Home Extension Builder Collaroy Plateau — From $150K Fixed Price
Fixed-price home extensions in Collaroy Plateau 2097. Rear extension $150K–$300K, second storey $300K–$500K. Northern Beaches Council approvals managed. Free site consult.
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A home extension in Collaroy Plateau costs $150,000–$600,000+. Rear extension from $150K, second-storey addition from $300K. Buildana manages design, Northern Beaches Council approvals, and construction under one fixed-price contract.
Extending Homes in Collaroy Plateau
Extension in Collaroy Plateau runs 500–800m² 1950s–1980s stock — sandstone rock excavation, ocean-view premium on eastern fall. Realistic budget $350K–$750K.
On the ground in Collaroy Plateau (2097), the practical numbers shape every home extension. Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts soil — extremely reactive clay — pushes engineered foundation work into the $45,000–$80,000 bracket on most 500–800m² blocks. R2 Low / R3 Medium (Manly, Dee Why, Brookvale, Mona Vale, Avalon town centres) / RU2 Rural Landscape (Ingleside, Terrey Hills, Duffys Forest, Oxford Falls) / E3/E4 Environmental on bushland fringe zoning under Northern Beaches Council sets the building envelope, with R3 Medium Density pockets that open up dual occupancy options on qualifying lots. Median sale price across Collaroy Plateau sits at $2.4M–$3.8M, which frames the build-versus-buy decision from the start. B-Line bus to CBD (Collaroy interchange) station services the suburb, and that proximity affects everything from rental demand to construction site access.
Buildana manages the complete home extension process in Collaroy Plateau — 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 Collaroy Plateau from $150K
- Northern Beaches Council DA and CDC approvals managed
- Ground floor, rear and second-storey additions
- Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts soil — structural engineering included
- 1950s–1980s + premium contemporary-era homes assessed for extension suitability
- Connect new to existing — clean, matched finish
- 6-year structural warranty
- Free design consultation — near B-Line bus to CBD (Collaroy interchange) 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 Collaroy Plateau?
Collaroy Plateau is the elevated suburb above Collaroy Beach — 1950s–1980s brick and contemporary on 500–800m² blocks with ocean views from the eastern fall. Hawkesbury Sandstone with rock excavation $40K–$100K typical. Quiet residential character with Long Reef Headland proximity.
Collaroy Plateau's rural-residential character and 500–800m² blocks set it apart from standard suburban development. R2 Low / R3 Medium (Manly, Dee Why, Brookvale, Mona Vale, Avalon town centres) / RU2 Rural Landscape (Ingleside, Terrey Hills, Duffys Forest, Oxford Falls) / E3/E4 Environmental on bushland fringe zoning means different controls apply — larger setbacks, on-site services, and site-specific engineering. Transport access via B-Line bus to CBD (Collaroy interchange) connects Collaroy Plateau to the wider Sydney network. 1950s–1980s + premium contemporary-era homes in Collaroy Plateau often have good structural foundations worth building on. Extensions add living space at a fraction of the full rebuild cost. Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts soil (extremely reactive) is standard for Collaroy Plateau — Buildana includes engineered slab design in every quote.
Extension is the dominant scope across most of the heritage-protected Northern Beaches village cores given heritage controls and tight 350–700m² lots — Manly, Fairlight, Balgowlah, Balgowlah Heights, Clontarf, Seaforth, Avalon, Bilgola Beach, Bilgola Plateau, Newport, Mona Vale, Collaroy, Narrabeen, Curl Curl, Freshwater, Whale Beach, Palm Beach village cores all extension-restricted territory. Federation cottage rear additions, inter-war heritage extensions, Sydney School modernist additions (Avalon/Bilgola/Whale Beach), beach-house heritage-grade work, harbour-fall heritage-grade work, Pittwater-fall heritage-grade work all common scope. Hawkesbury Sandstone rock excavation $30K–$120K on second-storey/footing-strengthening work; Class P/E alluvial soil and dewatering on lagoon-margin extensions (Narrabeen, Dee Why, Curl Curl, Manly, Mona Vale lagoon corridors). Coastal Hazard zones drive coastal-engineering reports on direct oceanfront extensions. Salt-grade specs standard on coastal-facing extensions. Bushfire-prone overlays drive specs on bushland-fringe extensions exceeding 50% original floor area — BAL-29 minimum on most acreage; sprinklered eaves and non-combustible cladding upgrades on BAL-FZ. RFS Bushfire Protection Assessment routine. Heritage Council expects retention of stained glass, timber lining boards, beach-house weatherboard cladding, slate/terracotta roofing, sandstone walling on protected streets. Tree Preservation Order strict — AS4970 root-zone protection plans routine. Acreage extensions at Ingleside, Terrey Hills, Duffys Forest, Oxford Falls run premium homestead-grade work with RFS BPA, AWTS reconfiguration. Apartment renovations on Manly Corso, Dee Why, Mona Vale, Brookvale, Wolli Creek-equivalent town-centre stock — restricted by strata bylaws, common-property approval. Realistic budget $300K–$700K for thoughtful 60–130m² addition on inland mid-tier; $500K–$1.2M on premium suburban (Balgowlah, Forestville, Frenchs Forest); $800K–$2.5M premium oceanfront/harbour-front heritage-grade work on Manly/Clontarf/Seaforth/Avalon/Newport; $1.2M–$3.5M+ heritage-grade Sydney School/Federation restoration on Palm Beach/Whale Beach/Bilgola Beach/Avalon Beach direct waterfront; $400K–$1.2M on RU2 acreage homestead extension; $200K–$500K apartment-scale.
Planning Controls — Northern Beaches Council
Northern Beaches LEP 2022 (consolidating the legacy Manly, Warringah and Pittwater LEPs) & Northern Beaches DCP. Post-2016 amalgamation LGA spanning the entire ocean-and-harbour peninsula from North Head to Barrenjoey — 252 km² with 36+ residential suburbs, four lagoons, the Garigal and Ku-ring-gai Chase National Parks, and the Pittwater estuary. R2 Low Density covers most residential streets: FSR 0.5–0.55:1, building height 8.5–9m, front setback 6–7.5m, landscaped area 40–60%, deep soil 25–35%. R3 Medium Density along Pittwater Road and around station precincts (no rail — B-Line bus equivalents at Manly, Brookvale, Dee Why, Collaroy, Narrabeen, Mona Vale interchange/terminus) permits FSR up to 0.9:1. R4 High Density and B4 Mixed Use concentrated on Manly town centre + the Corso, Dee Why town centre, Brookvale, Mona Vale town centre, Avalon village core. Northern Beaches DCP duplex minimum lot varies by precinct — 600m² (legacy Manly + Pittwater R2) to 700m² (legacy Warringah R2). RU2 Rural Landscape covers the rural acreage belt — Ingleside, Terrey Hills, Duffys Forest, Oxford Falls, parts of Belrose — restricting subdivision to 2ha+ minimum. E3 Environmental Management and E4 Environmental Living overlays on bushland-fringe lots backing Garigal NP, Ku-ring-gai Chase NP, Manly Dam Reserve and Narrabeen Lagoon catchment further restrict siting. Heritage Conservation Areas extensive — Manly heritage core (the Corso, Eastern Hill, North Head precinct), Fairlight, Balgowlah, Balgowlah Heights, Clontarf, Seaforth, Avalon village, Newport village, Mona Vale, Bilgola Beach cove, Whale Beach, Palm Beach village, Freshwater village (Duke Kahanamoku surfing precinct), Curl Curl heritage streets, Collaroy village, Narrabeen heritage streets. Aboriginal cultural heritage protocols apply across most sandstone country (extensive rock-art sites, middens, engravings) — pre-DA Aboriginal Cultural Heritage Assessment routine on bushland-fringe and waterfront sites. Tree Preservation Order LGA-wide and strict — Northern Beaches retains the most extensive remnant bushland of any Sydney LGA. Hawkesbury Sandstone soil predominant — deep rock excavation $40K–$200K+ is LGA-defining (the most rock-excavation territory of any Sydney LGA on a per-build basis). Class P/E coastal alluvial on Narrabeen Lagoon, Curl Curl Lagoon, Dee Why Lagoon, Manly Lagoon and Mona Vale Lagoon corridors — suspended slab + Class P/E footing engineering and dewatering required. Coastal acid sulphate soils (CASS) on lagoon margins drive specialist dewatering and acid neutralisation protocols. Coastal Hazard zones are LGA-defining — coastal erosion line affects Pittwater Road oceanfront properties at Collaroy, Narrabeen, Curl Curl, Dee Why, Mona Vale, Palm Beach (2016 storm event reset baselines on Collaroy/Narrabeen specifically; multiple oceanfront properties since required Council coastal-hazard reports for any DA). Bushfire-prone land overlays are LGA-defining — BAL ratings BAL-12.5 to BAL-FZ across virtually all bushland-fringe lots (Belrose, Davidson, Killarney Heights, Frenchs Forest, Forestville, Beacon Hill, Cromer, Allambie Heights, Oxford Falls, Terrey Hills, Duffys Forest, Ingleside, Bayview, Church Point, Avalon, Bilgola Plateau, Whale Beach, Palm Beach, Clareville, Newport bushland-fringe). RFS Bushfire Protection Assessment routine — non-combustible cladding, ember-screened openings, sprinklered eaves on BAL-FZ, Asset Protection Zone (APZ) 10–40m+ on most acreage. AWTS on-site sewer mandatory on RU2 acreage belt (no reticulated sewer on Ingleside/Terrey Hills/Duffys Forest/Oxford Falls). Sydney Drinking Water Catchment overlay on parts of Ingleside, Terrey Hills, Duffys Forest western edges and Pittwater foreshore — restricts AWTS dispersal field siting and adds NSW Health/WaterNSW referral. Riparian setbacks 10–60m on Narrabeen Lagoon, Curl Curl Lagoon, Dee Why Lagoon, Manly Lagoon, Mona Vale Lagoon, Pittwater foreshore, Cowan Creek tributaries, Middle Harbour and North Harbour. Foreshore Building Line restrictions on direct waterfront across Pittwater (Bayview, Church Point, Clareville, Avalon, Newport), Middle Harbour (Clontarf, Seaforth, Balgowlah Heights), North Harbour (Fairlight, Balgowlah Heights) and ocean cliffs (Manly, Freshwater, Curl Curl, Narrabeen, Mona Vale, Newport, Bilgola, Avalon, Whale Beach, Palm Beach). The LGA has no rail — B-Line bus is the primary spine (Mona Vale terminus through Warringah Mall Brookvale interchange to CBD via Mosman). Beaches Link Tunnel (under construction, opening 2028) is the LGA-defining infrastructure event — twin tunnels under Middle Harbour connecting Cammeray to Balgowlah/Seaforth with portals reshaping traffic and property values across Balgowlah, Balgowlah Heights, Seaforth, Manly Vale and Manly. Northern Beaches Hospital (opened 2018, Frenchs Forest) anchors LGA medical employment and drives granny flat hospital-staff demand on Frenchs Forest, Davidson, Allambie Heights, Forestville, Belrose. Manly Hospital site redevelopment under master plan. Mona Vale Hospital site (Northern Beaches Hospital amalgamation legacy) under redevelopment. Warriewood Valley Release Area is the LGA's only active master-planned new-release on R3/R4 medium-density 300–600m² lots. Ingleside Precinct master-plan rezoning (originally proposed for ~3,400 dwellings) under review/paused. The Corso, Manly is the heritage retail spine. Avalon, Newport, Mona Vale, Collaroy, Dee Why, Brookvale and Manly are the primary commercial centres. Premium clifftop ocean-view properties at Manly, Freshwater, Curl Curl, Avalon, Bilgola, Whale Beach, Palm Beach are among Australia's most expensive residential markets ($8M–$30M+ on Palm Beach alone).
Home extension builder in Collaroy Plateau — key facts
- Suburb
- Collaroy Plateau, NSW 2097
- Council / LGA
- Northern Beaches Council (Northern Beaches)
- Primary zoning
- R2 Low / R3 Medium (Manly, Dee Why, Brookvale, Mona Vale, Avalon town centres) / RU2 Rural Landscape (Ingleside, Terrey Hills, Duffys Forest, Oxford Falls) / E3/E4 Environmental on bushland fringe
- Typical lot size
- 500–800m²
- Soil class
- Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts
- Median house price
- $2.4M–$3.8M
- Home era
- 1950s–1980s + premium contemporary
- 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 Collaroy Plateau — Local Context
What Collaroy Plateau Soil Means for Your Extension
Most blocks across Collaroy Plateau (2097) classify as Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts — extremely reactive clay. Translation for a home extension: foundation cost lands somewhere between $45,000–$80,000, depending on building footprint and how the engineer reads the borehole. Reactive soils move with seasonal moisture. A waffle pod alone won't cut it on a Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts site — you need stiffened edge beams, sometimes piered footings, and careful detailing around wet areas to stop differential movement showing up as cracking. Buildana includes the geotech report, structural engineering, and slab design in every quote. No site allowance, no provisional sum.
Approval Timeline for Collaroy Plateau
Realistic timeline for a extension in Collaroy Plateau: 8–14 weeks for DA through Northern Beaches 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.
Realistic Budget for Collaroy Plateau
For a home extension in Collaroy Plateau, the budget conversation starts with what you actually want versus what the site supports. Most quotes you'll get from volume builders strip out the things that matter on Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts soil — engineered slab upgrade, decent waterproofing, real drainage design, BASIX-compliant glazing — and present them as variations after you sign. We don't do that. Buildana's contract is fixed-price including everything required to deliver a extension that complies with NCC 2025 on a 500–800m² block in Collaroy Plateau.
What Makes a Extension Work in Collaroy Plateau
Collaroy Plateau (2097) is part of Northern Beaches. B-Line bus to CBD (Collaroy interchange) station is the rail anchor for the suburb. Building well here means understanding what the suburb actually rewards — and what it punishes. Reward: thoughtful orientation, family-scale outdoor entertaining, durable materials that look right against the 1950s–1980s + premium contemporary streetscape, and floor plans that handle multi-generational living without feeling cramped. Punish: over-glazing on west elevations (summer heat is brutal), thin slab specs on Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts ground, generic project-home elevations that ignore the street rhythm. Buildana has built across Northern Beaches long enough to know where the line sits.
Northern Beaches Council Processing & Collaroy Plateau Activity
Northern Beaches Council processes thousands of residential applications a year across the Northern Beaches LGA, and Collaroy Plateau (2097) sits in the active end of that workload. For a home extension, the realistic clock from lodgement to DA determination is 8-14 weeks. The applications that move to the front of the queue are the ones where every required document is correctly named, drawn to scale, and matched against the SEPP or LEP clause it's claiming compliance with. Buildana lodges every project at that standard — not because it's required, but because it's how you avoid sitting in the RFI loop for an extra month.
Builder's Take on Collaroy Plateau
Northern Beaches Council setback and height rules apply to the extension, not the whole house. An older Collaroy Plateau home that was built inside the setback might not be extendable to the boundary. We check that during feasibility so there's no expensive surprise at DA stage.
Timing on Collaroy Plateau extensions typically runs 14–24 weeks for ground-floor additions, 20–32 weeks for second-storey. Living in the house during the build is possible but requires staging — we plan around it so the kitchen and main bathroom aren't out at the same time.
Collaroy Plateau vs Nearby Suburbs
Collaroy Plateau vs nearby suburbs — key metrics for extending.
| Suburb | Median Price | Typical Lot | Soil Class | Era | Station |
|---|---|---|---|---|---|
| Collaroy Plateau2097this suburb | $2.4M–$3.8M | 500–800m² | Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts | 1950s–1980s + premium contemporary | B-Line bus to CBD (Collaroy interchange) |
| Collaroy2097 | $2.8M–$8M+ (oceanfront) | 450–900m² | Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts | 1920s–1960s heritage + premium contemporary | B-Line bus to CBD (Collaroy stop) |
| Cromer2099 | $2.0M–$2.8M | 550–800m² | Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts | 1960s–1980s | B-Line bus to CBD (Brookvale interchange) |
| Wheeler Heights2097 | $2.4M–$3.6M | 500–800m² | Class Hawkesbury Sandstone predominant (deep rock excavation $40K–$150K+ on most lots) / Class P/E coastal alluvial on Narrabeen/Curl Curl/Dee Why/Manly/Mona Vale lagoon corridors / coastal acid sulphate soils (CASS) on lagoon margins / coastal hazard zones on Collaroy–Narrabeen, Curl Curl, Dee Why, Manly, Mona Vale, Palm Beach beachfronts | 1950s–1970s + premium contemporary | B-Line bus to CBD (Collaroy interchange) |
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.
Have a question about your project?
Talk to our team — free site assessment and fixed-price quote.
How It Works
From First Call to Final Key
The first job on an extension is finding out what you're extending onto. Collaroy Plateau homes from the 1950s–1980s + premium contemporary were built to different standards — we open walls, check footings, verify load paths. The existing house has to carry the new work.
⏱Design follows the existing roof. A bad extension looks like a bolt-on; a good one reads as original. Matched brickwork or contrasting render (whichever the architecture calls for), tied-in roofline, continuous flooring where it should be continuous.
⏱Construction happens while you live in the house. That means weatherproofing every night, staging the works so kitchens and bathrooms don't disappear on the same week, and keeping the site clean of debris that doesn't belong in a family home.
⏱Finish is seamless. Paint match, floor match, roofline match, brick match where possible. The only way to tell the extension is new is the date on the plans.
⏱Quality Promise
Collaroy Plateau home extension specialists: we work on your home while you live in it, weatherproof the site nightly, finish clean.
Cost Guide
| Item | Estimated Range |
|---|---|
| Simple rear extension (single wall removal, no roof change) | $102,000 – $230,000 |
| Moderate extension (multiple openings, roof extended) | $230,000 – $430,000 |
| Complex extension (structural steel portals, re-roofing) | $430,000 – $680,000 |
| Second-storey tie-in (existing house re-engineered) | $400,000 – $730,000 |
Prices are indicative for Western Sydney (2025). Actual costs depend on site, specifications, and approvals.
Our Team
Oliver Alameri
Founder / Director / Builder · MPropDev · PhD Student
Ahmad Alameri
Accounts Manager
Claire Wendell
Project Manager
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Last updated: 1 April 2026
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