Home Extensions & Additions · Sydney

More space.Without moving.

Licensed Sydney builder for ground-floor extensions and second-storey additions. We handle design, engineering, council approvals and the build — one team, one fixed-price quote, one handover.

Get an instant estimate ↓ Call 0437 477 855
NSW Lic. 393831C Family Business of the Year 2024 CDC & DA managed end-to-end 6-yr defects guarantee
Sydney home extension by Tillow Built — second-storey addition with timber detailing
$2.8k–$5.8k Sydney 2026 per-m² range
(Standard to Premium)
6–12 mo Typical extension timeline
(design to handover)
3–6 wks CDC turnaround
(Complying Development)
6 yr Major-defects
guarantee on every build
What We Build

Two ways to add space — we do both.

Whether you push out for a bigger kitchen and family room, or go up for extra bedrooms and an ensuite, we manage the full scope. Design, engineering, approvals, build, handover.

Ground-floor extensions

Push the footprint out the back, side or front. Open-plan kitchen / living additions, master suites, study or media room. Typically $2,800–$4,800 per m² depending on finish.

Second-storey additions

Add a whole new floor without giving up garden. Bedrooms, ensuite, study, retreat. Typically $3,800–$5,800 per m² — structural pre-check included before we quote.

Wrap-around & combined

Single-storey rear extension with a partial first-floor addition above. We design these to integrate with the existing home so the join doesn't read as an "extension".

Heritage-sensitive builds

Inner West conservation areas, Federation cottages, Victorian terraces. We work with heritage consultants and council planners to land DAs on character-respectful designs.

Council approvals (CDC + DA)

We manage the certifier, town planner and council liaison end-to-end. CDC for compliant designs (3–6 weeks), DA for everything else (8–16 weeks).

One-team build

Carpentry, structural, roofing, waterproofing, plumbing, electrical, plastering, tiling, painting, joinery, finishes — all under our project manager. No coordinating sub-trades yourself.

Free Instant Estimate

Try the Sydney 2026 extension cost calculator

Pick your scope — ground-floor or second-storey, area, finish tier, structural complexity, wet areas, site factors and suburb. We'll give you a real indicative range based on triangulated 2026 quantity surveyor data and our actual completed builds. No spam, no hard sell.

Open full estimator ↗ Or book a free site visit
From Idea to Handover

The 6-step extension process

A typical Sydney extension takes 6–12 months end-to-end. Here's exactly what happens at each stage so there are no surprises.

Hubert reviewing extension drawings on a Sydney balcony with a homeowner
Step 01 in action — on-site scope and feasibility walk-through with a Sydney homeowner.
01

Scoping call & site visit

30-min call to understand what you want, then we visit, measure, photograph and listen. No charge, no obligation.

Week 0–1
02

Concept design & cost feasibility

We sketch options, run preliminary cost feasibility against your budget, and identify approval pathway (CDC vs DA) and any structural risks like underpinning.

Week 2–5
03

Approval pathway & design dev

Drawings developed to certifier or council standard. Heritage consultation if needed. CDC lodged at this stage; DA goes to council.

Week 4–12
04

Engineering & fixed-price tender

Structural engineer engaged, services coordinated, all materials and finishes locked in. You get a single fixed-price contract — no provisional sums on the major items.

Week 8–14
05

Build & weekly walk-throughs

Your project manager runs the site, schedules the trades, manages quality and meets you on-site weekly. Photo updates between visits.

Week 14–36
06

Handover & 6-yr guarantee

Defects walk-through, certifier sign-off, occupation certificate, full handover pack (warranties, manuals, plumbing/electrical compliance), 6-yr major-defects guarantee.

Week 36–38
Council Approvals 101

CDC vs DA — which one do you need?

Sydney has two approval pathways for home extensions. The right one depends on your design, your block, and any heritage overlays. We'll tell you straight up at the design stage which one fits.

Faster · Cheaper

CDC — Complying Development Certificate

For extensions that comply with the NSW Housing SEPP — meeting standards on height, setbacks, site coverage, FSR (floor-space ratio), and BASIX. Issued by a private certifier, not council.

Turnaround
3–6 weeks typical
Cost
~$3,000–$6,000 (certifier + reports)
Best for
Standard ground-floor & second-storey extensions on standard blocks, no heritage, no overshadowing issues
Risk
Low — if it complies, it gets approved
Slower · More Flexible

DA — Development Application

For anything that doesn't fit the SEPP — heritage areas, oversized FSR, conservation overlays, complex sites, or council-controlled zones. Lodged with your local council.

Turnaround
8–16 weeks typical (longer for heritage)
Cost
~$6,000–$15,000 (council fees + planner + reports)
Best for
Heritage homes, non-compliant designs, complex blocks, anything ambitious
Risk
Council can require modifications — we engage a town planner upfront to de-risk
What we handle for you: certifier engagement, town planner (DA only), structural engineer, BASIX assessment, energy & thermal reports, heritage impact statement (if needed), neighbour notification (DA), build-over-sewer consent (Sydney Water), driveway crossing applications, Section 73 / 7.11 contributions. All quoted upfront — no surprises.
What Drives the Cost

Where your extension budget actually goes

Based on Sydney 2026 averages from RLB / Altus quantity surveyor data, MBA NSW, HIA NSW Cost Guide and our completed projects.

1

Floor area & finish tier

The biggest lever. Standard finishes ($2,800–$3,800/m²) vs Mid ($3,800–$4,800) vs Premium ($4,800–$5,800) makes the largest single difference. A 35 m² ground-floor extension can swing $40k–$70k between tiers.

~50% of total spread
2

Structural complexity

Second storeys often need underpinning ($1,500–$3,500 per linear metre) on older Sydney homes. Removing load-bearing walls adds steel and engineering. Complex sites can lift the build cost 5–15%.

+5% to +15%
3

Suburb & access

Eastern Suburbs, Lower North Shore and Northern Beaches typically run ~15% above the Sydney baseline (labour, parking, access). Inner West heritage pockets ~10% above. Tight access adds craneage and slower trade days.

+10% to +15%
4

Wet areas inside the addition

A new full bathroom adds $22.5k–$44k by tier. Ensuite $20k–$42.5k. New kitchen $30k–$67.5k. These are the highest-cost square metres in any extension — tile, waterproofing, plumbing, joinery, fixtures.

$20k–$70k each
5

Heritage & site factors

Conservation overlays demand matching profiles, slates, joinery details and DA conditions. Heritage typically adds 6–15% to total cost and 4–8 weeks to approvals. Sloping sites and easements stack 3–6% each.

+3% to +15%
6

2026 macro environment

Sydney building costs are tracking +4.0–4.5% YoY (RLB / Altus consensus). Copper is +16.5% YoY (electrical & plumbing). Labour shortages remain acute. Locking pricing early is worth ~3–5% on a 12-month build.

+4% per year
Recent Work

A few we're proud of.

Second-storey addition with custom timber staircase, Sydney
Custom joinery in extended kitchen / living area
Substructure / framing in progress on a Sydney extension build
Frequently Asked

Common questions about Sydney extensions

How much does a home extension cost in Sydney in 2026?

Ground-floor extensions typically run $2,800–$4,800 per m² depending on finish tier. Second-storey additions are $3,800–$5,800 per m² because of structural and crane requirements. A 35 m² mid-tier ground-floor extension comes in around $130k–$150k base cost, before wet areas, suburb premiums and site factors. Use our free instant estimator for a tailored range.

How long does a Sydney home extension take from start to handover?

Typically 6–12 months end-to-end. Design, engineering and approvals (CDC or DA) take 8–16 weeks. Build runs 12–26 weeks depending on scope. Second-storey additions usually need an extra 2–4 weeks for crane, scaffold and weatherproofing logistics.

Do I need a DA or CDC?

Most simple ground-floor extensions in Sydney can go through a Complying Development Certificate (CDC) under the NSW Housing SEPP if they meet the standards. CDC turnaround is 3–6 weeks. Anything that doesn't comply — heritage areas, oversized footprints, unusual designs — needs a Development Application (DA) through the local council, typically 8–16 weeks. We handle both pathways end-to-end.

Will I need underpinning for a second-storey addition?

Possibly. Older Sydney homes (especially pre-1970s on sandstone or fill) often need underpinning to support the extra load. It typically costs $1,500–$3,500 per linear metre. We always commission a structural pre-check before quoting a second storey — so you get a real number, not a surprise.

Can we live in the house during the extension?

For most ground-floor extensions, yes — we weatherproof the connection between the existing home and the new build so you can stay in place. For second-storey additions and major reconfigurations, you may need to relocate for 4–12 weeks during the most disruptive phase. We flag this clearly at the design stage so you can plan.

What's actually included in a Tillow Built extension quote?

A fixed-price quote covers everything: site set-up, demolition, structural engineering, footings or underpinning, framing, roofing, weatherproofing, glazing, plumbing rough-in & fitout, electrical rough-in & fitout, insulation, internal linings, joinery, painting, tiling, fittings & fixtures, flooring, certifier sign-off and handover documentation. Council/CDC fees are itemised separately so there's no markup on government charges.

Are you licensed and insured? What about HBCF?

NSW Builder's Licence 393831C, full public liability and workers compensation. HBCF (Home Building Compensation Fund) cover applies on jobs over $20,000 — we arrange that for every extension contract. 6-year major-defects guarantee on all completed work.

Why work with a builder who handles approvals end-to-end?

Splitting the design and build between separate firms is where most Sydney extensions blow out on cost and timeline — the design doesn't account for buildability or budget, and you're left negotiating change orders mid-build. Our integrated model means feasibility is checked at concept stage, the engineer talks to the carpenter, and the price you sign is the price you pay.

Where We Work

Extending homes across Sydney.

Inner City

Surry Hills · Newtown · Glebe · Leichhardt · Rozelle · Paddington · Redfern · Alexandria · Erskineville · Balmain · Annandale · Forest Lodge · Ultimo · Chippendale · Darlinghurst · Pyrmont

Eastern Suburbs

Woollahra · Edgecliff · Double Bay · Darling Point · Rose Bay · Bellevue Hill · Point Piper · Bondi · Bondi Junction · Tamarama · Bronte · Coogee · Randwick · Maroubra · Malabar · Little Bay · La Perouse

Inner West

Haberfield · Five Dock · Drummoyne · Concord · Ashfield · Summer Hill · Petersham · Marrickville · Stanmore

Lower North Shore

Kirribilli · Milsons Point · Lavender Bay · McMahons Point · North Sydney · Waverton · Wollstonecraft · Cammeray · Crows Nest · Neutral Bay · Cremorne · Mosman

Get in Touch

Ready to plan your extension?

Tell us about your home and what you're hoping to add. We'll come measure up and give you a written feasibility within 5 business days.

Call: 0437 477 855

Email: tillowbuilt@gmail.com

Servicing: Greater Sydney & Northern Beaches

NSW Licensed Builder · Licence No. 393831C · Fully Insured · HBCF cover on every job

📞 Call 0437 477 855