Home Extension Builder Mount Colah — Approved in 60 Days
Mount Colah 2079 extensions with tight approval timelines. CDC where eligible (~15 days), DA via Hornsby Shire Council in 40–60 days. Construction 12–24 weeks depending on scope.
HIA Member
MBA NSW0476 300 300Quick Answer
A home extension in Mount Colah 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.
Home Extension Builder in Mount Colah
A home extension in Mount Colah uses the generous bushland-suburb block — 1960s-1990s brick on 700 to 1,000m² lots where the rear wing fits easily and the Ku-ring-gai Chase edge sets the BAL frame.
The bush-backing lots get the RFS assessment, the sandstone is read before the dig, and the junctions are engineered.
At the $1.8M to $2.6M median, the wing beats the friction of upsizing on the upper North Shore fringe.
We build these fixed-price, licence HBL 487805C. Get a quote that reads the BAL and prices the test dig.
Buildana manages the complete home extension process in Mount Colah — 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 Mount Colah from $150K
- Hornsby Shire Council DA and CDC approvals managed
- Ground floor, rear and second-storey additions
- Hawkesbury Sandstone bedrock — 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 Mount Colah station
Reviewed by Oliver Alameri
Licensed Builder (NSW 487805C) · Master of Property Development · PhD Student · Building across Western Sydney since 2010
Space is never the issue
Mount Colah's blocks hold a whole wing without the yard noticing — the extension question is bushfire compliance and rock, not room.
The brick takes the additions confidently once engineered.
Bush and rock handled
BAL ratings apply on the bush-backing lots, and shallow sandstone makes a test dig worth doing before final costing.
Both are costed off the test dig, not guessed, and priced up front.
Home extension builder in Mount Colah — key facts
- Suburb
- Mount Colah, NSW 2079
- Council / LGA
- Hornsby Shire Council (Hornsby Shire)
- Primary zoning
- R2 Low Density predominant
- Typical lot size
- 700–1,000m²
- Soil class
- Hawkesbury Sandstone bedrock
- 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
- 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
Want a real number for YOUR block — not a generic estimate?
Free site assessment, fixed-price contract, line-itemised quote within 48 hours. No high-pressure sales — just a real builder talking real numbers.
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 Mount Colah 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.
How It Works
From First Call to Final Key
Free consultation at your Mount Colah home. We inspect the existing structure, check Hornsby Shire Council's controls, measure available space, and discuss what you need.
⏱Two design moves are usually on the table: match the existing house so the extension reads as original, or contrast with it so the new section is clearly modern. Both work — choice is aesthetic, and we'll show 3D renders of both before you commit.
⏱CDC (10–15 business days) or DA through Hornsby Shire Council depending on scope. Structural engineering, BASIX, and all documentation prepared and lodged.
⏱Construction phase connects new to existing — footings, frame, roof tie-in, waterproofing at junction, internal fit-out and external finish. Staged works minimise disruption to your daily routine in Mount Colah.
⏱Final inspection focuses on the integration: paint blend, flooring transitions, ceiling height, junction waterproofing, sound transmission. The extension shouldn't feel bolted on — it should feel like the house was always meant to be this size.
⏱Our Team
Oliver Alameri
Founder / Director / Builder · MPropDev · PhD Student
Ahmad Alameri
Accounts Manager
Claire Wendell
Project Manager
Estimate Your Build Cost
Use our free calculator to get an instant cost estimate for your project
Still got questions? Talk to Oliver directly.
30-min free call — bring your block, your brief, your budget. We'll map out feasibility, timeline, and realistic cost. No sales pitch.
Frequently Asked Questions
Buildana built our granny flat in just 12 weeks. Fast approvals, great communication, and a beautiful final product. Highly recommend.
Fatima Al-Rashid
Liverpool, NSW
We Build Across Sydney
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.
Last updated: 1 April 2026
Explore Related Topics
Mount Colah Extension — Free Consultation
Free design consultation for Mount Colah 2079. We'll assess your home, design the extension, and provide a fixed-price quote.
Start Your ProjectMore in Mount Colah
Other Buildana services in Mount Colah
Costs, approval pathway and fixed-price contract detail for every other build type we deliver in Mount Colah 2079. Hornsby Shire Council regulations and local controls are covered on each page.