Decking done right: composite versus timber in NSW, and what it really costs

What drives the price of a deck

The boards are only part of it. Site access, height off the ground, subframe, footings, stairs, handrails, lighting, pergola integration and compliance all move the total.

Treated pine subframe with hardwood decking

$350 to $600 per m²

Treated pine subframe with composite decking

$450 to $750 per m²

Steel subframe (composite or hardwood)

add $100 to $200 per m²

Decks over 1 m high, complex shapes, steep sites

allow 15 to 30% more

These are indicative. We confirm final costs after a site visit, engineering and your chosen finishes.

What composite decking costs

Quality capped composite usually costs $150 to $250 per m² for materials, depending on brand, profile, colour and clip system. Installed on a treated pine frame, a complete build typically sits between $450 and $750 per m². Wide boards, picture framing, fascias and stainless fixings push the top end. Budget composites cost less upfront but often give up colourfastness, heat management and warranty.

• A 3.6 × 3.6 m deck (about 13 m²) at $500 to $700 per m²: roughly $6,500 to $9,000 at ground level with simple access and one stair.
• A 6 × 6 m deck (about 36 m²): roughly $18,000 to $25,000, more with a pergola roof, lighting, glass balustrade or a steel subframe.

Composite versus hardwood on the coast

• Lifespan: quality capped composite gives 25 to 30 years of structural life, with fade and stain warranties of 20 years or more. Spotted Gum or Blackbutt can also last 25 years plus with oiling and a well-detailed subframe.
• Maintenance: composite needs washing to clear salt and pollen. Hardwood needs oiling every 6 to 12 months by the ocean.
• Grip when wet: most capped composites meet P3 to P4 slip ratings. Hardwood can grip well too, but oil build-up, algae and mould reduce traction if upkeep lapses.
• Heat: darker colours get hotter in full sun. Light colours, a ventilated subframe and shade from a pergola make a big difference.
• Look: timber has a living grain and patina; composite holds its colour and clean lines.

If you love the movement and grain of Australian hardwood, timber will win your heart. If you want the same colour year after year, composite is hard to beat.

Mould, fading and what damages composite

• Mould and algae don't feed on composite but grow on dust and pollen sitting on it. Rinse routinely, scrub gently now and then, and keep airflow under the deck.
• Fading: uncapped boards fade; capped boards carry fade warranties and lighten only slightly at first.
• Damage comes from harsh solvents, abrasive scouring, hot fire pits placed on the boards, dragged furniture and blocked drainage. Use furniture pads and stainless, properly flashed fixings on the coast.

Saving money without cutting corners

• Choose standard colours and widths to avoid special orders and waste.
• Keep the footprint simple: straight runs and few angles reduce offcuts.
• Build the right subframe once: H3 or H4 treated pine, correct joist spacing, stainless screws and flashing.
• Plan pergolas and screens in the same project so footings aren't duplicated.
• Run conduits now and add lighting later.

Council approval in NSW

Some low decks are exempt development if they meet strict rules on height, size, setbacks and location. Many coastal decks are complying development or need a development application if they're elevated or attached to the house. Bushfire, flood, coastal and heritage overlays can change the pathway. We check the controls, coordinate engineering and lodge the right documents.

Does a new deck add value?

A well built deck adds usable living space, which buyers value. Composite appeals to busy households for its low maintenance; hardwood for its warmth. The best returns come when the deck is part of a wider plan with a pergola, lighting and planting.

Chris Keys and the Key Landscaping crewLandscape designers and builders on the Central Coast since 2016.