An Architect’s Guide to Designing, Renovating and Extending a Home in Sydney

Sydney's homes are shaped by some of the most varied and complex conditions of any Australian city.

Heritage overlays, sloping sites, tight urban blocks, coastal exposures and complex planning controls all influence what is possible before a single design decision is made.

The residential projects we undertake at Sam Crawford Architects involve significant changes to existing houses through renovations and extensions, or a combination of both, as well as designing homes from the ground up. In every case, the process begins with understanding what a particular client needs from a specific site.

This guide addresses the most common questions homeowners ask when renovating, extending or designing a new home in Sydney and NSW, from early thinking and planning controls through to cost, processes, and what to expect when working with an architect. Consider it the groundwork for everything you should know before the first wall goes up.

Getting Started

When to Engage an Architect on a Residential Project

When beginning a new residential construction or renovation project, engage an architect as early as you can. Ideally, before you finalise a budget or speak to a builder. You may consider seeking advice even before purchasing a site. While having a budget in mind is useful, an architect can also assist you in developing one that meets your brief.

The earlier an architect is involved, the greater their capacity to shape a considered outcome. Once a site is purchased, a budget is committed to, or a builder briefed, certain decisions become difficult to revisit. This holds whether you are renovating an existing home, adding an extension, or building from the ground up.

The right time to make contact is when you are still forming questions rather than making decisions. That might be when you are considering a property and want to understand what is feasible, or when you are ready to think seriously about what your existing home needs.

Engaging late rarely saves time or money. Depending on the project, it risks:

• A brief that fails to account for site constraints: planning overlays, easements, slope, solar orientation or neighbour considerations
• A brief that does not reflect what the budget will support
• Design assumptions that unravel once planning controls are fully understood
• Builder quotes that exceed expectations because the scope was not clearly defined
• Missed opportunities to improve light, layout or orientation before the design is resolved

For heritage properties, early engagement is especially important. Conservation area requirements and council pre-consultation need to be worked through before design decisions are made.

An initial conversation costs nothing and will assist in developing a clearer picture of what is possible before any significant commitment is made.

What to Prepare Before Your First Conversation With an Architect

You do not need everything on your project resolved before the first conversation with an architect. Most architects expect to help you refine your thinking, not receive a finished brief. That said, coming prepared makes the conversation more useful for everyone.

It helps to bring what you can of the following:

• Your goals: what you want to achieve and how the space will be used day to day.
• Your budget: even a broad range gives the architect something to work with and helps avoid misaligned expectations early on.
• Your timeline: whether you have flexibility or are working toward a fixed date.
• Site information: property address, lot dimensions, any survey plans, known easements or covenants.
• Heritage status: whether the property is heritage-listed or sits within a conservation area.
• Strata or title information: relevant if the property has shared boundaries or is part of a strata scheme.
• Any previous DA applications or council correspondence relating to the property
• Design references: images, examples or simply a description of what appeals to you.

If you are renovating or extending, any existing drawings of the home are worth bringing along. The first conversation is as much about fit as it is about information. Your goals, budget and timeline are the most important starting points. The remaining items will become relevant as the project develops. Come with honest questions and an open mind.

Planning and Design Fundamentals for Renovating or Building a Home

Understanding What's Possible on Your Sydney or NSW Site

What Can You Build on Your Site?

What you can build on a residential site in NSW depends on a combination of factors specific to your site and its location. There is no single answer, but there are clear places to look.

The starting point is your zoning under the relevant Local Environmental Plan (LEP). A Section 10.7 Planning Certificate, which should have been provided with your contract of purchase or can be obtained from your council, will give you a high-level overview of the LEP and any applicable DCP requirements. 

In Sydney, residential zones broadly fall into low density (R2), medium density (R3) and high density (R4) categories, each permitting different building types, heights and site coverage. Across NSW, the same zoning framework applies, though the specific rules vary significantly between councils and regions. Your local council's LEP and Development Control Plan (DCP) set out the controls relevant to your property.

Beyond zoning, a range of other controls shape what is possible:

• Height limits: typically between 8.5m and 9.5m for low-density residential in Sydney, though this varies considerably by council area across NSW.
• Floor space ratio (FSR): limits the total floor area relative to the site area.
• Setbacks: minimum distances from boundaries and the street.
• Site coverage: the proportion of the site that buildings and structures can occupy.
• Slope, drainage and vegetation: physical site conditions that influence what is buildable.
• Heritage overlays or conservation area controls: which restrict certain changes.
• Biodiversity or bushfire overlays: relevant for properties in or near bushland.

The most reliable starting point is the NSW Planning Portal, which shows zoning and overlays for any address across the state. An architect familiar with your local council can then interpret what those controls mean in practice for your specific site and intentions.

How Zoning and Planning Controls Affect Your Project

Zoning and planning controls shape what is possible on your site before a single design decision is made. Whether you are building new, renovating, or extending, these rules define the boundaries within which any project must operate.

Zoning determines how land is categorised and what can be built on it. For instance, a residential zone permits houses; an industrial zone does not. Planning controls then set the specific rules that govern how buildings on that land are designed and built. In NSW, these rules are set out in two key documents: the Local Environmental Plan (LEP) and the Development Control Plan (DCP).

• The LEP: sets your zoning, height limits, floor space ratio, lot size requirements, etc.
• The DCP: provides the details on setbacks, privacy, solar access, design guidelines, etc.

To put this in context, here are a few scenarios in which these controls shape what is possible:

1. An R2 zoned property in Sydney typically carries a maximum building height of 8.5 metres and a floor space ratio that limits total floor area to a set proportion of the site.
2. A rear extension may need to sit a minimum distance from the boundary to protect a neighbour's solar access.
3. An addition in a heritage conservation area may need to be set back from the street to remain invisible from the footpath.

These controls do not simply restrict what is possible. They also reveal where the opportunities are. A good architect reads planning controls not as a checklist of limitations, but as a starting point for understanding what a site will genuinely support.

Site-specific overlays add further considerations, such as:

• Heritage conservation area controls: materials, building form and street-facing alterations
• Bushfire or flood overlays: construction requirements and building placement
• Solar access and privacy rules: setbacks and the massing of a building

The NSW Planning Portal is a reliable starting point. An architect familiar with your local council can then translate those controls into what they mean for your specific site and ambitions.

The Difference Between a DA and a CDC

Most residential projects in NSW require formal approval before work begins. The two most common pathways are a Development Application (DA) and a Complying Development Certificate (CDC).

A DA is assessed by your local council and involves public notification, neighbour review and evaluation against local planning controls. It is the more flexible pathway, suited to complex, non-standard or heritage projects. The trade-off is time: DAs typically take three to six months once submitted. A DA addresses planning permission only, so a Construction Certificate (CC) is also required before building work can begin. A CC is assessed by a private certifier and confirms compliance with the Building Code of Australia.

A CDC is assessed privately by an accredited certifier against a fixed set of state standards and incorporates the CC, meaning a single approval covers both planning and building compliance. If your project meets those standards precisely, approval takes weeks rather than months. There is less flexibility, but for straightforward projects it is often the more efficient route.

To illustrate: 

A single-storey rear extension on a standard R2 block in Randwick, with no heritage overlay and a design that meets all relevant state standards, would likely qualify for a CDC. The same extension on a heritage-listed property in Paddington, or one that pushes against the site's floor space ratio, would likely require a DA through the local council.

Designing for Your Site

How Site Conditions Shape What's Possible: Slope, Orientation and Size

Every site has its own character, and that character shapes the design from the very beginning. Slope, orientation and size are not obstacles to work around. In the right hands, they become the starting point for something considered and particular to its place.

Slope: 

Slope influences how a building meets the ground and where natural light enters. A steeply sloping site might limit certain configurations, but it can also create opportunities for split-level living, elevated outlooks and spaces that open to the landscape in ways a flat block never could.

Orientation: 

Orientation determines how a home responds to the sun and breeze. A north-facing living area captures winter sun and can be shaded from summer heat with a well-placed eave. Poor orientation is harder to resolve, but thoughtful design can mitigate it through careful window placement, skylights, and cross-ventilation.

Size: 

A compact urban block demands efficiency and precision, with the relationship between inside and outside becoming especially important. Larger sites offer more freedom but raise questions about scale, privacy, and connection to the landscape.

Across Sydney and NSW, most sites come with at least one complicating condition. The ones that appear most constrained often produce the most thoughtfully designed homes.

Architect Fees and Construction Costs in Sydney

How Architects Charge and How Fees Are Structured

Architect fees are not one-size-fits-all. They reflect the scope, complexity and level of service a project requires, and are structured in a few different ways depending on what suits the project and the client.

The most common approach for residential work is a percentage of the total construction cost. Complex or heritage projects typically attract higher fees than straightforward new builds. For percentage-based engagements, fees are broken down by stage, covering:

• Concept design
• Development application
• Construction documentation
• Contract administration

A lump sum fee works well when the scope is clearly defined from the outset. An hourly rate tends to suit early-stage advice, feasibility assessments or smaller commissions where the brief is still forming.

Most architects offer an initial conversation at no cost. A full architectural service covers everything from the first sketch through to the completion of construction, with your architect acting as your representative at every stage.

What It Costs to Renovate, Extend or Build in Sydney

Construction costs in Sydney vary widely depending on the size, complexity and finish level of a project, as well as site conditions and current market rates, making it difficult to provide figures that are meaningful without understanding a project in detail.

The most reliable way to develop a realistic cost picture is through your architect's informed view based on comparable projects, an early estimate from a builder familiar with your architect's work, or a detailed cost plan from a registered Quantity Surveyor on larger or more complex projects. Each has its merits depending on the stage and scale of your project.

Construction costs cover building work only. Architecture, engineering, planning and other consultant fees are additional, as are council and statutory costs.

Clear documentation and a properly tendered builder contract give you the best chance of staying within budget. A good architect will help you understand where your project sits within these bands from the earliest stages of design.

Renovating or Extending Your Home in Sydney

Making the Right Decision

Is It Better to Renovate an Existing Home or Build New?

For many Sydney homeowners, a renovation or extension is the preferred path rather than a knockdown rebuild. The existing structure, the character of the home, the garden that has matured over decades, and the street presence built up over time. These are worth preserving when the bones of a house are sound.

That said, the right answer depends on the condition of your home and what you are trying to achieve. A house with serious structural problems, a layout that cannot be resolved without near-total demolition, or one that has been so altered over the years that little of value remains, may be a genuine candidate for rebuilding.

A few questions worth considering early:

• Is the existing structure sound, or are there significant issues with the bones of the building?
• Does the current layout have the potential to become what you need, or is it fundamentally at odds with how you want to live?
• Are there heritage controls or planning restrictions that limit what can be changed or removed?
• How long do you intend to stay, and does the investment align with that timeframe?

Renovation and extension, done well, can transform a home entirely while retaining what gives it its character. For homes with genuine architectural merit, it is almost always the more considered path. Additionally, retaining as much of the original fabric as possible will nearly always be the most sustainable approach.

What Changes Add the Most Value to a Sydney Home?

This question is worth approaching from two angles: financial return and quality of life. The most meaningful projects are those where the two align.

The changes that tend to deliver the strongest returns are those that address what the home fundamentally lacks. That might be light, space, a connection to the garden, or a layout that no longer suits the way a family lives.

The interventions that add the most value, broadly:

• Opening the rear of the home: extending into the garden to create generous kitchen and living spaces that connect inside to outside, is one of the most consistently rewarding changes in a home.
• Improving natural light: skylights, larger openings and the removal of dark, compartmentalised rooms transform how a home feels to live in every day.
• A well-designed primary bedroom suite: considered storage and a quality bathroom are consistently valued by buyers and occupants alike.
• Kitchens and bathrooms with quality finishes: these are the rooms that date most visibly and reward thoughtful investment
• Flexible spaces: a home office, a guest room that doubles as a study, or a living area that adapts to different uses add genuine utility.

The quality of the design matters as much as the scope of work. A modest extension designed with care and precision will outperform a larger one that ignores how light moves through the spaces or how the family actually lives.

Heritage Home Renovations and Extensions

What Does It Mean If a Home Is Heritage-Listed or In a Conservation Area?

Heritage listing or inclusion as a contributory item in a conservation area means your home is recognised as having historical, architectural or cultural significance. That recognition comes with a set of controls that govern what changes are permissible and how they are carried out.

Heritage listing applies to individual properties identified as significant in their own right. A conservation area is broader, covering a streetscape or neighbourhood where the collective character is considered worth protecting. Your property does not need to be individually listed to be affected; if it sits within a conservation area, some of the same controls will likely apply.

In practical terms, any work that alters the appearance, fabric or character of the building will be assessed against heritage guidelines. Some changes require council approval that a non-heritage property would not need. Others may be restricted or refused entirely.

What this does not mean is that nothing is possible. Heritage controls are not a prohibition on change. They are a framework for change that is considered, respectful and well-reasoned. Thoughtfully designed alterations and additions to heritage homes are approved in Sydney and throughout NSW every day.

The NSW Heritage Office provides guidance on heritage controls and obligations across the state.

What You Can Change and What Is Likely to Be Approved

When renovating a heritage home or one in a conservation area, what you can change depends on your listing, your council and the nature of the work. But some principles hold broadly across Sydney and NSW.

Street-facing elements are typically the most tightly controlled. Original facades, rooflines, windows, doors and materials are generally expected to be retained and restored rather than altered. In suburbs like Paddington, Woollahra and Annandale, where rows of Victorian and Federation terraces define the character of entire streets, councils are particularly attentive to anything visible from the public domain.

The rear of a property usually offers more scope. Extensions, new openings, skylights and internal reconfigurations are regularly approved in heritage homes, provided they are sensitively designed and do not compromise the integrity of the original building.

Internally, there is often considerable freedom. Changes to layout, finishes and services that do not affect the exterior or significant interior fabric are generally permissible without the same level of scrutiny.

Heritage terraces in the Inner West and Eastern Suburbs present particular challenges of their own. Long and narrow, with limited natural light, steep staircases and compartmentalised rooms, they reward the kind of careful, site-specific thinking that unlocks space and light without erasing what gives the home its character.

The Renovation and Extension Process in Sydney

How Long Does a Residential Renovation or Extension Take?

The honest answer is that it depends on the scale and complexity of the project. But most homeowners underestimate the time involved, particularly in the early stages before construction begins.

For a meaningful renovation or extension, a realistic total timeline from first conversation to completion looks something like this:

1. Design and documentation: two to four months
2. Approval via CDC: two to four weeks
3. Approval via DA: three to six months, longer for heritage properties or complex sites
4. Builder selection and contract: one to two months
5. Construction: Highly dependent on the nature of the scope

A single-storey extension with straightforward approval might be completed within 8 to 12 months. A second-storey addition, a complex renovation, or any project requiring a DA in a heritage area should be planned over 12 to 18 months or more.

It is also worth accounting for conditions particular to Sydney. Older homes in the Inner West or on the North Shore often reveal unexpected issues once work begins, from asbestos to structural problems that require careful resolution. Tight urban sites slow demolition and deliveries. Any project that spans December and January will lose two to three weeks to the summer shutdown.

Building a New Home in Sydney and NSW

Process and Timelines

The Process From First Conversation to Completed Home

Designing and building a new home is a long and considered process. The stages broadly unfold as follows:

1. Initial conversation and briefing: the first meetings are about understanding your site, your life and what you want the home to do. This is where the brief takes shape, and the architect begins to understand the constraints and opportunities specific to your land.
2. Concept design: the architect develops initial design ideas that respond to the brief, the site and the planning controls. This is where the character and spatial organisation of the home begins to emerge.
3. Design development: the preferred concept is refined and resolved in greater detail. Structural, material and technical decisions begin to be made, and the design is tested against your budget.
4. Development application or CDC: documentation is prepared and submitted for planning approval. For a DA, this typically takes three to six months. A CDC, where applicable, is considerably faster.
5. Construction documentation: once approved, detailed drawings and specifications are prepared for tender and construction.
6. Tender and builder selection: the project is put out to a select group of builders for pricing. Your architect helps you assess the tenders and select the right builder for the project.
7. Construction and administration: building begins. Your architect administers the contract, makes regular site visits and acts as your representative throughout
8. Completion: the home is handed over, defects are identified and addressed, and the project reaches practical completion

How Long Does it Take to Design and Build a New Home in Sydney?

From the first conversation to moving in, most custom-designed architect homes in Sydney take between 18 months and 2.5 years.

Design, documentation, and approvals typically take 6 to 12 months before construction begins. A DA in a straightforward residential zone might be determined in three to four months. A heritage site, a complex council area or a project requiring additional studies can extend that considerably.

Construction generally takes twelve to eighteen months, depending on scale and complexity. Site conditions specific to Sydney add their own considerations: sloping blocks require more complex foundations, tight urban sites slow deliveries and access, and the summer shutdown period is a near-universal feature of the Sydney building calendar.

The factors that most commonly influence the timeline include:

• Site complexity: slope, access, soil conditions and demolition requirements
• Approval pathway: CDC or DA, and whether heritage or environmental overlays apply
• Design complexity: homes with custom detailing and specialist trades take longer to build
• Builder and trade availability: quality builders in Sydney are in demand and worth waiting for

Rushing the early stages rarely saves time overall. A well-considered, thoroughly documented design gives your builder the clarity to work efficiently and gives you the best chance of a smooth build.

Working With Sam Crawford Architects

Every project begins with a conversation. At Sam Crawford Architects, we listen first, then work to understand what your site makes possible and what your life requires from a home.

Whether you are renovating a terrace in the Inner West, extending a home on the Northern Beaches, or building something new on a site that deserves a considered response, we bring the same rigour, care and clarity to every stage of the process.

If you're considering renovating, extending or building a home in Sydney, an early conversation can help clarify what's possible for your site and your budget. Contact us. We welcome the opportunity to work with you to create a home that is thoughtfully designed for the way you live.