Understanding the Cost of an Old Home Extension in Australia

Are you planning to extend your old home but are worried about the cost? 


Many homeowners find it challenging to determine the actual cost of an old home extension. Even with a clear budget of $250K, you might find the quote from the builder exceeding the budget, such as around $300K. 


Now, you’re asking yourself, “What is the actual cost of a home extension?” “Does the builder’s quote make sense?”  


The Cost of an Old Home Extension in Australia


According to service.com.au, the cost of an old home extension can vary depending on different factors: the size of the extension, materials used, and complexity of the work. 


For example, on average, an 80m2 ground floor extension for an old house ranges between $164,500 to $310,000. It highlights the need to consider different variables when calculating the cost of a home extension.


4 Factors that Affect the Cost of Old Home Extension


  • Size of the extension
  • Type of extension
  • Materials used
  • Complexity of work


Size of the Extension


The size is a significant factor that determines your home extension cost. A larger extension will need more materials and labour. The shape of the extension also influences its price, with complex shapes costing more than simple ones.


Type of Extension


There are different types of extensions: ground-floor, first-floor, and second-floor extensions. Their cost varies, with ground-floor extensions being the most affordable and second-floor being the most expensive.


Materials Used


The type of materials used for the extension also affects the cost. For instance, if you’re using premium materials like hardwood, the price will be higher than the alternative, such as treated pine. It also goes the same with the quality of finishes like tiles, paint, and fixtures, which may also impact the cost.


Complexity of Work


The complexity of the work also influences the cost of an old home extension. Extensive demolition, excavation, or structural work can affect the project’s price, and fixing the access issues, such as narrow driveways or steep slopes, will also add to the price.


How to Maximise Your Budget for an Old Home Extension


Now that you understand the factors affecting the cost of an old home extension, here’s how you can maximise your budget.


Plan and Design Carefully


To avoid unexpected costs, plan the design of your desired extension and include the cost and your budget. Consider the size, type, and materials you want to use, and prepare for potential challenges that could impact the cost.


Compare Quotes


Always get multiple quotes from different builders. It allows you to identify any price discrepancies and make an informed decision.




If you have a limited budget, prioritise the most critical aspects of the extension, such as increasing living space or adding an extra bedroom, and postpone any non-essential elements.


Be Flexible


Being flexible with your design and materials can help you save money. For instance, you can opt for a more affordable alternative, like treated pine, instead of expensive hardwood.




The cost of an old home extension in Australia varies depending on various factors. With careful planning, designing, and prioritising, you can maximise your budget and achieve your desired outcome. Always get multiple quotes, compare them, and choose a builder that offers quality work at a fair price. 


With the right approach, an old home extension can add significant value to your property, providing more living space and increasing its overall appeal. 


Remember, the initial cost of an old home extension is just one aspect to consider. Consider the long-term benefits, such as increased property value and improved quality of life, that can outweigh the initial expense.


When embarking on an old home extension, work with a reputable builder with experience handling such projects. Choose the one that understands the local building regulations well and can provide you with a detailed and transparent breakdown of the costs involved. Ensure they are fully licensed and insured to protect you from unforeseen circumstances.


Request a quote on our website now!


Related post

Request a Quote

Please fill out all of the form fields so that we can better serve you. The more we learn about you, the more we are able to assist.