What Does a New Deck Cost on the Northern Beaches in 2026?

Most deck quotes look about the same on the cover page and very different underneath. The supply price of decking boards is roughly the same wherever you go — the difference is in the joists, footings, fixings and labour. This guide walks through what a deck on the Northern Beaches actually costs in 2026, why some quotes are 30% cheaper than others, and where the budget really gets spent.

Hardwood vs Composite Per-sqm Rates

These rates assume a deck under 1m off the ground on a relatively flat block. They include footings, bearers, joists, decking, fixings and a basic finish (oiling for hardwood, nothing for composite). They do not include balustrades, stairs over a few risers, or tying back into an existing house.

Where the Budget Actually Goes

On a typical 30sqm hardwood deck on a Northern Beaches block, the spend breaks down something like this:

• Footings (concrete piers or stirrups) — 8–12% of total. Sandy Avalon and Newport blocks need deeper piers. Rocky Seaforth blocks mean coring or hammer hire.
• Bearers and joists — 18–25%. H3 treated pine is standard; coastal builds within 1km of the surf should step up to H4 or use hardwood bearers.
• Decking boards — 25–35%. Spotted Gum 86 × 19mm runs around $14–$18 per lineal metre supplied at the time of writing.
• Fixings — 4–7%. Stainless 316 screws are non-negotiable within 1km of saltwater. Galvanised will rust through coastal hardwood inside 5 years.
• Balustrade — 10–20% if required. Stainless wire is $300–$450 per lineal metre. Glass is $550–$800.
• Stairs and trims — 5–10%.
• Labour, site costs, certifier, skip — 12–18%.

What a Cheap Quote Skips

If one quote comes in at $700/sqm and another at $1,000/sqm, look at these line items before assuming you’ve found a bargain:

• Joist spacing. 450mm max for 19mm hardwood; 300–400mm for most composite brands. A cheap quote often runs joists at 600mm centres — cheaper, but boards bow within 12 months.
• Fixing type. Galvanised vs stainless 316 is a small line item that decides whether your deck lasts 8 years or 25.
• Footing depth. A 300mm pier is cheap. A 600mm pier on sandy soil is required. Engineers spec the second; cheap builders pour the first.
• Bearer size and span. 90 × 90mm bearers at 1.8m centres is wrong on a 4m-wide deck. You need 140 × 90mm or shorter spans.
• Membrane on existing structures. If the deck is up against the house, the ledger board needs a flashing membrane behind it. Skip that and water rots the wall framing in 3 years.

Ask any builder for the joist spacing, bearer size and footing detail in writing before you sign. If they fudge it, walk.

Coastal Sites — What It Adds

Within 1km of the surf (Manly through to Palm Beach, plus Mona Vale, Newport, Avalon), salt air does work. Three things change:

• Stainless 316 fixings throughout. Adds $400–$900 to a 30sqm deck vs galvanised.
• Hardwood bearers preferred over treated pine. H3 treated pine is fine 2km inland; on the coast, hardwood lasts the distance.
• BAL ratings. Foreshore bushland zones (Bilgola, North Avalon, parts of Whale Beach) trigger BAL-19 or BAL-29 requirements — that means non-combustible decking or treated hardwood with specific spec. Adds 10–20% to material cost.

If you’re in Avalon or anywhere near the foreshore, factor coastal spec from the first conversation.

Approval Path — What Triggers a DA

Most Northern Beaches deck builds fall into one of three buckets:

Exempt development. Deck under 25sqm, under 1m above ground, set back from boundaries, not on a heritage or foreshore site. No approval needed. Most low ground-level decks fall here.

Complying Development Certificate (CDC). Larger decks, slightly elevated, on standard residential blocks. Approved by a private certifier in 4–6 weeks. Adds $1,500–$3,000 in fees.

Development Application (DA). Triggered by heritage zones, foreshore overlays, bushfire zones (BAL-29+), or non-complying setbacks. Northern Beaches Council assessment runs 12–26 weeks. Adds $3,000–$6,000 in fees and consultant reports.

Heritage pockets in Manly, parts of Avalon, and any block within the foreshore building line will usually need a DA. A 10-minute call to a certifier before you finalise the design saves real money.

The 5 Things That Blow a Deck Budget

1. Termite damage in existing structures. Tying a new deck into an old pergola or house frame — we open it up, find termite-damaged framing, and the “simple” tie-in becomes a structural repair. Allow $2,000–$8,000 contingency.

2. Sandstone underfoot. Common across the hilly suburbs. Hammer hire and rock removal for footings can add $2,500–$7,000.

3. High decks needing engineered footings. Anything over 1.5m off the ground usually needs engineer-designed footings and bracing. Adds $3,000–$8,000 over a low-set deck.

4. Existing concrete that’s the wrong height. If you’re decking over an old slab, the slab height and fall determine whether you can build a low-profile deck or whether you need to demo first. Demo and re-pour: $4,000–$10,000.

5. Stair runs over 1m total rise. Triggers handrail compliance, going/rise calculations and sometimes a landing. Adds $1,500–$3,500 vs a simple two-tread step.

Realistic Timelines

• Design and quote: 1–2 weeks
• Approval (if required): 4–6 weeks CDC, 12–26 weeks DA
• Lead time on materials: 2–4 weeks for hardwood, 1–3 weeks for composite
• Build (30sqm low deck): 7–12 working days on site
• Build (50sqm with balustrade and stairs): 14–20 working days

From signed quote to standing on the deck: 3–5 weeks if exempt, 8–12 weeks if CDC, 4–7 months if DA.

What to Ask Before You Sign

• Joist size, joist spacing, bearer size, bearer span — in writing.
• Fixing type (stainless 316 for coastal).
• Footing type and depth, signed off by an engineer if elevated.
• Whether the price includes balustrade, stairs, and tie-in to the house.
• What’s NOT included (this is where surprises live).
• Insurance certificates (Home Building Compensation Fund cover for jobs over $20k in NSW).

The Bottom Line

A well-built 30sqm hardwood deck on the Northern Beaches in 2026 costs $25k–$36k. A composite version of the same deck costs $36k–$50k. Cheaper quotes exist; they’re cheaper because something is missing. Read the joist spacing line, the fixing line, and the footing line before you read the total.

For a deeper material comparison, see our guide on hardwood vs composite decking. If you’re ready for a real number on your block, see our decks & outdoor living service page or get in touch.

Frequently Asked Questions