Architect vs Building Designer: What’s the Best Way to Start Your Extension?

Planning a home extension project? Whether you're aiming to add space, improve layout, or boost property value, one of the biggest early decisions is who to hire first. Should you engage an architect to draw up your plans, or start with a design and build company that can manage everything from concept to construction?

In this guide, we’ll compare both approaches, outlining the pros, cons, and key differences to help you choose the best path for your renovation. You’ll also learn how the design and construct model used by Supa Group helps homeowners achieve clarity on budget, design, and feasibility early in the process.

What's the difference: Architects and building designers

When planning a home extension, it’s important to understand the difference between architects, builders, and design and build teams. Each plays a distinct role in the design and construction process—yet their responsibilities, cost structures, and project involvement can vary significantly. Choosing the right model can impact everything from your timeline and budget to how closely your final build aligns with your original vision.

Understanding the relationship between a builder and architect can help clarify who does what, and when each is needed during your extension journey.

What does an architect do in a home extension?

A house extension architect focuses on the design phase of your renovation or addition. They turn your ideas into detailed plans—shaping your home's layout, structure, and aesthetics. Architects conduct site analysis, consider your lifestyle goals, and create concept drawings and working plans.

They also handle compliance by navigating building codes, zoning rules, and permit approvals. However, most architects are not involved in the actual build, so you’ll still need to engage a builder separately to quote and construct the project.

What is the builder’s role in an extension project?

A builder is responsible for bringing your plans to life. Once the architectural drawings are complete, they manage the practical side of the project, coordinating trades, sourcing materials, and overseeing the build onsite.

Builders don’t usually contribute to the design phase but work to interpret and execute the supplied plans. If the design doesn’t match real-world site conditions or budget expectations, this can lead to delays, rework, or costly plan changes.

What does a design and build company offer?

A design-and-construct team like Supa Group combines design and construction services under one roof. These companies create your concept plans, estimate costs based on real-time construction data, and then carry out the build—all within the same team.

This integrated model ensures that your design is feasible from day one, reducing the risk of redesigns and improving budget control. With clearer communication and a single point of contact, design and build services often deliver faster, more coordinated outcomes for home extensions.

[feature_link]Read more: How to find the right design to suit your home extension.[/feature_link]

Key differences between design and build vs architect-first projects

When planning a home extension, the structure of your team matters. Understanding how traditional architect-led models compare with integrated building design services can help you make smarter decisions from the outset.

‍

[process_video]Learn more about our process[/process_video]

Why starting with a design and build team can save time and money

Choosing a design and build team means you’ll work with a single company from initial concept to construction. Instead of managing separate contracts for an architect and a builder, you get one integrated team that handles design documentation and project delivery.

This approach simplifies communication, reduces admin, and allows budget and feasibility to shape your design. Below, we summarise the key advantages of starting your project with a design and construct builder.

Early budget clarity

One of the main risks with an architect-first project is that detailed drawings are completed before any real construction costs are confirmed. This can result in unexpected budget blowouts later in the process.

Working with a design-and-build company means your budget helps shape the design, not vice versa.

• Concept design and quote delivered within 4 weeks.
• Real-time cost feedback as design progresses.
• Avoids the need for costly redraws due to budget misalignment.

Focus on feasibility

When homeowners work with an architect, the design process often begins with visual and structural aspirations, long before costs or practical limitations are assessed. While the outcome might be an impressive set of plans, it’s not uncommon for clients to discover late that the design exceeds their budget or isn’t feasible to build on their site.

By contrast, design and construct teams assess buildability and budget parallel to the design process. This means you’ll get early feedback on whether your vision can realistically be delivered—and where adjustments may be needed.

• Architects typically focus on design outcomes first, then bring in costing later.
• Design and build teams offer construction-led feedback from day one.
• Potential issues like access, council overlays or structural limitations are addressed before plans are locked in.

This proactive approach reduces the need for costly redraws, saves time during approvals, and keeps your expectations grounded in what's achievable.

Simplified communication and collaboration

Communication can quickly become fragmented when working with separate architect and builder teams. You may find yourself relaying information between professionals, clarifying misinterpretations, or trying to align competing priorities. This siloed approach often leads to delays, oversights, and homeowner frustration.

With a design and construct team, communication is centralised. One company manages the process from the initial concept design to the final build, ensuring your goals are consistently understood and acted upon across all stages.

• Architect-first projects often require the client to coordinate between teams.
• Design and build removes the need for a middleperson.
• Fewer handovers mean fewer misunderstandings, faster decisions, and better alignment.

This integrated structure fosters a collaborative environment where design intent, budget constraints and construction realities stay in sync.

Want to understand how design and construct contracts work? This LegalVision guide breaks down the key features of D&C agreements and what to expect when engaging a builder under this model.

Streamlined decision-making

In architect-led projects, major design decisions are made early, often without input from the builder. Once construction begins, the builder may raise issues with materials, sequencing, or site logistics, which can lead to changes that require costly redraws and time-consuming revisions. Each adjustment might involve returning to the architect and being charged for it.

Design and build companies approach decision-making differently. Builders, designers, and engineers work together from the start, offering input on cost, feasibility, and buildability at every step.

• Architect-led workflows can involve multiple rounds of revisions, often billed separately.
• Design and construct teams make coordinated decisions during early design, reducing back-and-forth.
• Preferred materials and efficient build methods are factored into the design before finalising documentation.

The result? A smoother process, clearer expectations, and fewer costly changes once construction is underway.

Industry experience

Architects often focus on the design vision and compliance, but may have limited exposure to current construction costs, material lead times, or buildability issues. This can result in beautifully drawn plans that are difficult or expensive to bring to life.

Design and build teams, on the other hand, are grounded in real-world construction. They collaborate daily with trades and suppliers, giving them a sharper sense of what works, what’s available, and how to build efficiently.

• Better understanding of current labour and material costs.
• Build methods are factored into the design from the start.
• Practical, experience-led advice during the design phase.

Design-build options

A key advantage of design-construct teams is that the design phase is tailored not only to your vision but also to the builder's construction approach. Unlike architect-led projects, where the builder comes in after the design is finalised, this model allows you to explore your options with buildability and cost already in mind.

At Supa Group, for example, the process begins with a concept design phase that includes 3D walkthroughs. This lets you visualise your new home extension before making final decisions.

• Supa Group delivers concept design and a fixed-price quote within ~4 weeks.
• Designs include input from builders, engineers, and draftspersons working together.
• 3D visualisation lets you make confident changes before committing to build.
• Designs include input from builders, engineers, and draftspersons (also known as draftsmen or draftswomen) working together to deliver a buildable, budget-aligned concept.

Not sure what a draftsperson does? They create detailed technical drawings based on design plans, ensuring the project is accurately documented and ready for approval and construction.

This collaborative approach helps avoid the all-too-common disconnect between the design on paper and what’s actually practical to construct, saving time, cost, and disappointment later.

Choosing the right path for your home extension

Architects and builders both play valuable roles in home design and construction. However, engaging them separately can introduce complexity, time delays, and budget risks, especially for extensions where buildability, budget, and approvals must be considered together.

A design and build approach offers a more practical alternative for many Australian homeowners. By working with one integrated team like Supa Group, you can align design intent with budget realities, reduce costly rework, and streamline the entire process from concept to completion.

If you’re planning a home extension and want clarity on your options, book a consultation with Supa Group to explore how design and build could work for your project.

[service_links]Get an award winning extension builder on your team[/service_links]