Licensed Home Extension Builder Double Bay
NSW licensed extension specialist. Double Bay 2028 extensions on 1900s–1940s + apartments-era homes require structural sign-off, Class M (sandstone ridges) / H–E (harbour fall) footings, and matched connection — we engineer and document properly.
HIA Member
MBA NSW0476 300 300Double Bay Home Extensions — Fixed Price
Extension in Double Bay is heritage-grade work on Federation mansions and inter-war heritage. Suspended slabs and substantial retaining on harbour-fall sites. Realistic budget $500K–$1.6M for premium 70–140m² addition. Pre-construction 9–12 months.
On the ground in Double Bay (2028), the practical numbers shape every home extension. Class M (sandstone ridges) / H–E (harbour fall) soil — extremely reactive clay — pushes engineered foundation work into the $45,000–$80,000 bracket on most 250–1,000m² blocks. R2 Low / R3 Medium / R4 / B2/B4 mixed zoning under Woollahra Municipal Council sets the building envelope, with R3 Medium Density pockets that open up dual occupancy options on qualifying lots. Median sale price across Double Bay sits at $4.5M–$15M, which frames the build-versus-buy decision from the start. Nearest rail is Edgecliff (1 km, ferry to Circular Quay), and that proximity affects everything from rental demand to construction site access.
Buildana manages the complete home extension process in Double Bay — from design consultation and structural engineering through to DA or CDC approval, and fixed-price construction to handover. Extend your home without the stress.
Read our Home Extension Cost Guide 2026 or explore extension approval pathways in NSW.
- Home extensions in Double Bay from $150K
- Woollahra Municipal Council DA and CDC approvals managed
- Ground floor, rear and second-storey additions
- Class M (sandstone ridges) / H–E (harbour fall) soil — structural engineering included
- 1900s–1940s + apartments-era homes assessed for extension suitability
- Connect new to existing — clean, matched finish
- 6-year structural warranty
- Free design consultation — near Edgecliff (1 km, ferry to Circular Quay) station
Reviewed by Oliver Alameri
Licensed Builder (NSW 487805C) · Master of Property Development · PhD Student · Building across Western Sydney since 2010
Why Extend Your Home in Double Bay?
Double Bay is harbourside premium — New South Head Road shops, Bay Street village, harbour beach. Federation mansions, inter-war flats and harbourside apartments on 250–1,000m² blocks with substantial fall to the harbour. Heritage Conservation Areas cover most streets. Sandstone-dominant soil. Premium for harbour outlook and shopping.
Double Bay's established streetscape and median house prices of $4.5M–$15M reflect a premium location within Woollahra. Building costs sit above the metro average, offset by stronger capital growth and rental returns. Transport access via Edgecliff (1 km, ferry to Circular Quay) connects Double Bay to the wider Sydney network. 1900s–1940s + apartments-era homes in Double Bay often have good structural foundations worth building on. Extensions add living space at a fraction of the full rebuild cost. Class M (sandstone ridges) / H–E (harbour fall) soil (extremely reactive) is standard for Double Bay — Buildana includes engineered slab design in every quote.
Extensions are the dominant scope across most of Woollahra — Paddington and Woollahra terraces are extension-only territory given heritage controls and tight 150–350m² lots. Federation mansion additions on Bellevue Hill and Vaucluse, sandstone terrace reconfiguration in Paddington, harbour-fall heritage-grade work on Darling Point and Point Piper. Suspended slabs, structural underpinning, rock anchoring drive cost on harbour-fall sites. Heritage Council expects retention of stained glass, cast-iron lacework, ornate plasterwork, marble fireplaces, slate roofing, sandstone walling. Realistic budget $700K–$2.5M for premium 80–150m² heritage-grade addition; $400K–$1M for terrace reconfiguration. Pre-construction 9–12 months.
Planning Controls — Woollahra Municipal Council
Woollahra LEP 2014 & Woollahra DCP 2015. R2 Low Density covers most residential streets: FSR 0.5–0.6:1, building height 8.5–9.5m, front setback 4–6m varying by streetscape, landscaped area 35–45%. R3 Medium Density along New South Head Road, Edgecliff Road and Bondi Junction fringe permits FSR up to 0.95:1. R4 High Density and B4 Mixed Use centred on Edgecliff and Double Bay village. Heritage Conservation Areas are amongst Sydney's heaviest — Paddington terraces (virtually entire suburb), Woollahra village (virtually entire suburb), Queens Park, Centennial Park and Centennial Parklands frontage, Bellevue Hill mansions, Darling Point peninsula, Point Piper peninsula, Vaucluse harbourside, Rose Bay, Watsons Bay village, parts of Double Bay. Tree Preservation Order applies LGA-wide and is enforced strictly. Substantial harbour-fall sites are the LGA's signature engineering challenge: Darling Point, Point Piper, Vaucluse, Rose Bay, Bellevue Hill north-facing slopes — suspended slabs, structural underpinning, sandstone rock excavation $25K–$80K standard, rock anchoring routine. Foreshore Building Line restricts harbourside building envelopes on most premium lots. Sydney Harbour National Park frontage at South Head (Watsons Bay) adds further heritage and ecological controls.
Home extension builder in Double Bay — key facts
- Suburb
- Double Bay, NSW 2028
- Council / LGA
- Woollahra Municipal Council (Woollahra)
- Primary zoning
- R2 Low / R3 Medium / R4 / B2/B4 mixed
- Typical lot size
- 250–1,000m²
- Soil class
- Class M (sandstone ridges) / H–E (harbour fall)
- Median house price
- $4.5M–$15M
- Home era
- 1900s–1940s + apartments
- Typical price range
- $150,000 – $600,000+
- Typical timeline
- 6–12 months design to handover
- Approval pathway
- CDC for most rear extensions, DA for second-storey
Building in Double Bay — Local Context
Foundations & Slab Design for Double Bay
Double Bay's ground is extremely reactive clay (Class M (sandstone ridges) / H–E (harbour fall)). On a 250–1,000m² block, that translates to engineered slab work in the $45,000–$80,000 bracket for a extension. Double-check any quote that doesn't itemise the slab — 'slab as per engineering' usually means the builder will hit you with a variation once the soil report comes back. We commission the geotech upfront, before pricing, so the cost in your contract reflects what your block actually needs. If your neighbour's home shows movement cracks above architraves or below window sills, that's a signal worth knowing before you finalise design — Buildana's site assessment looks at adjacent stock too.
Approval Timeline for Double Bay
Realistic timeline for a extension in Double Bay: 8–14 weeks for DA through Woollahra Municipal Council. Add 2–4 weeks before lodgement for documentation, BASIX certificate, geotech report, and survey if you don't already have one. Construction Certificate is issued separately before works commence.
What a Extension Costs in Double Bay
Double Bay's median house price sits at $4.5M–$15M. That's the number that decides whether a home extension stacks up financially. If you're spending more than 50% of $4.5M–$15M on a extension, the economics tilt toward knockdown rebuild instead. Worth running the numbers properly before locking in scope. Buildana provides itemised quotes — no provisional sums, no allowances, no "as per engineering" line items.
Lifestyle Fit in Double Bay
Double Bay has a settled residential character. Edgecliff (1 km, ferry to Circular Quay) from the nearest station. Local landmark: Double Bay Wharf & Bay Street. For families extending here, the design considerations that matter day-to-day: orientation for natural light (north-facing living wherever the lot allows), separation between adult and kids' zones, a kitchen that opens to outdoor entertaining, garage size that fits a real family vehicle plus storage, and a layout that doesn't require renovating again in 10 years as the kids grow. Buildana designs for the long arc of how families actually use a home, not just the showroom photo.
Why Some Double Bay Builds Stall
Builds in Double Bay stall for predictable reasons. Lodgement defects (missing BASIX, wrong drawing scale, undeclared overlays). Soil surprises on Class M (sandstone ridges) / H–E (harbour fall) ground when the builder didn't commission a borehole upfront. Variation creep when the contract was light on inclusions. Trade scheduling gaps when the builder is over-committed across too many sites. Woollahra Municipal Council delays when neighbour objection triggers committee review. Buildana protects against each of these at contract stage — fully documented lodgement pack, geotech in the price, itemised inclusions instead of allowances, and a tight project-manager-to-job ratio that keeps trades moving.
Builder's Take on Double Bay
Existing-structure assessment is the non-negotiable first step. Double Bay 1900s–1940s + apartments homes often have undersized footings or termite-damaged wall plates that won't carry a second storey. We check with drilled inspections before quoting — no point designing a dream that's not structurally viable.
Second storey on a Double Bay home: the existing single-storey footings usually need reinforcement, which adds $15K–$40K. The roof comes off. The house is exposed for 4–8 weeks (weatherproofed nightly). Clients often underestimate the disruption — but the result is a doubling of floor area for 50% of the cost of a rebuild.
Double Bay vs Nearby Suburbs
Double Bay vs nearby suburbs — key metrics for extending.
| Suburb | Median Price | Typical Lot | Soil Class | Era | Station |
|---|---|---|---|---|---|
| Double Bay2028this suburb | $4.5M–$15M | 250–1,000m² | Class M (sandstone ridges) / H–E (harbour fall) | 1900s–1940s + apartments | Edgecliff (1 km, ferry to Circular Quay) |
| Bellevue Hill2023 | $6M–$25M+ | 500–2,000m² | Class M (sandstone ridges) / H–E (harbour fall) | 1900s–1940s heritage mansions | Edgecliff (3 km) |
| Edgecliff2027 | $2.5M–$5M | 200–500m² | Class M (sandstone ridges) / H–E (harbour fall) | 1880s–1960s + apartments | Edgecliff (in suburb) |
| Point Piper2027 | $15M–$100M+ | 600–2,500m² | Class M (sandstone ridges) / H–E (harbour fall) | 1880s–1940s heritage mansions | Edgecliff (2 km, ferry from Double Bay) |
Median price, soil class, and lot size shape build feasibility and final cost. Buildana assesses every site against these and other constraints during the free feasibility stage.
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Quality Promise
Buildana's Double Bay home extension process: assess the existing structure, design the addition, approve, build. Fixed price throughout.
How It Works
From First Call to Final Key
Everything that has to be right before we touch the ground. On-site assessment of your 1900s–1940s + apartments-era home in Double Bay. We check structural condition, block dimensions (250–1,000m²), setback availability, and Woollahra Municipal Council's DCP requirements. Written feasibility and cost estimate provided. Designing an extension is half about the new space and half about how it joins the old one. Doorway position, ceiling height transition, floor level matching, light wells — the junction makes or breaks how the finished home feels.
⏱The Double Bay construction phase. Fixed price, programmed, supervised. We lodge your extension approval — CDC for eligible designs or DA through Woollahra Municipal Council. Full documentation including structural engineering for Class M (sandstone ridges) / H–E (harbour fall) soil, BASIX, and shadow diagrams. CC issued before works start. For ground-floor rear extensions you usually stay in the house during the build, with temporary weatherproofing at the junction wall until the new section is locked up. Second-storey additions need a 4–8 week relocation during the roof-off and frame-up phase.
⏱The job isn't done when the site's clean; it's done when you have keys, certificates and warranties. Final inspection, Occupation Certificate, 6-year structural warranty. Your Double Bay home now has the space your family needs.
⏱Our Team
Oliver Alameri
Founder / Director / Builder · MPropDev · PhD Student
Ahmad Alameri
Accounts Manager
Claire Wendell
Project Manager
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Liverpool, NSW
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Last updated: 1 April 2026
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