How much does a house extension cost in Australia?

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ARTICLE Persephone Nicholas, Stephanie Matheson

Costs for ground-level house extension in Australia start from around $70,000. When house prices are high, as they are in many parts of Australia at the moment, adding a room or extending your living area on the ground floor can be a more affordable way to create space than moving. Here are some things to consider when planning your extension.

How can you plan for a ground-level extension?

Ground floor extensions are typically more affordable than converting the loft or excavating basement space. A same-level extension typically costs anywhere between $70,000+, depending on where you live, the project specifications, your choice of materials including cladding, labour and project management. Adding more windows and internal walls contribute to cost too.

Be aware that smaller renovations can work out slightly more expensive per square metre than larger renovations as many of the overheads such as getting a DA from council are a fixed cost. We advise getting a fixed price from your renovation consultant before the project starts to ensure your renovation comes in on a budget. If your budget is tight, focus on the things you need, rather than want, to start with. You can always upgrade finishes, fixtures and fittings in years to come.

Early estimates from your renovation consultant are usually a guide based on a series of assumptions. Even when you get the actual quote, plan in a contingency budget of at least 15% for unforeseen extras or problems. This will help you cover expenses, such as having to repair leaks or taking care of structural problems without jeopardising your project.

Your builders will work from architectural plans. Major building work typically requires a planning permit from your local council as well as a building permit from a registered building surveyor. You can organise these yourself or employ someone else, such as your renovation consultant, to do it on your behalf.

Once the council accepts the drawings for your project it can be difficult to make changes and this is one reason why Concept Drawings of a renovation are so useful. They may be more expensive than line drawings, but they show you exactly what your finished renovation will look like, which means it’s easier to identify any misunderstandings or problems earlier in the process.

Costs of a single storey house extension

From $70,000

To gain an understanding of what type of extension you can achieve within this price range, check out this office addition in Hughesdale.

The importance of passive design

Using passive design principles when planning your extension means your home will need less heating and cooling to keep it at a comfortable temperature all year round. Design for passive solar protects a house from summer sun and promotes the escape of heat, while letting the sun in during winter and helping ensure that heat is retained. These strategies, combined with effective shading, insulation and sealing (except in tropical regions) can help reduce your reliance on artificial heating and cooling systems. Visit the Australian Government website YourHome for more information.

How do you create an open-plan home?

Open-plan homes, particularly those with good indoor-outdoor flow, are popular all over Australia. So it’s hardly surprising that one of the most common alterations is the creation of one large kitchen/dining/living space. Opening up walls is usually a straightforward process, however load-bearing walls may need to be strengthened, which will incur additional costs. Any electrical or plumbing points within the wall would also have an impact on the overall cost. If you are looking to simply remove a non-load-bearing wall between two rooms, you may be able to get this taken out and tidied on the same day.

For further inspiration, check out this $188,000 open plan renovation in Adelaide. 

How can I create indoor-outdoor flow?

Perennially popular bi-fold doors provide virtually uninterrupted views of outdoor areas and have come a long way over recent years. Look for doors with a smooth sliding function made from timber that will complement your deck if you have one. A corner design opens up the space even more to give you that great outdoor feeling.

Sliding doors take up less space than bi-folds and can be a great option, particularly if you’re looking for a door to open on to a more compact area. While they don’t open up completely, they do allow for controlled ventilation, depending on how far they are open. The two standard types of sliding doors are top hung or bottom rolling systems. Top hung doors allow the bottom sill to be completely flush, but they often require increased lintel support and installation generally takes longer, which costs more. Bottom rolling systems suit larger, heavier glass panels.

For further indoor/outdoor flow inspiration, see how renovation specialist Stephen Cox created indoor/outdoor flow in his own home by creating a landscaped outdoor area for approximately $50,000.

Do I need to re-clad my home?

Often when you are extending your home you will be able to keep the original cladding on your house and simply add more of the same type to your addition. However, if you need to replace it, take a look at these exterior home renovations (ranging from $33,500 - $250,000) for pricing and options on the different materials now available, as the right kind of cladding will keep your home weathertight and looking good for years to come.

Weatherboard is the traditional choice and remains a popular option in Australia. These days it can be made from timber, aluminium or other metal, acrylic, vinyl (PVC) and fibre-cement. These new materials give you more scope when it comes to design, are usually simple to install and are often low-maintenance too.

Cost to renovate the exterior of your home

From $33,500 - $250,000+

How to save money on the interior finish when doing a house extension

Finishing your new room’s walls, ceiling and flooring is the final step of your renovation project. If your budget it tight, focus on a quality neutral finish. You can always add custom touches and upgrades later on. When it comes to flooring, wooden laminates or vinyl floors are an affordable and attractive choice.


This article explores options ideas and costs for a same level home extension. You may also want to read our dormer extension price guide, second storey addition or loft conversion price guide or basement conversion price guide.

Get in touch with Refresh to discuss your home renovation project

If you would like to discuss options and ideas for your kitchen renovation project, please use the enquiry form on this page to provide us with your contact details. We will get in touch with you at a time that suits you to discuss your project. If you would like to provide us with more information about your project, we have a more comprehensive enquiry form on our "Get in touch" page too.

*All information is believed to be true at time of publishing and is subject to change.

Note: prices are rough approximations only and are subject to change. 

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