Most Sydney homeowners don’t want to move. They want more space. An extra bedroom for a growing family. A kitchen that fits how you live. A home office that isn’t the dining table. If that sounds familiar, a home extension is almost always the smarter answer.
Moving can solve those problems, but it also comes with stamp duty, agent fees, legal costs and the challenge of finding another property in the same area. A well-designed extension often delivers a better outcome while allowing you to stay in the suburb you already love.
Double Diamond Construction are the home extension builders in Sydney who make it happen without the stress. Our experience extends beyond renovations. As builders who also construct new homes, duplexes and major residential projects, we understand structural requirements at a deeper level.
We manage the entire process from design consultation, council approvals, structural work, to final handover, under one roof, with a dedicated project manager and fixed pricing from day one.
Types of Home Extensions We Build in Sydney
Different homes need different solutions. We build across the full range of extension types, so whatever your block, your budget, or your brief, there’s an approach that works.
Rear Ground Floor Extensions
A rear extension Sydney project is one of the most popular ways to add living space without changing the street frontage of the home. A rear ground-floor extension opens up the back of your home, typically adding a larger kitchen, open plan living and dining area, or a new bedroom. It works especially well on standard suburban blocks where there’s usable rear yard space.
Second Storey Additions
Where the block doesn’t allow for a ground-floor extension, building up is the answer. A second-storey addition in Sydney adds two to four bedrooms, a bathroom, and a living area, roughly doubling your home’s footprint without touching the yard. Many Sydney homeowners choose this option because it allows them to remain on their existing block while significantly increasing the size of their home.
Side Extensions and Home Additions
Not every project involves a major expansion. A home addition Sydney project may involve extending a single room, adding a new wing to the home or improving functionality through a combination of extension and internal reconfiguration. A side addition can add a bedroom, bathroom, or connecting hallway without impacting the main backyard.
Open plan reconfigurations
Sometimes the extension is less about adding square metres and more about how they connect. We remove walls, relocate services, and rebuild layouts so the extension and the existing homework as one rather than looking like two different projects joined together.
How Much Does a Home Extension Cost in Sydney?
Cost is often the first thing homeowners want to understand, and for good reason. A home extension is a significant investment. The size of that investment depends on several factors, including design complexity, site conditions, structural requirements, access, finishes and services.
A home extension in Sydney costs between $150,000 and $400,000 or more, depending on the scope, size, and finish level. Here’s a rough breakdown by extension type:
- Rear ground floor extension (30-60m²): $150,000-$250,000
- Second storey addition (full floor): $250,000-$400,000+
- Side addition or single room: $80,000-$150,000
- Open plan reconfiguration with structural work: $60,000-$120,000
These are starting ranges. Your final cost depends on your site conditions, the complexity of structural work, the council area, and material selections.
Several factors can influence cost:
- Existing structural conditions
- Site access restrictions
- Sloping land
- Heritage requirements
- Plumbing and electrical upgrades
- Material selections
- Council requirements
Homeowners often compare extension costs against relocating. Once stamp duty, agent commissions, removalist expenses and legal fees are factored in, extending can represent better value. The benefit of extending is that you’re investing directly into a property and location you already know.
Double Diamond Construction provides fixed-price contracts wherever possible. We believe homeowners should have a clear understanding of costs before construction begins.
Our Home Extension Building Process – Step by Step
Many homeowners have never undertaken a major construction project before. A clear process helps remove uncertainty and keeps projects moving in the right direction. We manage everything from initial design through to final handover. Your project stays with the same dedicated project manager throughout.
Step 1: Initial Consultation and Site Assessment
We start by understanding what you need, what your block allows, and what a realistic budget looks like. We inspect the property, identify site constraints and assess what is realistically achievable. You get a straight-talking assessment before anything is committed.
Step 2: Design Development and Documentation
Once the project brief is established, we work with designers and consultants to develop plans that suit the property and comply with planning requirements. This stage involves refining layouts, room sizes and structural considerations. Our team prepares architectural drawings and structural documentation tailored to your site.
Step 3: Council Approval (DA or CDC)
We determine the right approval pathway for your project and manage the entire process. We guide homeowners through this process and coordinate the required documentation. We have worked across all Greater Sydney council areas and know exactly what each one requires.
Step 4: Construction Planning
Before work begins, construction schedules, material selections and site logistics are organised. Detailed planning helps reduce delays once construction starts.
Step 5: Construction
Construction generally progresses through demolition where required, site preparation, foundations, framing, roofing, external works, internal fit-out and final finishes. Your dedicated project manager coordinates all trades on site. Timelines are locked in from the start. You get regular updates and always know where the build is up to.
Step 5: Handover
Before you get the keys to your extended home, we do a thorough walkthrough inspection. Everything is checked and signed off properly.
Do You Need DA or CDC Approval for a Home Extension in Sydney?
Most home extensions in Sydney require either a Development Application (DA) or a Complying Development Certificate (CDC) before construction can begin. Which one applies to your project depends on your block size, zoning, and the scale of the extension.
CDC Approval
A CDC is faster, typically four to eight weeks and is assessed by a private certifier rather than your local council. Your extension qualifies for CDC if it meets the standard requirements set out under the NSW State Environmental Planning Policy (Exempt and Complying Development Codes). Most straightforward rear and side extensions on standard residential lots go this route.
DA Approval
A DA is lodged directly with your local council and typically takes three to six months, sometimes longer in busy council areas. It’s required when your proposed extension doesn’t meet complying development standards. For example, if it exceeds height limits, sits on a heritage-listed or flood-affected site, or if your council area has specific overlay controls.
Other factors that may influence approval requirements include:
- Heritage restrictions
- Lot dimensions
- Site coverage
- Building setbacks
- Environmental considerations
- Local planning controls
Double Diamond manages the full approval process regardless of which pathway applies. We have delivered DA and CDC home extension approvals across all Greater Sydney council areas. You don’t need to navigate the NSW Planning Portal or your Local Environmental Plan on your own.
Why a Second Storey Addition Could Be Your Best Option
Sydney’s median house price sits above $1.5 million. Buying a bigger home means stamp duty, selling costs, moving costs, and a bigger mortgage. For most families, building up is significantly cheaper than buying up.
A second-storey addition typically adds two to four bedrooms, a full bathroom, and a living area. Total cost: $250,000-$400,000, depending on design and finish. Compare that to the cost of upgrading to a larger property in the same suburb; the numbers usually aren’t close.
There’s also the block size question. Many Sydney blocks, particularly in the Inner West, North Shore, and Eastern Suburbs, don’t offer enough rear yard space for a meaningful ground-floor extension. A second-storey addition solves this by using the footprint you already have.
Double Diamond’s experience across full new home builds means we understand what a second storey requires structurally. We assess your existing foundations and structure honestly, design the addition to integrate properly with your existing home, and build it to last.
Sydney Suburbs We Build Home Extensions In
We deliver home extensions and house extension builds across Greater Sydney, including:
Inner West
- North Shore
- Eastern Suburbs
- Hills District
- Parramatta
- Liverpool
- Blacktown
- Canterbury-Bankstown
- St George
- Western Sydney
Our familiarity with local councils, planning controls and building requirements helps projects move through approvals more efficiently. Not sure if we cover your suburb? Call us on 1300 659 393.
Why Sydney Homeowners Choose Double Diamond
There’s no shortage of builders in Sydney who will tell you they do extensions. The difference is in how a project is managed once it starts. Because building an extension requires more than good construction skills.
Double Diamond Construction provides end-to-end project management from the initial consultation through to final handover. Our 15 years of experience across new home construction give us a strong understanding of structural integration. That matters because extensions need to function as part of the original home rather than appearing disconnected from it.
What clients consistently come back to:
- Fixed, transparent pricing: Our quotes are detailed and firm. If something changes, you hear about it before it costs you anything.
- One dedicated project manager: Assigned from day one through to handover. One person who knows your project, your brief, and your timeline.
- End-to-end management: Design, approvals, construction, and handover are managed as one process, not handed off between firms.
- Structural expertise: We build full new homes and duplexes, not just extensions. That structural depth shows in the quality of every home addition we deliver.
- Reliable communication: You always know where your project is up to. Our Google reviews say it consistently because communication is what made the difference.
Get Your Free Home Extension Design Consultation
If you’ve been thinking about a home extension in Sydney, the best first step is a conversation. We’ll look at your block, talk through what you’re trying to achieve, and give you a straight-talking assessment of what’s possible and what it’s likely to cost.
No pressure. No obligation. Just an honest picture of your options from home extension builders in Sydney who have been delivering this work for over 15 years.
Call 1300 659 393, email info@doublediamondconstruction.com.au, or fill in the contact form to request your free consultation.
Frequently Asked Questions
Timeline depends on the extension type and approval pathway. A straightforward rear ground-floor extension with CDC approval typically takes four to six months from approvals to handover. A second-storey addition runs six to ten months. We give you a realistic schedule from the initial consultation and manage trades to keep it on track.
For most ground-floor extensions, you can stay in the home during construction, though there will be disruption, particularly while structural work is underway. Second-storey additions often require a temporary relocation for part of the build. We discuss this clearly at the design stage so there are no surprises.
A rear ground-floor extension adds space by pushing out the back of your home at ground level. A second-storey addition builds upward, typically adding bedrooms, bathrooms, and a living area on a new upper level. Which suits your home depends on your block size, zoning, and what you need the extra space for.
In most cases, yes, particularly when the extension adds functional space like bedrooms, bathrooms, or a larger open-plan living area. The actual value uplift depends on your suburb, your existing home, and the quality of the build. CoreLogic data consistently shows that well-executed extensions in Sydney’s established suburbs deliver strong returns.
Yes. Double Diamond Construction is a fully licensed NSW residential builder. All structural work, plumbing, electrical, and other licensed trades are carried out by qualified tradespeople working under our licence and supervision.
Some projects can be approved through a CDC home extension Sydney pathway if they meet specific planning requirements. Others require a DA home extension in Sydney application through the local council. The approval pathway depends on factors such as the property, extension design, setbacks, heritage restrictions and local planning controls.
Double Diamond Construction delivers a range of home extensions Sydney homeowners require, including rear extensions, ground floor extensions, second-storey additions, side extensions, open-plan living extensions and complete home addition projects. Every extension is designed around the property’s layout, planning requirements and the family’s needs.
