2. Is Merbau Good for Decking?
3. Choosing the Right Merbau Board
5. Merbau Decking Installation
6. How to Maintain Merbau Decking
7. Merbau Decking Troubleshooting
Merbau remains Australia's most popular hardwood decking timber because it combines exceptional durability, stability, natural beauty and value for money. In this guide we'll explain everything you need to know before buying Merbau decking.
What is Merbau Timber?
Merbau is a premium, durable hardwood timber native to Southeast Asia and the Pacific, widely used in Australia for outdoor decking and landscape design.
Is Merbau Good for Decking?
Yes, Merbau is exceptionally good for decking. It is highly sought after due to its Class 1 durability rating, natural resistance to pests, and superior dimensional stability compared to other hardwoods.
How Long Does Merbau Decking Last?
Merbau is rated Class 1 for durability above ground - when properly installed and maintained, it can provide more than 40 years of reliable performance outdoors, with an average expected life expectancy of 25-40 years.
Why is Merbau Considered More Stable Than Other Decking Timbers?
Merbau has superior stability to other timber species, which means less movement (shrinkage) and lower rates of splitting, cupping, twisting, and warping.
Is Merbau Resistant to Bushfires and Pests?
Merbau is highly resilient against the elements and problematic pests:
- Bushfire Rated: BAL 29 rated, making it suitable for use in areas prone to bushfires.
- Pest Resistant: Naturally resistant to termites, dry wood borers, and fungi.
Note: Always follow guidance from your local building authority to ensure compliance in bushfire-prone areas.
Is SpecRite Merbau Sustainably Sourced?
Yes. All SpecRite Merbau is sustainably sourced from FSC®-certified forests, ensuring responsible forestry practices. Not all Merbau on the market is certified, so look for the FSC label before purchasing.
Learn more in our article: Why Choose FSC-Certified Timber?
Does Merbau Decking Look Good?
Yes, Merbau has a beautiful, rich colour, which varies from a light yellow-brown to a deep reddish brown and has an even, straight grain, with occasional golden flecks running through it. It offers a premium, natural look that complements a wide variety of architectural and landscaping styles, from traditional homes through to modern outdoor entertaining spaces.
Research also shows that integrating natural materials (like timber) into our living spaces, has been shown to reduce stress and create more restorative environments, according to a recent study on biophilic design benefits.
What Else Can Merbau Be Used For?
Merbau can be used for decking, screening, fencing, pergolas, feature walls, seating and other outdoor structures.
Unlike composite alternatives, merbau is available in a wide range of pre-sized profiles and lengths, meaning it can be used for a whole range of outdoor landscaping projects and features.
This flexibility opens up endless design possibilities and allows you to create a cohesive outdoor aesthetic. Explore your options by browsing the full SpecRite Merbau product range.
Merbau vs Composite Decking – Which Offers Better Value?
For most homeowners, Merbau offers better long-term value than composite decking, as well as outperforming treated pine decking and other hardwood alternatives.
Compared with plastic composite decking options, not only is Merbau nearly half the price, but for homeowners valuing natural beauty and durability, Merbau remains a superior choice when sourced responsibly and maintained properly.
If you're torn between natural timber and synthetic options, check out our head-to-head comparison: Merbau vs. Composite Decking.
Choosing the Right Merbau Board
Should I Choose Pre-oiled Merbau Decking?
Yes. Choosing pre-oiled Merbau decking is highly recommended because it provides immediate protection against moisture and UV damage during transit and installation. All SpecRite Merbau decking comes pre-oiled to give your timber an upfront layer of defence before you apply your final topcoat, as well as added protection to the underside of the decking boards.
Should I use Narrow or Wide Merbau Decking Boards?
The choice between narrow (90mm) and wide (140mm) boards depends on your deck's clearance height and design preferences:
- Choose 90mm boards for low-level decks, as the narrower profile offers superior structural stability and allows for more frequent ventilation gaps to prevent moisture buildup underneath.
- Choose 140mm boards if you are looking to achieve a modern, premium aesthetic on a standard, elevated deck.
- Choose a mix of both in a unique combination to elevate the look of your outdoor space.
What is the difference between solid random lengths and finger-jointed decking?
The main difference lies in how the boards are manufactured, which impacts their visual appearance, installation speed, and budget:
- Solid Random Lengths: A traditional mix of varying board lengths from 1.8m to 5.7m designed to create a classic, staggered butt-join deck layout.
- Side Finger Jointed Set Lengths: Uniform 5.7m boards made by precision joining 3-4 colour-matched pieces of timber. They feature a discreet side join and come with a 25-year warranty (limited to joint failure).
- Face Finger Jointed Bundles: An easily transportable, budget-friendly option (~1 sqm bundles) featuring visible, interlocking finger joins on the face of the boards.
Planning Your Merbau Deck
Are Decks Subject to Building or Planning Permits?
Decks can be subject to both building and planning requirements. Before you start planning your deck, it pays to find out if there are any legal building requirements for your specific project.
- Planning Permits: Requirements can depend on various things, including the size of your property, the elevation of your deck and any local council overlays (e.g. Heritage, Bushfire Management or Flood/Inundation Overlays).
- Building Permits: these are more focused around structural safety, and ensuring the design complies with relevant codes and standards. You will almost certainly need a building permit if your deck is attached to an existing structure, built above your state’s height threshold, is close to a property boundary line, or forms part of a swimming pool enclosure.
- Building Permit Exemptions: In some states, a small, unroofed, freestanding deck that is close to natural ground level (usually under 600mm to 1000mm depending on your state) may be exempt from a building permit. Exemption thresholds vary significantly between states and often between councils within a state.
The National Construction Code is a great place to start, but regulations can also vary between states and regions. Always check with your local council or a private building certifier before buying materials.
How Do I Know How Much Decking I Need?
For decking boards, the number of lineal metres you need can be found by dividing the area of the deck by the width of the decking boards. Don’t forget to incorporate ventilation gaps and add approximately 10% extra to your order for wastage and offcuts.
If you want to skip the manual calculations, use our free online decking calculator.
What Materials Should I Use for My Subframe?
The most common framing material for a decking subframe is treated pine, with alternatives including hardwood and galvanised steel. Structural framing typically requires F7 or MGP10 grade timber and timber in contact with the ground must be rated H4 or higher. H3 timber can be used for above ground bearers and joists.
To find the correct distance between decking posts (post spacing) and bearers (bearer span), you must use Australian Standard AS 1684 span tables. The exact distances depend on your timber species, stress grade, and whether the deck is single-span or continuous-span.
Should I Use Nails or Screws for Decking?
Stainless steel screws are highly recommended – two screws per joist – minimum 12g 50mm.
Dome head nails that protrude from the timber can make the deck difficult to sand down and nailing should generally be avoided to minimise the risk of splitting the timber.
Merbau Decking Installation
While building a deck is a rewarding project, getting the installation details right will help ensure your deck looks great and lasts a lifetime.
Step 1 – Prepare the Frame
Fix your stumps, bearers, and joists.
Step 2 – Set Board Spacing
Accurate gapping is crucial to allow for natural timber expansion and ventilation. Aim for a minimum 5% gap between boards.
Step 3 – Fix the Boards
Pre-drill your holes using a countersink bit to avoid splitting the hardwood, then secure each board using two 50mm stainless steel screws per joist.
Step 4 – Finish and Protect the Deck
Apply a dedicated topcoat to seal the wood and lock in protection against heavy UV and moisture exposure.
For a comprehensive walkthrough of the entire building process, explore our step-by-step guide on How to Build a Deck and read our complete Merbau Decking Installation Guide.
How to Maintain Merbau Decking
Maintaining Merbau decking is simple. Clean it regularly and recoat it when the existing finish begins to wear and your Merbau deck will thrive.
We recommend applying a topcoat as soon as possible after installation to provide maximum protection to the timber. Our pre-oiled products can be top-coated with either an oil-based or water-based coating.
Depending on your local climate and your chosen topcoat, your deck could need refreshing every six months, or every few years. A high-end water-based finish will give you the longest lasting protection.
Follow our instructions on how to properly clean a timber deck, followed by how to topcoat your Merbau deck.
Merbau Decking Troubleshooting: Problems and Solutions
Why is My Deck Leaching Brown Liquid?
This is known as tannin bleed. Tannin is a natural substance in timber that leaches during its first few exposures to moisture, potentially staining nearby concrete or paving. You can naturally wash the tannins out with repeated hose-downs or apply a dedicated tannin remover upfront before final top-coating.
Why are My Decking Boards Moving?
It’s likely that the moisture below the deck is too high.
This can be caused by insufficient gapping, or limited airflow underneath the deck. Before building your deck, we recommend reading our Merbau Decking Installation Guide and factoring adequate ventilation, and additional drainage where needed.
Why is My Deck Turning Grey?
Because UV exposure gradually breaks down the colour at the timber surface if it isn't protected by a UV coating.
All outdoor timbers eventually grey off without maintenance. While some homeowners prefer the rustic, silvered off look, if you want to keep your deck’s rich colour it’s important to maintain a re-oiling schedule in line with your chosen top-coating product, and your local climate.
What are the Dark Patches on my Deck?
This is likely to be caused by iron stain, where trace metals – e.g. from muddy work boots, wire brushes, or cutting metal over your deck – react with the tannins in the timber, causing a chemical reaction. It can also be caused by poor quality fixings – stainless steel decking screws are recommended to avoid contamination from fixings.
Iron stain can occur in all timbers, and the best way to deal with it is to remove the source of the metal and clean the deck with an oxalic-based timber cleaner to remove the stains.
Ready to start your project? Browse our range of FSC® certified Merbau decking available at Bunnings.
The FSC® logo identifies products from forests that are certified against a set of strict environmental, social and economic standards in accordance with the rules of the Forest Stewardship Council®. You can check the current certification status of our SpecRite Merbau supplier at any time by visiting the FSC Search at search.fsc.org/en/ and entering Licence Code: FSC®-C128536.