does Merbau Decking Cost?

Merbau decking cost depends on board size, grade, length and supplier. The timber is only part of your budget. You also need to allow for framing, fixings, oil, labour and delivery.

Because prices change, we don’t publish a fixed rate in this guide. Check our current Merbau decking range, including our 140 x 19 boards, or request a quote.

What Affects the Price?

• Board profile and size (e.g., 90 x 19 vs 140 x 19)
• Grade and finish (select grade vs standard grade)
• Board length and how much waste your layout creates
• Quantity, because larger orders may attract better pricing
• Delivery distance within Melbourne

How to Estimate Your Budget

1. Measure your deck area in square metres
2. Add 10% for wastage and cuts
3. Divide by the coverage of your chosen board to find the linear metres needed
4. Add framing, fixings, oil and delivery

If you’d like a second opinion, our team can check your measurements and cut list.

Merbau vs Composite vs Treated Pine: Which Is Better?

Merbau offers natural hardwood looks and a long lifespan with regular maintenance. Composite offers low maintenance and consistent colour. Treated pine is the most budget-friendly, but typically needs more care to stay looking good.

Feature	Merbau	Composite	Treated Pine
Appearance	Natural, rich red-brown	Uniform, engineered look	Natural, lighter tone
Upfront cost	Mid to high	Mid to high	Lowest
Maintenance	Regular oiling	Low (cleaning only)	Regular sealing
Tannin bleed	Yes	No	No
Lifespan (above ground)	Long	Long	Moderate
Best for	Natural-timber lovers	Low-maintenance living	Tight budgets

Not sure which suits you? Browse our composite decking and treated pine decking, or order a free sample to compare in your own backyard light.

What Size Merbau Decking Boards Do You Need?

The most common merbau decking sizes are 90 x 19 mm and 140 x 19 mm. Wider boards cover more area and reduce the number of joints, while narrower boards give a more traditional look.

• 140 x 19 mm: A popular modern choice that gives a wide, clean appearance with fewer gaps
• 90 x 19 mm: A classic look with more board lines

For joist spacing, board thickness and fixing requirements, always follow the relevant Australian Standards and your builder or designer’s specifications. See Standards Australia for the timber framing standards, including AS 1684.

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How Do You Install Merbau Decking Properly?

Install merbau by pre-drilling every screw hole, using corrosion-resistant fixings, leaving a small gap between boards for drainage and expansion, and making sure the frame is well ventilated.

Choosing the Right Fixings

Merbau is hard, and cheap screws can snap or corrode and stain the timber. Use quality decking screws suited to hardwood. Our decking screws range is a good starting point.

Framing and Spacing

• Build a level, well-supported frame using appropriate bearers and joists
• Use post stirrups and joist hangers as designed
• Leave a gap between boards (commonly 3 to 5 mm, depending on the timber’s moisture content and your installer’s advice)
• Keep boards off the ground, and ensure airflow underneath

Do You Need a Permit?

Decks can require a building permit depending on height, size and location. Check with the Victorian Building Authority and your local council before you build.

How Do You Maintain and Oil Merbau Decking?

Clean your merbau deck with a mild detergent and soft broom, let it dry fully, then apply a penetrating decking oil. Most owners re-oil once or twice a year, depending on sun exposure.

Step-by-Step Merbau Care

1. Sweep debris and leaves regularly so moisture doesn’t sit on the surface
2. Wash with a timber deck cleaner and soft-bristle brush
3. Rinse thoroughly and let the deck dry fully (usually 24 to 48 hours)
4. Lightly sand any rough or greyed patches if needed
5. Apply oil in thin, even coats with a brush or applicator, following the manufacturer’s instructions
6. Wipe off excess to avoid a sticky or patchy finish

Common Maintenance Mistakes

• Pressure-washing too aggressively, which can raise the grain
• Oiling over damp timber
• Skipping the first-year oil, when bleed and weathering are at their peak

Is Merbau Decking Sustainable and Legal to Buy in Australia?

Merbau can be a responsible choice if it’s sourced legally and, ideally, from verified or certified supply chains. Always ask your supplier where the timber comes from.

Merbau is a tropical timber, so sourcing matters. In Australia, importers must comply with the Illegal Logging Prohibition Act 2012, administered by the Department of Agriculture, Fisheries and Forestry. For certification, look at the Forest Stewardship Council.

A trustworthy supplier should be happy to answer questions about origin and compliance. If you’d like to know about our current stock, contact our team.

Is Merbau Decking Suitable for Bushfire-Prone Areas?

Some timbers, including certain hardwoods, are accepted for use in bushfire-prone construction under AS 3959, but requirements depend on your Bushfire Attack Level (BAL) rating and your design.

If your property is in a bushfire-prone area, confirm requirements with your building surveyor or designer before purchasing. Don’t assume any timber is automatically compliant. See Country Fire Authority (CFA) resources for guidance.

Frequently Asked Questions About Merbau Decking

How long does merbau decking last?

With proper installation and maintenance, merbau decking commonly lasts 25 years or more when used above ground.

Does merbau decking need to be oiled?

Oiling isn’t mandatory for the timber’s structure, but it’s strongly recommended. Without oil, merbau fades to a silver-grey and is more prone to surface checking.

Why is my merbau deck leaving orange stains?

That’s tannin bleed. It’s a natural reaction between rainwater and the timber’s extractives. It usually reduces over time, and regular rinsing and oiling help.

Is merbau better than composite decking?

Neither is “better” for everyone. Merbau suits people who want natural timber and don’t mind maintenance. Composite suits those wanting minimal upkeep.

Can I use merbau decking around a pool?

Yes, merbau is commonly used around pools, but plan for tannin bleed and protect light-coloured surfaces nearby.

Does merbau decking get hot in summer?

Like most timber, it can become warm in direct sun, though usually less than some darker synthetic products. Shade and light-coloured outdoor rugs help.

Conclusion: Is Merbau Decking Right for You?

Merbau decking gives you a hard-wearing, beautiful deck that can last decades, if you’re prepared for the early tannin bleed and regular oiling. If you prefer a lower-maintenance finish, composite may suit you better. And if budget is the priority, treated pine is worth a look.

Whichever you choose, a quality supplier makes all the difference, from board selection to the right screws and advice on layout.

Ready to Build Your Dream Deck?

Browse our Merbau decking range, get a free quote, or order a free sample to see the colour in your own backyard. You can also call us on (03) 5905 1984 or visit us at 1468 Thompsons Rd, Cranbourne East VIC 3977.

Roots Timber & Hardware: quality decking and timber supplies, delivered across Melbourne.