If you've had two or three quotes come back for what feels like the same deck and the numbers are miles apart, you're not imagining it. Timber decking is one of the most variable jobs in home improvement — and most of that variation comes down to five factors most homeowners never get asked about upfront.
1. Timber species
This is usually the single biggest swing in price. Treated pine is the budget option and holds up fine for a straightforward backyard deck, but it won't have the depth of colour or longevity of a hardwood. Merbau is the most common mid-to-upper choice in Sydney — good natural durability, a warm colour, and it's readily available. Spotted gum and blackbutt sit above that again, prized for their look and strength, but you'll pay for both the timber and the extra care needed to work with it.
As a rough guide, moving from treated pine to merbau can add 30–40% to your material cost alone. Moving to spotted gum can add more again.
2. What's underneath the boards
The substructure — bearers, joists, footings — is invisible once the deck is finished, but it's often close to half the total job cost. A deck built on a slope, over uneven ground, or requiring engineered footings because of soil conditions will cost noticeably more than one built on flat, stable ground at an easy height. If your quote seems low compared to others, it's worth asking specifically what's been allowed for in the substructure — that's usually where corners get cut.
3. Size and shape
Obvious, but worth saying plainly: cost doesn't scale in a straight line with square metres. A simple rectangular deck is the cheapest shape per square metre to build. Add curves, multiple levels, built-in seating, or a wraparound shape and you're adding labour time that doesn't show up as "extra materials" on a quote — it shows up as extra days on site.
4. Site access
A deck built where a ute can back straight up to the work area is a different job to one where every board and bag of concrete has to be carried down a side path or through the house. Tight access is one of the most under-discussed cost drivers in decking quotes — and one of the most common reasons a "surprise" comes up mid-job if it wasn't properly scoped at the start.
5. Council approval
Not every deck needs council approval, but height, size, and proximity to boundaries can trigger it. In NSW, decks over a certain height off the ground, or those attached to the dwelling above a certain size, often need a Complying Development Certificate or full DA. This adds both time and cost before a single board is laid — factor it in when you're comparing timelines, not just prices.
What a realistic budget looks like
For a straightforward, ground-level treated pine deck around 20–25m² with easy access, many Sydney homeowners see quotes from roughly $6,000–$10,000. Move up to merbau, add a step-up height or a slope, and $12,000–$18,000 is common. Larger, multi-level, or hardwood decks with tricky access can run well beyond that.
Frequently asked questions
Is treated pine actually worth using?
For a lot of backyards, yes. It's stable, cost-effective, and takes stain or paint well. The main trade-off is appearance and lifespan compared with hardwood — treated pine typically needs re-coating more often to stay protected.
How long does a standard deck build take?
A straightforward deck with good access is often 3–6 working days from footings to finished boards. Add time for council approval if it's needed, and more again for staining and curing before it's fully weather-ready.
Do I need a permit for a small deck?
Often not, if it's low to the ground and detached from the house — but this varies by council and by exactly how the deck is attached and how high it sits. It's worth a five-minute check before committing to a design.