Most decks land between about $200 and $660 a square metre supplied and installed, treated pine at the bottom, merbau in the middle, composite higher, premium composite like Trex at the top. The levers that move the number, and why an honest quote prices by the m² after a measure.
A deck is one of the more estimable jobs you can price before anyone visits. The cost is close to
linear: the deck area in m², by the board, plus what the height and the substructure underneath add.
So you do not have to wait for a measure to learn a rough number. Here is where the figures sit on the
Central Coast, supplied and installed, in 2026.
What a deck costs per m²
Cheap quote.spread joists, pads on the dirt, board not named$160 to $200/m²
Treated pine.H3 and H4 pine, concreted footings, correct joist spacing$200 to $340/m²
Merbau / hardwood.genuine merbau or spotted gum, oiling-ready finish$320 to $470/m²
Composite.genuine Modwood or Ekodeck, closer joists, no oiling$380 to $560/m²
Premium composite.genuine Trex, the coastal no-oil top of the range$470 to $660/m²
These are a guide only, not a quote. The cheap-quote row is in red for a reason. A number that low
usually means joists spread out to save on timber, footings that are pads sat on the dirt, and a board
that is never named. It is cheap because of what it leaves out.
Why the boards are only half the price
The board you walk on sets the per-m² rate: pine at the bottom, then merbau and hardwood, composite,
and premium composite at the top. But the board is roughly half the job. The other half is the
substructure underneath and the height the deck sits at. A flat ground-level pine deck over an existing
slab is one thing. A tall composite deck with a glass balustrade is another. Both are called "a deck".
They are nowhere near the same number.
What moves the number
Board and area. The two biggest levers. Treated pine sits at the bottom, then merbau and hardwood, composite, and premium composite like Trex at the top. And cost is close to linear in area, so the m² of deck is the single biggest number on the quote.
Substructure, footings and joists. What is under the boards. Deeper footings, more posts and joists spaced closer together for composite all add to the frame. The substructure is sized for the board and the height, and it is the part a cheap quote quietly skimps on.
Height and the balustrade. The higher the deck, the more load through the posts into the footings, and once it is over a metre up the NCC requires a balustrade at least a metre high. Height drives both the substructure and the rail, so it moves the number a lot.
Ledger and flashing to the house. Where the deck bolts to the house, the ledger has to be fixed and flashed so it carries the load and keeps water out of the wall. Doing that join properly costs a little more than bolting a board straight on.
Access and slope. A flat, clear backyard is quick to work; a sloping block, tight side access or a deck over a fall all mean more labour and engineering. Both are priced after the measure, never sprung on you at the end.
Approval and compliance. A larger or elevated deck may need a Complying Development Certificate or a DA, and an elevated build may need an engineer's certificate. We tell you which path your deck falls under on the quote and factor it in.
The honest comparison is not which quote is cheapest. It is which quotes price the same board, the same
area, the same height and the same footing depth. Line those up and the gap usually explains itself.
Why the substructure decides the real cost
The part you pay for twice is the part you cannot see. A deck that sags or bounces is a substructure
problem, not a board problem. We dig the footings to depth for the height and the ground, set the posts
plumb, and space the joists for the board, closer together for composite. That costs a little more than
spread joists on shallow pads, and it is the reason the deck is still flat in ten years. It is also
exactly the part we warrant.
Ask this, exactly
“Can you send the quote priced by the m², with the board and its grade named? And the footing depth, the joist spacing and the balustrade spec each on their own line?”
A working deck builder prices by the m² and names the board, the footing depth and the joist spacing. A flat round number with nothing behind it hides where the corners were cut.
How we price at Deckline
Our estimator gives you a real by-the-m² range in under a minute, before you book anyone. Then the free
site measure pins the exact figure, itemised line by line. The board and grade are named, the footing
depth and joist spacing stated, and the balustrade spec written to the NCC. You can lay it next to any
other quote and see, line for line, where the difference sits.
Watch
What a deck really costs per m²
A short walkthrough of the levers that move a deck price, so you can read a quote and tell a fair number from a vague one before you sign.
Common questions
How much does a deck cost per square metre?
As a guide most decks land between about $200 and $660 a square metre supplied and installed. Treated pine sits at the lower end, hardwood like merbau in the middle, composite higher, and premium composite like Trex at the top. A deck up high with a balustrade costs more than a low one, because of the footings, posts and rail. Our by-the-m² estimator gives you an honest range in under a minute.
Why are two deck quotes so far apart?
Usually because they are not the same deck. One names the board and its grade, the footing depth and the joist spacing. The other gives a lump sum for "the deck" and stays quiet on the substructure and the balustrade. The gap hides under the boards. Read the lines, not the total.
Can you price my deck without visiting?
We can give you an honest by-the-m² range on screen, and a tighter number from a photo. The fixed price comes after a free site measure, because the height, the ground and the balustrade change the substructure. We do not price a deck properly over the phone.
Deckline Decks