Mounts Bay Constructions
7 min read

Merbau Vs Composite Vs Timber Decking: What’s Actually Worth It For A Perth Home?

Your deck takes more punishment than any other surface on your property. Perth’s UV index regularly hits extreme levels. Salt air drifts inland further than most people realize. And that beautiful Merbau everyone’s been installing? It’s been leaving rust-coloured stains on limestone walls and pool surrounds across the western suburbs for years.

Choosing decking isn’t about picking what looks best in the showroom. It’s about understanding how materials behave in our specific climate—and how much time you’re willing to spend maintaining them over the next decade.

THE TANNIN PROBLEM NOBODY TALKS ABOUT UNTIL IT’S TOO LATE

Walk through any established Perth neighbourhood and you’ll spot the telltale signs: reddish-brown streaks down rendered walls, discoloured pavers, stained pool copings. Merbau’s tannin bleed is particularly aggressive, releasing water-soluble extractives for months—sometimes years—after installation.

This isn’t a defect. It’s the natural behaviour of timber extractives when exposed to moisture. But in Perth, where we get all our rain in winter followed by nine months of intense sun, that seasonal cycle creates perfect conditions for ongoing tannin release.

Tannin Bleed Risk Comparison

MaterialBleed RiskDurationStaining SeverityManagement Required
MerbauHigh6-24 monthsSevere – rust-red staining on all adjacent surfacesIntensive – multiple washes, oxalic acid treatment
BlackbuttLow-Medium2-4 weeksMild – light brown marksMinimal – initial weathering only
Spotted GumLow1-2 weeksMinimal – slight discolourationNone after initial wash
CompositeNoneNot applicableNo stainingNo management needed
Treated PineVery Low1 weekNegligibleSingle wash if any


The science behind timber leaching shows that tropical hardwoods like Merbau contain significantly higher levels of water-soluble extractives than Australian natives. These extractives are what give Merbau its natural durability—but they’re also what will stain your limestone for the next two summers.

THE REAL COST OF OWNERSHIP IN PERTH’S CLIMATE

Most quotes focus on supply and installation. But in our high-UV environment, maintenance costs can exceed the original installation price within a decade. Here’s what the numbers actually look like when you factor in Perth’s specific conditions:

True Cost Comparison (Perth Market 2024)

MaterialSupply Cost/m²Installed Cost/m²Annual Maintenance10-Year Maintenance CostTotal 10-Year Ownership
Merbau$60-80$200-250$15-20/m²$150-200/m²$350-450/m²
Premium Hardwood$100-150$300-400$15-20/m²$150-200/m²$450-600/m²
Treated Pine$40-60$200-250$20-25/m²$200-250/m²$400-500/m²
Composite (Premium)$80-150 supply only$250-450$2-5/m²$20-50/m²$270-500/m²

Note: Maintenance costs include materials and labour for oiling, sanding, and repairs. Perth’s extreme UV accelerates oil breakdown, requiring more frequent recoating than eastern states.

UNDERSTANDING MATERIAL BEHAVIOUR IN WA CONDITIONS

Perth presents unique challenges that don’t exist in Sydney or Melbourne. We’re dealing with nine months of intense UV exposure, winter rain that arrives all at once, and coastal salt that affects properties 20 kilometres from the beach.

Composite decking has evolved significantly from the plastic-looking boards of a decade ago. Modern composites use wood fibres and polymer caps that handle our UV levels without the constant maintenance cycle timber demands.

Maintenance Reality Check

MaterialFirst YearYears 2-5Years 6-10Owner Time Commitment
MerbauOil 3x, wash tannins monthlyOil 2x annually, sand every 2 yearsOil 2x annually, replace boards as needed40+ hours annually
Blackbutt/Spotted GumOil 2xOil annuallyOil annually, sand every 3 years20 hours annually
CompositeWash onceWash annuallyWash annually2 hours annually
Treated PineOil 3x, possible twist/warpOil 2x annually, replace warped boardsMajor restoration or replacement likely30+ hours annually

The comparison between timber and composite isn’t just about aesthetics anymore. It’s about understanding your tolerance for maintenance versus your desire for natural materials.

LONGEVITY & WARRANTY: WHAT’S ACTUALLY GUARANTEED

Warranty coverage reveals what manufacturers really believe about their products’ performance in Australian conditions:

Warranty and Lifespan Comparison

MaterialStructural WarrantyFade/Stain WarrantyRealistic Lifespan (Perth)Replacement Triggers
MerbauNone (natural product)Not applicable15-20 years with maintenanceRot, splitting, severe weathering
Australian HardwoodNone (natural product)Not applicable20-25 years with maintenanceStructural degradation
Treated PineUp to 25 years (in-ground)Not applicable8-12 yearsWarping, splintering, rot
Premium Composite25-30 years25 years25-30 yearsUnlikely within warranty period

These aren’t theoretical numbers. They’re based on actual performance in WA’s climate, where UV degradation happens 30% faster than the Australian average.

MAKING THE RIGHT CHOICE FOR YOUR PROPERTY

Choosing between timber and composite comes down to three factors that matter more than initial aesthetics:

Choose Merbau if:

  • You love the natural timber look and feel
  • You’re committed to regular maintenance
  • Tannin staining won’t affect adjacent surfaces
  • You have the budget for ongoing upkeep

Choose Composite if:

  • Low maintenance is a priority
  • You have a pool or light-coloured surrounds
  • Long-term cost matters more than upfront price
  • You want guaranteed performance for 20+ years

Choose Alternative Timbers if:

  • You want natural timber without tannin issues
  • You prefer Australian species
  • You’re willing to maintain but want to avoid Merbau’s staining
  • Your property suits the silver-grey weathered look

THE SUSTAINABILITY QUESTION

Modern composite decking contains up to 95% recycled content—reclaimed wood fibres and recycled plastic that would otherwise go to landfill. Quality timber comes from managed forests, but the oils and treatments required for maintenance carry their own environmental load.

The most sustainable choice? The one that lasts longest with the least intervention.

WORKING WITH PERTH’S ENVIRONMENT, NOT AGAINST IT

Your deck faces challenges that indoor flooring never will. Salt, sun, rain—they’re all working to break down whatever material you choose. The question isn’t whether your deck will weather. It’s how gracefully it will age and how much effort you’ll put in to slow that process.

Smart orientation matters as much as material choice. North-facing decks in Perth cop full sun from October to March. West-facing spaces get blasted every summer afternoon. These exposures accelerate weathering by up to 40% compared to protected southern aspects.

A MORE CONSIDERED WAY TO FUND YOUR OUTDOOR UPGRADE

There’s also a quieter shift happening among Perth homeowners who want to elevate their outdoor spaces without waiting years to accumulate capital. Instead of delaying their project, they’re approaching their decking investment the same way they approach every other part of their home — with strategy.

Many are using HUMM Financing as a way to pace the spend intelligently. The deck gets built now, while shade structures, lighting or screening are added in later seasons — each stage completed when it makes the most sense for their lifestyle and cash flow.

It’s not about taking on unnecessary debt. It’s about sequencing your outdoor upgrade so you can enjoy the improvements immediately, rather than waiting for the “perfect moment” that rarely arrives. The result is a calm, measured approach: a space that evolves gracefully, and a budget that remains under control.

BEYOND MATERIAL SELECTION

The best deck for your property might not be what your neighbour installed. Your block’s orientation, your maintenance tolerance, your aesthetic preferences, and your long-term plans all factor into the equation.

That’s why we begin every deck project with a comprehensive site evaluation. We assess sun exposure, prevailing winds, soil conditions, drainage patterns, and how you actually intend to use the space.

It’s not about selling you the most expensive option. It’s about identifying the solution that will perform best on your specific block, within your maintenance comfort zone, and aligned with your investment goals.

Ready to explore what makes sense for your property? Let’s start with a design consultation that examines your site’s unique conditions, your lifestyle needs, and the real costs of each option over the next decade. We’ll help you understand not just what to build, but why it’s the right choice for your Perth home.

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