Composite vs Timber Decking in Australia: Cost, Lifespan and Which to Choose

Last updated: 7 July 2026 · By Mossy Tariq, Founder — Property Blueprint Co.

The decking material comparison almost every homeowner runs is the wrong one. They compare the price per square metre of composite against the price per square metre of timber, and composite loses that comparison every time. The comparison that actually decides the outcome is the cost per square metre per year the deck is in service — and on that measure, the two materials are far closer than the sticker price suggests, and the winner depends on which timber is being compared.

This is the same distinction that runs through every materials decision in a renovation — the reason outdoor renovation quotes lead with the visible surface layer and bury the layers that actually decide the total. Decking is priced the same way: the board cost is what gets quoted, and the twenty-year cost is what actually happens.

Every figure below is sourced to Australian decking industry cost data and cross-checked against timber durability classifications and Bushfire Attack Level (BAL) construction requirements. What follows is what composite and timber decking actually cost in Australia in 2026, how long each genuinely lasts, and which one is the right call for a specific block.

The deck that costs less to build is not always the deck that costs less to own.

What is the real cost difference between composite and timber decking in Australia

Timber decking typically costs $120 to $250 per square metre installed for softwood species like treated pine, rising to $250 to $450 per square metre for hardwoods such as merbau and spotted gum. Composite decking sits at $250 to $450 per square metre installed — meaning composite and hardwood timber start at almost the same price point, and the real comparison most homeowners should be running is composite versus hardwood, not composite versus pine. What sits inside those installed figures — subframe, labour, height, and the approval and bushfire costs on top — is broken down in how much decking costs in Australia.

Board material alone, before subframe and installation, narrows the gap further: composite board typically runs $100 to $170 per square metre depending on quality tier, against $60 to $180 per square metre for timber depending on species. The build cost is genuinely close. The difference that matters shows up after handover, not on the day the invoice is issued.

Which timber species actually compete with composite on lifespan

Three timber species carry most of the credible case for timber over composite in Australia, and the rest of the market — treated pine especially — does not genuinely compete on lifespan at all.

1. Merbau. A Class 1 durability hardwood rated for above-ground use, with a density around 830kg/m³ that resists scratching and denting. A well-installed, well-maintained merbau deck can run 25 to 40 years — genuinely overlapping composite's lifespan at the top end. Merbau is also rated for Bushfire Attack Level (BAL) 12.5, 19, and 29 zones without additional chemical treatment, which matters in fire-prone regions.
2. Spotted gum. Also Class 1 durability, commonly exceeding 30 years with proper maintenance, and carries lower tannin bleed than merbau — a practical detail that matters on a deck near a pool or light-coloured paving. Spotted gum is also approved for BAL-29 zones when it meets thickness requirements.
3. Treated pine. The cheapest timber option at $185 to $250 per square metre installed, but it is the species that makes "timber" look bad in a lifespan comparison. Treated pine typically needs oiling every 12 to 18 months and does not carry the bushfire-resisting timber classification the two hardwoods above do — it is not a genuine long-term competitor to composite, and comparing composite against pine rather than against hardwood is the comparison that produces a misleading result.

The species comparison matters because "timber decking" is not one material with one lifespan — it is a category spanning a 15-year softwood deck and a 35-year hardwood deck, and the choice inside that category moves the comparison against composite more than the choice between composite and timber does.

How does the maintenance bill change the true cost over 20 years

This is where composite pulls ahead of every timber species, hardwood included. Timber — even Class 1 hardwood — requires periodic oiling, staining, or sanding to hold its finish and slow weathering, at a typical cost of $30 to $80 per square metre per treatment. Softwood needs this every 12 to 18 months; hardwood stretches the interval further but does not eliminate it. Composite requires an occasional wash with soap and water and nothing else.

Run the maintenance line over 20 years and a pine deck that cost $5,550 to install can add another $5,000 to $8,000 in maintenance across that period — more than doubling its lifetime cost. A hardwood deck fares better than pine but still carries a genuine, recurring maintenance bill that composite does not. Industry cost analysis puts the typical break-even point between composite and timber at year five to year seven once maintenance is counted, with composite saving an estimated $4,000 to $16,000 over 20 years depending on the timber species it is compared against.

The practical detail most comparisons miss: the maintenance bill is not optional insurance. A hardwood deck left unmaintained does not fail gracefully — it silvers, cups, and splits years earlier than its rated lifespan, because the "25 to 40 years" figure for merbau assumes the maintenance schedule was actually followed, not skipped.

Does bushfire risk decide the material for you

In some postcodes, yes — the Bushfire Attack Level (BAL) rating of the site removes some options from the table before cost or lifespan enters the decision at all. In BAL-12.5 to BAL-29 zones, any timber used within 400mm of the ground or an external horizontal surface such as a deck must be a certified bushfire-resisting timber or a non-combustible material. Merbau, spotted gum, blackbutt, ironbark, and a small list of other native hardwoods carry that classification; treated pine and most softwoods do not, without additional certified treatment.

Composite decking's position here depends on the product — check the specific manufacturer's BAL compliance documentation rather than assuming composite is automatically compliant, because formulations vary. For a BAL-29 or higher site, the shortlist narrows fast: a certified bushfire-resisting hardwood or a BAL-rated composite product, with the decision then coming down to the cost and maintenance trade-off covered above rather than to the fire rating itself.

Where does composite lose to timber

Composite is not the unconditional winner the maintenance-cost comparison makes it look like. Three genuine trade-offs favour timber, and a prepared homeowner should weigh them rather than default to composite on cost-per-year alone.

Surface heat. Darker composite boards can run noticeably hotter underfoot than timber in direct summer sun — a real comfort issue around a pool or in northern Australia, and one that varies significantly by product colour and formulation.

Repairability. A damaged timber board can be sanded, oiled, or in the worst case replaced as an individual board that blends with the rest of the deck once weathered. A damaged composite board is typically replaced outright, and matching an aged composite board's colour years later is harder than matching timber, which weathers toward a similar grey regardless of species.

Resale perception. Hardwood decking — merbau and spotted gum especially — still reads as a premium natural-material choice to many buyers, where composite reads as durable but manufactured. This is a genuinely subjective factor, but it shows up in agent feedback often enough to be worth naming rather than ignoring.

How do you decide between composite and timber for your own deck

Start with the site, not the material. Confirm the BAL rating first — it may narrow the field before anything else is weighed. Then decide how the deck will be used: a shaded, low-traffic deck favours whichever material looks better to the homeowner, since the maintenance and lifespan gap matters less over lighter use. A full-sun, high-traffic, near-pool deck is where composite's low-maintenance case is strongest and where dark-coloured composite's heat trade-off needs the most attention.

The free Renovation Cost Calculator gives you a trade-by-trade estimate in under 5 minutes — before your first trade conversation — built around the surface, structure, and services layers that make up an outdoor renovation, whichever decking material is selected. That number becomes the benchmark every quote that follows is measured against.

Use the free Renovation Cost Calculator →

Where a decking decision fits inside an outdoor renovation

Decking is one surface inside a larger sequence of decisions — earthworks, structure, surfaces, services, and finishes — and getting the material choice right does not protect the budget from the other four layers going wrong. The Outdoor Renovation Blueprint covers the full twelve-phase sequence an outdoor project moves through, with the decking material decision sitting inside design finalisation, priced against the site's BAL rating and the household's actual use pattern rather than against a showroom sample.

Frequently asked questions

Is composite decking cheaper than timber decking in Australia?

Not always, and the answer depends on which timber it is compared against. Composite decking typically costs $250 to $450 per square metre installed — close to hardwood timber such as merbau or spotted gum at $250 to $450 per square metre. Composite is genuinely more expensive than softwood options like treated pine, which runs $120 to $250 per square metre, but the comparison changes once maintenance costs are added over the deck's lifespan.

How long does composite decking last compared to timber?

Composite decking typically lasts 25 to 30-plus years with a matching manufacturer warranty. Timber lifespan depends heavily on species: Class 1 hardwoods like merbau and spotted gum can last 25 to 40 years with proper maintenance, while softwoods such as treated pine typically last 15 to 20 years and require oiling every 12 to 18 months to reach even that.

Does composite decking cost more over its lifetime than timber?

Usually not. Industry cost analysis puts the break-even point between composite and timber at roughly year five to year seven once maintenance is included, with composite saving an estimated $4,000 to $16,000 over 20 years depending on the timber species compared. A pine deck costing $5,550 to install can add $5,000 to $8,000 in maintenance costs over 10 years — more than doubling its lifetime cost — while composite typically requires no chemical maintenance beyond washing.

Can you use timber decking in a bushfire zone in Australia?

Yes, but only certain species. In Bushfire Attack Level (BAL) 12.5 to BAL-29 zones, any timber within 400mm of the ground or an external horizontal surface like a deck must be a certified bushfire-resisting timber or non-combustible material. Merbau, spotted gum, blackbutt, and ironbark are recognised bushfire-resisting timbers and are approved for use up to BAL-29 when they meet thickness requirements. Treated pine and most softwoods do not carry this classification without additional certified treatment.

Which timber species lasts as long as composite decking?

Merbau and spotted gum come closest. Both are Class 1 durability hardwoods that can exceed 25 to 30 years with correct installation and a maintained oiling schedule, genuinely overlapping composite's typical 25 to 30-plus year lifespan. Treated pine and other softwoods do not compete on lifespan, typically lasting 15 to 20 years even with regular maintenance.

Does composite decking get hotter than timber in summer?

Often, yes, particularly darker-coloured composite boards in direct sun, which can run noticeably hotter underfoot than timber. This varies significantly by product formulation and colour, and is worth checking against the manufacturer's specifications before installing composite around a pool or a north-facing deck used barefoot in summer.