A rear extension or first floor addition in Sydney typically takes 12 to 22 months from first conversation to handover: 6 to 12 months of planning and approvals, then 6 to 10 months of construction.

One of the first questions homeowners ask when considering a renovation, a rear extension or first floor addition is: “How long will it take?”

It is an important question, particularly for families trying to plan around work, school, accommodation and everyday life.

But the answer is not as simple as giving you a construction start and completion date.

A significant amount of work is completed before a builder arrives on site. From initial discussions and architectural designs through to planning approvals, construction documentation and final pricing, the preparation phase is a major part of the renovation journey.

In fact, depending on the project, the planning and approval process generally takes from 6 to 12 months before construction even begins.

Understanding this timeline is important because it helps homeowners plan realistically, know what to expect and appreciate why each stage has a purpose.

The Renovation Journey: From First Conversation to Handover

Every home and project is different, but a typical rear extension or first floor addition follows a series of stages.

1. The Initial Planning Stage

Before engaging an architect or committing to detailed plans, it is worth having an initial conversation with an experienced local builder.

This is an opportunity to discuss what you want to achieve, the existing property, your intended investment and the practical considerations that may influence the project.

For example, a sloping block, difficult site access, an older existing structure or significant structural changes can all affect the complexity of a renovation.

Having these conversations early helps establish whether your expectations are realistic and gives you a better understanding of what lies ahead.

It also allows the builder to offer practical construction advice before the design becomes too advanced.

2. Design Development: Allow 2-6 Months

The design phase is where your ideas start becoming a detailed plan for your future home.

Working with your architect or designer, you will develop the layout, room sizes, structural elements and overall appearance of the proposed extension.

This stage involves more than deciding where walls and windows will go. It is about considering how your family uses the home, how the new spaces connect with the existing property and how the finished design will function over the long term.

Depending on the complexity of the project and how quickly decisions are made, this stage typically takes between two and six months.

At HDMB, we recognise that the design process needs to consider both what is possible architecturally and what is achievable from a construction perspective.

That is why we encourage early builder involvement and review the likely project cost as the design develops. An initial opinion of probable cost helps establish whether the concept is aligned with the intended investment before too much time is spent developing it.

3. Council and Planning Approvals: Allow 2-6 Months

Once the design documentation is ready, the project moves into the relevant approval process.

For Sydney homeowners, this will generally involve either a Development Application (DA) or a Complying Development Certificate (CDC), depending on the property and proposed works.

DA approval can take approximately two to six months, depending on the design, planning controls and individual council requirements.

A CDC is generally a quicker pathway where the proposed design already meets the relevant planning requirements.

It is important not to underestimate this stage. Approval timeframes are not entirely within the builder’s or homeowner’s control, so allowing sufficient time is essential when planning a potential construction start.

4. Design Development and Construction Documentation

Receiving planning approval is an important milestone, but there is still work to complete before construction can commence.

The architectural drawings need to be developed into the detailed documentation required for building. This will include engineering details, construction and finishing specifications and any additional information needed for detailed costing and issue of the Construction Certificate.

At HDMB, this is also when we undertake a second budget estimate check.

As the drawings become more detailed, we revisit the likely construction cost to make sure the project remains aligned with the homeowner’s expectations.

Once the necessary approvals and construction documentation are complete, we can prepare a detailed quotation, clearly outlining the scope of work, inclusions and exclusions.

This provides a much clearer basis for the building contract and the next stage of the journey.

5. Construction: What Happens Once Work Begins?

Only after the planning, approval and documentation stages are complete is the project ready to move into construction.

Typical construction timeframes for Sydney projects are:

• Rear extensions: approximately 6-9 months.
• First floor additions: approximately 8-10 months.
• Extensive renovations involving both: may exceed 10 months.

During this period, the work progresses through demolition, structural construction, framing, services, internal finishes and final detailing.

The exact sequence and duration will depend on the design, site conditions, weather and material availability.

For most extensions and first floor additions, homeowners will need temporary alternative accommodation. Significant structural work can make remaining in the home impractical, so this is an important part of planning the overall timeline.

Why HDMB’s Process Gives Homeowners a Clearer Picture

At HDMB, we believe that a well-managed project starts with a clear understanding of the journey ahead.

Our process is structured to guide clients through each stage, rather than treating construction as the only part of the project that matters.

There are several important milestones along the way, including:

• An initial discussion to understand your project, requirements and expectations.
• A site inspection to assess the existing property and potential challenges.
• An initial budget estimate during concept design.
• A second budget check once the architectural drawings have been developed.
• Planning approvals and completion of construction documentation.
• A detailed quotation and building contract before construction.
• A construction schedule and ongoing project management throughout the build.

Each stage builds on the one before it. This gives homeowners a better understanding of what decisions are required and when they need to be made.

It also means that important considerations are addressed progressively, rather than leaving everything until construction is about to begin.

Planning Your Life Around Your Renovation

The renovation timeline is not just about the builder’s programme. It is also about your family’s life.

If you are planning to renovate in the next 12 months, for example, it is worth considering when you would ideally like construction to commence and working backwards from there.

Think about school terms, work commitments, holidays, accommodation arrangements and any other factors that may influence your timing.

It is also important to understand that the design and approval stages can take longer than expected. Having a realistic timeframe from the beginning gives you greater flexibility and avoids unnecessary pressure to rush important decisions.

Start With a Clear Plan

A rear extension or first floor addition is a significant undertaking, and the time spent planning it is just as important as the time spent building it.

Understanding the different stages, allowing realistic timeframes and working with a builder who has a clearly defined process can make the experience far more straightforward.

At HDMB, we want our clients to understand not only what we are building, but how we will get there. By guiding homeowners through the planning, budgeting, approval and construction stages, we help create a clearer path from the first conversation to the day they receive their keys.

Thinking about extending your Sydney home?

The best time to start planning is often earlier than you think. Contact HDMB for an initial conversation about your ideas and a realistic timeline required to bring your project to life.

Visit hdmb.com.au or call Jay on 0483 947 074.

Frequently Asked Questions About Home Extension Timelines

How long does a rear extension take to build in Sydney?

A rear extension typically takes approximately 6 to 9 months to build once work begins on site. First floor additions generally take 8 to 10 months, and extensive renovations involving both may exceed 10 months. The planning and approval process before construction usually adds a further 6 to 12 months.

How long does council approval take for a home extension?

A Development Application (DA) can take approximately two to six months, depending on the design, planning controls and individual council requirements. A Complying Development Certificate (CDC) is generally a quicker pathway where the proposed design already meets the relevant planning requirements. Approval timeframes are not entirely within the builder’s or homeowner’s control.

What is the difference between a DA and a CDC?

Sydney homeowners will generally need either a Development Application (DA) or a Complying Development Certificate (CDC), depending on the property and proposed works. A CDC is usually quicker when the design already meets the relevant planning requirements, while a DA goes through the council assessment process.

Do I need to move out during a home extension?

For most extensions and first floor additions, homeowners will need temporary alternative accommodation. Significant structural work can make remaining in the home impractical, so it is important to build accommodation into your plans and your overall timeline from the start.

When should I speak to a builder about an extension?

Before engaging an architect or committing to detailed plans. An early conversation with an experienced local builder helps establish whether your expectations are realistic, and early involvement lets the builder review the likely cost as the design develops. You can see how HDMB’s process works from the first conversation through to handover.