Can I Build An Extension On My House? | Houseace
Please Wait...

Can I Build An Extension On My House?


If you love your home but need a little extra space, it can be a great idea to build an extension – giving you the extra room you need whilst improving the property’s valuation and avoiding the hassle of moving. However, adding an extension to your property is no mean feat and needs plenty of consideration and planning.


Here, we’ve broken down the main factors to consider, as well as determining whether it’s even permissible and how to go about getting your plans approved.

Why extend?

Understandably, if you are painfully short on space, you need to either extend or move and if you really love where you live you may not want to move. Moving is, in itself, a mammoth task, and consequently, extending your current property may seem like a better fit for you and/or your family. A growing family can often find themselves in this predicament as children get older and need more space or their own bedrooms, for example.


Many renovations and extensions come about because people living in older properties are tired of all sharing only one bathroom.

In addition to these common reasons, others could include:

  • Renovating your home for a more open-plan design
  • Reconfiguring your home’s floor plan to maximise usable space
  • Increasing storage space 
  • Bringing in more natural light
  • Reconfiguring the general layout to move living spaces around

Factors that will affect the cost of a house extension

Not surprisingly, extensions can be costly and so it may be worth assessing whether you’ve fully considered all other options. For example, converting a garage into added living space is certainly a money saver as there is an existing structure to work with.


Another factor to consider is what you are planning to use the new space for. The cost per m2 to add an extension depends largely upon how the space will be used. For example, bathrooms are the most expensive to add, closely followed by kitchens. This is because both bathrooms and kitchens require additional plumbing and electrical work, as well as all the added fixtures and fittings required to turn a space into a workable kitchen or bathroom. 


Here is a list of the main factors that will influence the cost of your home extension:

  • The size of your planned extension
  • How many floors you will be adding
  • The quality and type of materials you plan to use
  • Any appliances and fittings you choose
  • The costs of engaging professionals such as land surveyors and engineers

In addition to these, there are other practical considerations, such as:

  • Accessibility to the site – parking and heavy vehicle access
  • The topography of the site – is the land flat or on a steep hill 
  • The extent of any demolition required
  • The extent of any excavation required
  • Any need for professional hazardous material removal (i.e. asbestos)

How much does a house extension in Australia cost?

Our estimation team reported the extension costs for 2019-2020 which is based on our pricing algorithm and past projects, this estimated an extension typically costs between $1,900 and $3,800 per m2.

This ballpark figure is based on the assumption that the site has good access and that the existing building being added to is in good structural condition. The price range is reflective of the differences in cost depending upon the scale of the project and the use of the space, as well as the materials used and the builder that is chosen. When it comes to materials, for example, a brick veneer extension is more costly than a timber-framed one.

If you are planning on adding a wet area to your extension, then the following respective ranges of costs should be added to the above building cost estimates:

  • Kitchen: $17,000 – $40,000
  • Bathroom or en-suite: $14,000 – $28,000
  • Laundry: $6,000 – $15,000

Plus, if you’re planning on adding a second floor, including stairs and any other structural work required to the existing building/roof, then the cost will go up considerably, potentially as much as double the costs outlined above.

However, that larger extensions can result in lower costs per m2 for a more economical build.

Other budgetary factors include professional fees for experts such as structural engineers, soil reports or land surveyors. 

Lastly, it is prudent to include a contingency buffer in case you run into any unforeseen expenses. An additional 10-20% of your budget is advised.

How much value can an extension add to a property?

This is not an easy question to answer with accuracy, as it depends upon a number of factors. 

When planning an extension, it certainly pays to consider the market and what it is that buyers in your area would value the most. For example, adding a bedroom to your home in an area that most appreciates this feature could see you realising a significant return on your investment – potentially as much as $150,000.

Comparing your property with others on the market in your area is a handy exercise in determining a ballpark idea of how improved your property and its value may become as a result of your extension.

What permits and approvals are needed for extensions?

Property owners can make superficial renovations to their heart’s content, but any structural renovations, including extensions, require permissions from your local council.

The costs of these applications and permits differ between councils, so it’s important to research them in your local area to include them accurately in your budgeting.

They may include:

  • Development applications
  • Demolition permits
  • Building permits
  • Town planning application and approval

Usually, architects and builders take care of these on your behalf, but it’s best that you understand them for yourself, including the costs involved. 

When it comes to achieving approvals, the primary factors that influence council’s decisions are:

  • Significant alteration of a property’s appearance
  • Impositions upon neighbouring privacies
  • Alterations proposed upon a heritage-listed building

In some instances, building alterations can be conducted via a simpler approval application process called a ‘complying development’, which is issued within 10 days for a speedier process.

If your project involves internal work only, it is unlikely that you will require any planning approval, but to be sure, it’s worth checking this with your local council office before commencing your alterations.

What professionals are required for extensions?

Your first move should be to engage the expertise of a building designer or architect. You will also need to find a reputable builder – one who you feel confident understands your vision and has a good reputation and local track record for quality and reliable work. The builder will then either use their own staff, or hire subcontractors as needed, so you won’t have to worry about engaging with electricians and plumbers, etc. yourself. It is imperative that you have a signed contract in place that you have had reviewed by an expert, preferably a lawyer. Don’t leave anything to assumption, and read the small print.

It sounds like a lot of work, but we can take care of the whole process for you at Houseace, creating plans for the best design to suit your preferences and lifestyle. Our expert project managers will also handle the whole project, to make sure everything runs smoothly. 

Extensions can certainly be a big task to see through, but the rewards and property improvements can be significant. Get a free online quote for your house extension, or give us a call on 1300 304 367 to find out more about the services we offer and how we can help.


Read More: A Guide To Home Horizontal And Vertical Extensions

The easiest way to quote, plan & manage your renovation

You're almost done. Are you sure you want to exit?

or contact us to help