Ground-floor extensions on the Northern Beaches run $4,500–$6,500 per m² in 2026. Second-storey additions are $5,500–$8,000 per m². A typical 30m² extension lands between $135,000 and $200,000 all-in. Allow 6–9 months from architect to handover.
Extensions are the job homeowners ask about most and quote on least — because the numbers feel too big to start. The good news: with the right approval path and an honest builder, a ground-floor extension on the Northern Beaches isn’t a scary number. Here’s how the costs break down in 2026.
What an Extension Actually Costs Per m²
| Type | Cost per m² | Typical 30m² total |
|---|---|---|
| Ground-floor extension (mid-spec) | $4,500–$6,500 | $135,000–$195,000 |
| Ground-floor extension (high-spec) | $6,500–$9,000 | $195,000–$270,000 |
| Second-storey addition | $5,500–$8,000 | $165,000–$240,000 |
| Load-bearing wall removal (single beam) | — | $4,500–$12,000 |
“Mid-spec” means standard double-brick or framed construction, decent windows, plasterboard, mid-range flooring and joinery. “High-spec” means architectural finishes, large glazing, polished concrete or premium timber floors, and custom cabinetry.
What Goes Into the Cost
The headline rate hides a lot. On a typical Northern Beaches extension, here’s where the money actually goes:
- Footings and slab — 8–12% of total. Sandy soils near the coast and rocky soils in the hills both add cost.
- Structural steel and framing — 12–18%. Open-plan layouts mean longer beams and more steel.
- Roofing and tie-in to the existing roof — 8–12%. Matching the existing roof line is one of the trickiest parts of any extension.
- Windows and external doors — 8–15%. Large stacker doors and bifolds add up fast.
- Services rerouting (plumbing, electrical, gas) — 6–10%.
- Internal finishes (flooring, paint, doors, skirting) — 12–18%.
- Joinery and fitouts — 8–15% if you’re including a kitchen or bathroom.
- Site costs (skip bins, scaffold, protection, certifier) — 5–8%.
- Builder’s margin and supervision — built into the rate.
Load-Bearing Wall Removal — Typical Pricing
Opening up a kitchen or living area by removing an internal load-bearing wall is one of the highest-impact, lowest-cost ways to transform a home. Numbers we see in 2026 on the Northern Beaches:
- Single PFC or UB steel beam, single storey above: $4,500–$8,000 incl. engineering certificate.
- Single beam, two storeys above: $7,500–$12,000.
- Long-span (5m+) opening with multiple supports: $10,000–$18,000.
- Add for relocating services in the wall: $1,500–$4,000.
You’ll need a structural engineer’s design (typically $800–$1,800) and a Form 16 / engineer’s certificate at completion. We coordinate this directly with the engineer — you don’t need to chase it.
DA vs CDC — Which Approval Path You Need
Approval path is the single biggest variable in extension cost and timeline. Two paths exist:
Complying Development Certificate (CDC) — under the NSW Codes SEPP. If your build meets the development standards (size, height, setbacks, etc.) and your property isn’t in an excluded zone, a private certifier can approve it in 20–40 business days. Cheaper and faster than a DA.
Development Application (DA) — through Northern Beaches Council. Required if your property is in a heritage conservation area, bushfire-prone land in certain categories, foreshore-impact areas, flood zones, or if the build doesn’t fit complying development rules. Allow 12–26 weeks for assessment, sometimes longer.
On the Northern Beaches, a lot of the older suburbs (Manly, Mosman fringes, parts of Avalon and Palm Beach, heritage pockets in Cromer and Collaroy) require DAs. A 5-minute call with a private certifier before you commit to a design saves a lot of grief.
Realistic Timelines
- Architect / draftsman design: 4–8 weeks
- Engineering and BASIX: 2–4 weeks (often in parallel)
- CDC approval: 4–6 weeks | DA approval: 12–26 weeks
- Ground-floor extension construction: 12–24 weeks
- Second-storey addition construction: 16–28 weeks
Total: 6–9 months from first architect meeting to handover via CDC. 9–14 months via DA.
5 Things That Blow the Budget
1. Asbestos in old fibro. Common in pre-1985 Northern Beaches homes. Removal by a licensed contractor adds $3,000–$15,000 depending on quantity. Always test before demolition.
2. Undersized footings on sandy or sloping sites. Engineer-designed pile footings or piers add $5,000–$25,000 vs a standard slab. Geotech reports are worth it before quoting.
3. Roof tie-in complications. If your existing roof has rotted battens, sagging trusses, or non-compliant flashings, the “simple” tie-in becomes a partial re-roof. Allow contingency.
4. Existing wiring or plumbing not to code. Once a wall’s open, the certifier may require old wiring or galvanised pipework to be brought up to current code — not just left alone.
5. Rock excavation. Common in hilly Northern Beaches suburbs. Hammer hire and rock removal can add $4,000–$15,000 to footings and services trenches.
A good builder builds 10–15% contingency into your client budget conversation up-front. If we don’t mention it, ask.
The Bottom Line
An extension on the Northern Beaches isn’t cheap, but it’s usually 30–50% cheaper than buying a bigger house in the same suburb — once you factor in stamp duty, agent fees, and moving costs. The key is getting the approval path right early and working with a builder who’s honest about what your specific block, soil, and existing structure will throw at the budget.
Want a real number for your place? See our extensions & structural steel services or get in touch — we’ll come out and give you an indicative range before you spend money on plans. If you’re also weighing up a kitchen or bathroom reno as part of the works, our bathroom renovation guide walks through what to budget separately.
Frequently Asked Questions
How much does a home extension cost on the Northern Beaches?
In 2026, ground-floor extensions typically run $4,500–$6,500 per m² for a mid-spec finish. Second-storey additions run $5,500–$8,000 per m². A typical 30m² extension lands between $135,000 and $200,000 all-in.
How much does it cost to remove a load-bearing wall in Sydney?
Removing a single load-bearing wall and installing a structural steel beam (with engineering certificate) typically costs $4,500–$12,000 depending on span, ceiling height, and whether services need rerouting. Multi-storey or long-span openings can run higher.
Do I need a DA for a home extension on the Northern Beaches?
Many compliant single-storey extensions can be approved as a Complying Development Certificate (CDC) under the NSW Codes SEPP, which is faster and cheaper than a DA. However, heritage conservation areas, bushfire zones, or foreshore-impact properties — common on the Northern Beaches — usually need a full DA through Northern Beaches Council.
How long does a home extension take?
Design and approval typically take 8–16 weeks. Construction is 12–24 weeks for a ground-floor extension and 16–28 weeks for a second-storey addition. Allow 6–9 months total from architect to handover.
What’s the difference between an extension and a renovation?
A renovation works within the existing footprint — replacing kitchens, bathrooms, or finishes. An extension increases the footprint or adds a storey, so it requires structural engineering, foundations or steel, council approval, and a connection back to the existing roof, walls, and services.
Thinking About an Extension?
We handle ground-floor extensions, second storeys, and load-bearing wall removal across the Northern Beaches. Get in touch for an honest indicative range.
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