Can we stay in our Hornsby home during the extension?

Yes for most ground-floor extensions — we dust-protect the existing home, seal off the active work zone, and run utilities through. Second-storey additions are harder; you usually need to vacate 4–8 weeks during roof-off and frame stand. We plan the occupancy strategy at contract stage so you're not guessing week to week.

Can I live in my home during the extension in Hornsby?

Usually yes for ground-floor rear extensions — the existing home remains liveable with temporary weatherproofing. For second-storey additions, you may need to relocate for 4–8 weeks during the roof removal and upper-level frame phase. Buildana minimises disruption and advises on the best approach for your specific project.

Can I add a second storey to my Hornsby home?

Most single-storey homes in Hornsby can take a second storey if the existing slab and footings support the additional load. Buildana's structural engineer assesses load capacity during design. Hornsby Shire Council's height limit of 8.5–9m in R2 / R3 / R4 mixed (Hornsby CBD) zones accommodates two storeys. Second-storey additions in Hornsby typically cost $300K–$500K depending on size, access, and complexity.

Will extending my home affect my neighbours in Hornsby?

Hornsby Shire Council requires extensions to maintain solar access to neighbouring properties — typically 3 hours minimum to living areas and private open space on 21 June. Privacy measures (obscure glazing, screen planting) may be required for elevated windows near boundaries. Buildana designs around these requirements to avoid DA objections and delays.

Does an extension trigger upgrades to existing plumbing and electrical in Hornsby?

Often yes. New circuits in the extension must comply with AS/NZS 3000:2018, which usually means upgrading the main switchboard if the existing one lacks RCDs or capacity. Plumbing similarly — if the existing service is undersized for added bathrooms or kitchen, Hornsby Shire Council's certifier will require an upgrade. Buildana scopes these triggered upgrades in the contract upfront, not as variations once the wall's open.

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Home Extension Builder Hornsby — From $150K Fixed Price

Q: Does extending add equivalent value to the cost in Hornsby?

Well-designed extensions in Hornsby typically return 70–90% of cost in immediate market value uplift — and often exceed cost over a 3–5 year hold as the broader market lifts. With Hornsby medians at $1.8M–$2.6M Hornsby/Asquith/Mount Colah; $2.4M–$3.6M Cherrybrook/Beecroft/Pennant Hills; $3.0M–$8.0M+ Galston/Arcadia acreage, a $250K extension that converts a 3-bed cottage into a 4-bed family home with open-plan living usually moves the property comfortably into the next price bracket. Kitchen and bathroom quality drive most of the valuation gain.

Fixed-price home extensions in Hornsby 2077. Rear extension $150K–$300K, second storey $300K–$500K. Hornsby Shire Council approvals managed. Free site consult.

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Quick Answer

A home extension in Hornsby costs $150,000–$600,000+. Rear extension from $150K, second-storey addition from $300K. Buildana manages design, Hornsby Shire Council approvals, and construction under one fixed-price contract.

Extending Homes in Hornsby

Hornsby homeowners with 1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations-era properties are increasingly turning to home extensions to gain space without the disruption of a full move. With typical lots of 700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe), most Hornsby properties can accommodate ground-floor or second-storey extensions under Hornsby Shire Council's planning controls. Buildana manages feasibility, design, approvals, and construction for Hornsby extension projects under one fixed-price contract.

For a extension in Hornsby, the economics are the framing question. Median price $1.8M–$2.6M Hornsby/Asquith/Mount Colah; $2.4M–$3.6M Cherrybrook/Beecroft/Pennant Hills; $3.0M–$8.0M+ Galston/Arcadia acreage; build cost on 700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe) blocks scales by site conditions and specification. Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.5 to BAL-FZ on virtually all bushland-fringe (most of the LGA) ground (moderately to highly reactive clay) keeps foundations honest — $24,000–$42,000 band — and blowouts on that line are the single most common reason fixed-price contracts elsewhere don't stay fixed. Buildana itemises the slab, structural engineering, and geotech work upfront so you see the actual cost in the contract. R3 zoning in pockets of Hornsby opens up dual occupancy potential — worth exploring even if you're not initially considering it.

Buildana manages the complete home extension process in Hornsby — 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 Hornsby from $150K
Hornsby Shire Council DA and CDC approvals managed
Ground floor, rear and second-storey additions
Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.5 to BAL-FZ on virtually all bushland-fringe (most of the LGA) soil — structural engineering included
1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations-era homes assessed for extension suitability
Connect new to existing — clean, matched finish
6-year structural warranty
Free design consultation — near Hornsby station

Why Extend Your Home in Hornsby?

Hornsby is the LGA's CBD and rail interchange — Westfield Hornsby, Hornsby Hospital and the Hornsby CBD high-rise zone front the station. R3/R4 redevelopment around the CBD with surrounding 1960s–1990s brick veneer residential streets on 600–900m² R2 blocks. Hawkesbury Sandstone bedrock with rock excavation typical.

Hornsby's mix of 1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations-era housing on 700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe) blocks creates strong opportunity for property improvement. Median prices of $1.8M–$2.6M Hornsby/Asquith/Mount Colah; $2.4M–$3.6M Cherrybrook/Beecroft/Pennant Hills; $3.0M–$8.0M+ Galston/Arcadia acreage support quality build investment. Hornsby benefits from Hornsby station on the doorstep — walkable rail access lifts both rental demand and property values. 1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations-era homes in Hornsby often have good structural foundations worth building on. Extensions add living space at a fraction of the full rebuild cost. Soil conditions in Hornsby (Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.5 to BAL-FZ on virtually all bushland-fringe (most of the LGA), moderately to highly reactive) are factored into every Buildana foundation design.

Home extension builder in Hornsby — key facts

Suburb: Hornsby, NSW 2077
Council / LGA: Hornsby Shire Council (Hornsby Shire)
Primary zoning: R2 / R3 / R4 mixed (Hornsby CBD)
Typical lot size: 700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe)
Soil class: Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.5 to BAL-FZ on virtually all bushland-fringe (most of the LGA)
Median house price: $1.8M–$2.6M Hornsby/Asquith/Mount Colah; $2.4M–$3.6M Cherrybrook/Beecroft/Pennant Hills; $3.0M–$8.0M+ Galston/Arcadia acreage
Home era: 1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations
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 Hornsby — Local Context

Foundations & Slab Design for Hornsby

Hornsby's ground is moderately to highly reactive clay (Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.5 to BAL-FZ on virtually all bushland-fringe (most of the LGA)). On a 700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe) block, that translates to engineered slab work in the $24,000–$42,000 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.

Planning Controls in Hornsby

Hornsby is zoned R2 / R3 / R4 mixed (Hornsby CBD) with R3 Medium Density pockets. Hornsby Shire Council controls FSR, height limits (typically 8.5–9m), site coverage, landscaped area minimums, and setbacks. For a extension, the binding constraints on most 700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe) blocks here are: front setback (around 4.5–6m), side setbacks (1.0–1.5m articulated), rear (3–6m depending on lot depth), and landscaped area (usually 35–40%). Buildana's design team works to those numbers from the first sketch — no late re-design when council comes back with comments.

Hornsby Build Economics

Hornsby sits in the $1.8M–$2.6M Hornsby/Asquith/Mount Colah; $2.4M–$3.6M Cherrybrook/Beecroft/Pennant Hills; $3.0M–$8.0M+ Galston/Arcadia acreage price band, which is the framing for any home extension decision. On a 700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe) block here, the build-versus-buy maths usually favours extension when the existing slab and frame are sound and you only need 30–50% more floor area. Free Buildana feasibility runs the numbers against your actual block before any commitment.

Designing for the Hornsby Streetscape

Hornsby's housing stock is predominantly from the 1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations.. The local anchor is Westfield Hornsby + Hornsby Hospital + Florence Street. For a home extension, the streetscape question matters more than most builders admit — a brand-new double-storey on a street of single-storey 1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations weatherboards will draw council attention on bulk and scale, even if technically compliant. Buildana designs the front elevation to read appropriately for the street while modernising the floor plan and structure behind it. Materials palette, roof pitch, fenestration rhythm — all chosen to settle into the existing rhythm rather than fight it.

What Recent Approvals Show

Hornsby Shire Council's recent decisions for Extensions in Hornsby reveal a clear pattern — applications with proper structural engineering tied to the existing footings on Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.5 to BAL-FZ on virtually all bushland-fringe (most of the LGA) soil and clean shadow analysis to neighbours' POS are progressing without RFIs. Sloppy lodgement adds 4-8 weeks of round-trip; clean lodgement doesn't.

Builder's Take on Hornsby

Timing on Hornsby 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.

Matching brick on a Hornsby extension: 1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations brick is often discontinued. We specify a close-match or deliberately contrast with render or cladding so the extension reads as intentional, not as a failed match. Done well, an intentional contrast looks better than a forced match.

Hornsby vs Nearby Suburbs

Hornsby vs nearby suburbs — key metrics for extending.

Suburb	Median Price	Typical Lot	Soil Class	Era	Station
Hornsby2077this suburb	$1.8M–$2.6M Hornsby/Asquith/Mount Colah; $2.4M–$3.6M Cherrybrook/Beecroft/Pennant Hills; $3.0M–$8.0M+ Galston/Arcadia acreage	700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe)	Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.5 to BAL-FZ on virtually all bushland-fringe (most of the LGA)	1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations	Hornsby
Asquith2077	$1.8M–$2.6M Hornsby/Asquith/Mount Colah; $2.4M–$3.6M Cherrybrook/Beecroft/Pennant Hills; $3.0M–$8.0M+ Galston/Arcadia acreage	700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe)	Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.5 to BAL-FZ on virtually all bushland-fringe (most of the LGA)	1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations	Asquith
Wahroonga2076	$3.0M–$4.6M	800–1,500m²	Class M	1920s–1960s (heavy heritage stock)	Wahroonga
Mount Colah2079	$1.8M–$2.6M Hornsby/Asquith/Mount Colah; $2.4M–$3.6M Cherrybrook/Beecroft/Pennant Hills; $3.0M–$8.0M+ Galston/Arcadia acreage	700–1,000m²	Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.5 to BAL-FZ on virtually all bushland-fringe (most of the LGA)	1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations	Mount Colah

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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Living areas that actually connect — end of the kitchen-to-backyard detour through the laundry

New master suite on the ground floor or up top — real privacy, not a cupboard conversion

Extra bathroom finally sized for a family with teenagers

Study, rumpus or guest room — rooms with an actual purpose, not a dumping zone

Light and cross-ventilation restored — older Western Sydney homes were built sealed and dark

Outdoor alfresco tied into the kitchen — entertaining stops being a production

Rooms that flow into each other rather than branching off a dark hallway

How It Works

From First Call to Final Key

On-site assessment of your 1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations-era home in Hornsby. We check structural condition, block dimensions (700–1,200m² typical (Hornsby/Asquith/Pennant Hills/Beecroft/Wahroonga boundary/Cherrybrook); 1–5ha acreage (Galston/Berrilee/Arcadia/Forest Glen/Glenorie/Berowra Heights bushland fringe)), setback availability, and Hornsby Shire Council's DCP requirements.

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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.

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We lodge your extension approval — CDC for eligible designs or DA through Hornsby Shire Council. Full documentation including structural engineering for Class Hawkesbury Sandstone bedrock predominant (saw-cutting, rock-anchoring $30K–$120K above standard substructure) / Class M Wianamatta Shale on Cherrybrook/Beecroft ridges / bushfire-prone land BAL-12.

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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.

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Final inspection, Occupation Certificate, 6-year structural warranty. Your Hornsby home now has the space your family needs.

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Quality Promise

We extend Hornsby homes with a structural engineer on every job. Second storey, rear addition, multi-room — engineered and priced upfront.

Fixed-price extension constructionNCC 2025 and BASIX compliantFull Hornsby Shire Council complianceMatched old-to-new connectionWeekly progress updates6-year structural warranty

Cost Guide

Item	Estimated Range
Adding a master suite (1900s–1940s Federation heritage (Beecroft/Cheltenham/Pennant Hills/Wahroonga boundary) + 1960s–1990s brick (Cherrybrook/Asquith/Mount Colah/Mount Kuring-gai) + 2010s+ R3/R4 redevelopment around Hornsby/Asquith/Waitara stations Hornsby home)	$130,000 – $280,000
Kitchen/living open-out to backyard	$150,000 – $350,000
Second storey for teenagers/office	$280,000 – $550,000
Extension + bathroom (growing family)	$200,000 – $400,000
Full rear + roof tie-in (entertainer's zone)	$350,000 – $600,000

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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Headquartered in Western Sydney's Fairfield. Active across all 28 metropolitan Sydney LGAs — from Penrith to the Eastern Suburbs, the Hills to the Sutherland Shire.

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Last updated: 1 April 2026

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