Composite Decking vs Timber Decking — Adelaide Comparison

The honest answer: timber looks better for the first two years, composite looks the same in year ten as year one, and the cost difference closes over a decade once you factor in maintenance.

If you’re staying in the property long-term and value low maintenance, composite. If you love the look of natural timber and don’t mind annual oiling, timber. Neither is “wrong” — the choice depends on what you’ll actually do.

Cost comparison (2026, supplied and installed in Adelaide)

Material	Per square metre	20sqm deck
Treated pine	$180–$240	$3,600–$4,800
Merbau (hardwood)	$230–$320	$4,600–$6,400
Spotted gum / blackbutt	$260–$380	$5,200–$7,600
Composite (mid-tier)	$300–$420	$6,000–$8,400
Composite (premium)	$420–$520	$8,400–$10,400

Composite costs roughly 20-50% more upfront than the equivalent-spec timber.

Lifespan and maintenance

Treated pine

Lifespan: 15-20 years in Adelaide conditions. Maintenance: annual oiling or staining is the textbook answer. In practice most owners let it weather. After 5 years it’s grey and a bit tired. After 10 years some boards need replacing. After 20 years the deck rebuilds.

Merbau

Lifespan: 25-35 years. Maintenance: annual oil to keep the warm reddish-brown colour. Without oil, weathers to silver-grey within 18 months but stays structurally sound. Splinter risk on un-maintained boards.

Spotted gum / blackbutt / hardwood Australian timbers

Lifespan: 30-40 years. Maintenance: oil annually if you want the original colour. Hardness (5+ Janka rating) means dents and scratches are rare.

Composite (Trex, Modwood, Brio, etc.)

Lifespan: 25-30 years. Maintenance: annual wash with deck cleaner. No oil, no stain, no sand. Some fading in year 1-2 then stable. Capped composite (modern formulation) handles UV and moisture better than uncapped (early-2000s formulation).

What composite is genuinely better at

• Colour stability. Year ten looks like year one (with mild fading). Timber looks ten years old at year ten — for better or worse.
• Splinter risk. Zero. Important for kids and bare feet.
• Maintenance time. A wash, a year. Versus 4-6 hours of oiling, a year.
• Termites. Capped composite is termite-proof. Hardwood is naturally resistant; treated pine needs periodic inspection.
• Pool decks. Better slip rating, better behaviour around chlorine and salt.

What timber is genuinely better at

• Look. A new merbau or spotted gum deck is more beautiful than any composite. Even comparing year-10 deck against year-10 deck, the timber has more depth.
• Repairability. A damaged board can be replaced individually and aged in. Composite repairs leave a colour mismatch.
• Recyclability. Timber composts or burns. Composite goes to landfill (or specialised recyclers, where available).
• Cost. Treated pine is the cheapest viable deck material.

Common myths

“Composite is just plastic.” Modern composites are 50-65% wood fibre and 35-50% polymer. They feel and weigh more like wood than plastic.

“Composite gets too hot.” Capped composite in dark colours runs 10-15°C above ambient in direct sun. Light colours run 5-8°C above. Timber in dark stains runs similar temperatures. Both are warm to bare feet at midday in February.

“Timber is cheaper.” Upfront, yes. Over a 20-year horizon factoring in oiling and replacement, it’s roughly even.

“Composite is maintenance-free.” It’s low-maintenance, not no-maintenance. A capping wash twice a year keeps it looking fresh.

What to avoid

• Cheap uncapped composite. Pre-2010 composite formulations (still sold cheap) absorb moisture, grow mould, and warp.
• Untreated pine. Will rot in 5-8 years in Adelaide conditions. Always specify H3 or H4 treatment.
• Mixed-tropical hardwood. “Hardwood” without species spec varies wildly in density and stability.
• Wrong fixing class. Galvanised fixings on a coastal deck — stainless 316 is the right choice.

The decision framework

• Staying 5+ years and want low maintenance: composite.
• Staying 5+ years and willing to oil annually: hardwood timber (merbau or better).
• Renovating to sell within 2 years: treated pine with stain.
• Pool deck: capped composite or stainless-fixed merbau.
• Heritage property: hardwood timber, period.

Get a free decking quote

Request a free decking quote. Tell us the timber-vs-composite preference (or “not sure”) and we’ll forward to Adelaide builders who can quote both options.