Establish what your home can accommodate
Start with your household’s needs, the existing building and the planning controls for your property. Develop the design with the right professionals, then compare proposals covering the same work. Resolve the approval pathway and construction arrangements before committing to a start date.
Brief
Set room priorities and identify what you want to retain downstairs.
Feasibility
Have the existing structure and proposed changes assessed.
Scope
Include design, approvals, site work, services and disruption.
Decisions
Agree responsibilities, specifications and change procedures in writing.
Start with feasibility
Write a short brief: who will use the extra space, which rooms you need, what works well downstairs and what you want to change. Bring any available survey, existing plans and reports to the first discussion, along with a realistic budget limit.
Ask the project team to identify the main constraints before detailed design: the existing building, stairs and circulation, site access, services, neighbouring properties and applicable planning controls.
Have structural changes assessed
Arrange a qualified structural engineer to assess the proposed work. Ask what needs inspecting or testing, which parts of the existing building can be retained and what further design or strengthening may be needed. Do not infer load capacity from wall material or building age alone.
The Australian Government’s Your Home renovation guidance explains professional assessment and the distinction between planning and building approval.
Develop the design and documentation
Compare an architect or building designer’s relevant experience and written scope. Clarify who coordinates the engineer, site information, energy assessment, applications and construction documents. Confirm the registration or licensing requirements for each role in your jurisdiction.
Ask the designer to show how stairs affect the ground floor, how the two levels connect, and how room layout, privacy, storage, daylight and comfort work together. Discuss accessibility and future household needs before settling the plan.
Agree deliverables and decision points: concept options, developed plans, specifications, approval documents and the information builders will price. Ask which changes are included in the fee and who can use the drawings.
Your Home’s design process describes the roles of designers and specialist consultants.
Confirm the approval pathway for your property
Planning permission and building approval address different questions. Ask your council and the relevant certifier or building surveyor what applies to your address, proposal and existing approvals. A streamlined planning pathway is conditional, rather than a national entitlement.
- New South Wales example
- The NSW Housing Code allows qualifying alterations and additions as complying development. Eligibility depends on the land and proposal meeting the relevant requirements; other proposals need a different pathway.
- Victoria example
- Consumer Affairs Victoria advises checking planning-permit requirements with council and building-permit requirements with a surveyor or the relevant authority. These are separate checks.
Have the designer confirm height, setbacks, privacy, overshadowing, heritage or hazard controls and the documents needed for assessment. Ask which current energy-performance requirements apply to the addition and any affected existing work.
Record who lodges applications, responds to questions, books required inspections and obtains completion documents. Check conditions and required approvals before work starts. For other jurisdictions, use the official starting points in our renovation approvals guide.
Compare quotes for the same work
Give each builder the same plans, specifications and known site information. Ask about comparable additions, supervision and references, and check the relevant licence or registration and insurance yourself.
- The existing home
- Identify what is retained, altered or removed, including any downstairs repairs or finishes affected by the work.
- Structure and access
- Include the engineer’s design, stairs, roof changes, scaffolding, deliveries and temporary protection. Name unresolved site allowances.
- Services and fit-out
- Compare the same plumbing, electrical work, heating or cooling, bathrooms, insulation, windows, joinery and finishes.
- Approvals and reports
- Record who arranges drawings, applications, engineering, assessments, inspections and completion documents, and which fees are included.
- Allowances and exclusions
- Separate fixed work, provisional sums, selections and excluded work. Ask how each allowance is adjusted and how variations are agreed.
- Delivery and handover
- Agree supervision, communication, timing, site clean-up, completion criteria and the process for reporting and addressing defects.
Resolve the contract before paying
Agree the work, price basis, allowances, start and completion terms, payment stages, variations and defect process in writing. Check the local rules and get independent advice on terms you do not understand.
NSW’s building contract guidance explains licence checks, written terms and progress payments. Victoria’s deposit and payment guidance sets out its own requirements. A generic percentage schedule is not a substitute for the rules and contract applying to your project.
Considering owner-building?
Understand the responsibilities before choosing that role. NSW’s owner-builder guidance covers supervision, approvals, licensed trades, contracts and insurance. Check your own jurisdiction’s requirements and discuss the implications with suitable advisers rather than assuming a particular saving.
Agree how the work affects daily life
Ask the builder to assess whether the home can be occupied at each stage. Discuss separation from the work area, safe access, weather protection, dust and noise, essential services, children and pets. Agree when alternative accommodation is needed and how changes will be communicated.
Before signing, discuss construction cover with the builder and check your own home and contents policy with your insurer. Confirm responsibilities, exclusions and the effect of any unoccupied periods. NSW’s insurance guidance distinguishes contractor cover from your own policy and advises notifying your insurer before work begins.
Keep a record of agreed decisions and changes. Ask the appointed certifier or surveyor which inspections are required, when they occur and what must be provided at completion. Arrange a handover review and document any outstanding work.
Plan the complete budget and programme
Separate the building quote from professional fees, reports, application costs, work outside the builder’s scope and any temporary accommodation or storage. Identify allowances that remain uncertain and discuss how to fund changes without relying on an advertised package total.
Ask for stage estimates covering feasibility, design, approvals, procurement, construction and handover. Confirm what must happen before the construction period starts, which decisions you must make, and how delays or changes are handled under the contract.
There is no dependable nationwide construction period or guaranteed increase in property value. If resale value drives the project, seek an independent assessment for the proposed design and location. Our extension cost guide explains scope comparison and attributed examples.
Sources reviewed 16 October 2026. Confirm requirements again when developing your application and contract; the linked state examples do not establish rules for every jurisdiction.
