How Much Does It Cost To Extend A House

Extending a house can be an exciting prospect for homeowners seeking more space, better functionality, or an updated design. However, it’s essential to understand the potential costs involved in this significant project before committing.

The cost of extending a house in Australia can vary significantly depending on several factors, such as the type of extension, the complexity of the design, the location of the property, and the builder’s experience.

In this article, we will explore the various factors that influence the cost of house extensions in Australia, the different types of extensions available, and what to consider when planning your project.

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Types Of House Extensions

There are several ways to extend a house, and each option comes with its associated costs. Common types of house extensions include:

Single-Storey Extensions

A single-storey extension involves adding more living space on the same level as your existing home. This type of extension is typically the most cost-effective option, as it requires less structural work compared to multi-storey options.

Cost Range:

On average, a single-storey extension in Australia can cost between $1,500 to $3,000 per square metre, depending on the materials used and the complexity of the design. This can be affected by the location of the property as well, with prices in major cities like Sydney, Melbourne, and Brisbane typically being higher than in rural areas.

Double-Storey Extensions

Double-storey extensions involve adding an additional level to the house, either to create more bedrooms, a new living area, or other space. This type of extension can be more expensive due to the added complexity, including the need for reinforcing the existing structure and ensuring the foundation can support the extra weight.

Cost Range:

Double-storey extensions generally cost between $2,000 to $4,500 per square metre. The additional cost comes from the need for a stronger foundation, additional staircases, and the increased time for construction.

Second-Storey Extensions

This involves adding an entirely new level on top of your existing home. It’s often seen as a good option for those with limited yard space but who want to avoid the cost and disruption of moving. Second-storey extensions are more complex than single-storey ones due to the challenges involved in reinforcing the existing structure.

Cost Range:

Adding a second-storey extension typically costs between $2,500 to $4,500 per square metre. The price will vary depending on how the existing home is constructed and the access available for the builders.

Garage Conversions

If you have a garage that isn’t being fully utilised, converting it into a living space can be an excellent option. Converting a garage into a bedroom, office, or living room can be relatively affordable, particularly if no significant structural work is needed.

Cost Range:

The cost of converting a garage into a room can range from $1,200 to $2,500 per square metre, depending on the amount of work required. This is typically a cheaper option compared to full-scale extensions, as the basic structure already exists.

Basement Extensions

For homes with enough space beneath them, extending into the basement can offer valuable additional space. This extension type involves significant excavation, reinforcing the foundation, and ensuring proper drainage and ventilation. The cost tends to be high due to the complexity and depth of the work.

Cost Range:

Basement extensions can be the most expensive, typically ranging from $3,000 to $6,000 per square metre, depending on the size and accessibility of the area.

Outdoor Extensions

Adding a deck, outdoor kitchen, or alfresco area can be an attractive and functional way to extend your home’s living space. Outdoor extensions often require less work than indoor ones, but they can still vary significantly in price depending on materials, design, and features.

Cost Range:

Outdoor extensions like decks or patios can cost between $1,500 to $3,500 per square metre, depending on whether you’re using premium materials like hardwood timber or composite decking.

Factors Affecting The Cost Of A House Extension

Several key factors contribute to the overall cost of extending a house. These include:

Location

The location of your home plays a crucial role in determining the cost of your extension. Urban areas like Sydney, Melbourne, and Brisbane tend to have higher construction costs due to increased demand for tradespeople, stricter regulations, and higher land prices. On the other hand, in rural or regional areas, labour costs may be lower, although travel costs for contractors can offset some of these savings.

Size Of The Extension

The size of the extension is one of the most significant factors in the overall cost. Larger extensions require more materials and labour, which will increase the cost. Additionally, the complexity of the design and any custom features will also add to the price.

Design And Materials

The more intricate the design, the higher the cost. Custom-designed extensions that require specific materials or a high level of craftsmanship can quickly become expensive. Using high-end materials such as marble, stone, or premium timber for flooring or finishes will also increase the cost of construction.

Structural Modifications

If the extension requires significant structural changes, such as reinforcing the foundation or adding load-bearing walls, the cost will increase. If you are adding a second storey or a basement, the cost of reinforcing the existing structure will need to be factored into the budget.

Council Regulations And Permits

In Australia, local councils have strict building regulations that must be followed during any extension project. Obtaining the necessary permits, completing required inspections, and meeting zoning laws can all add time and cost to your project. Building approval fees typically range from $1,000 to $5,000, depending on the nature and scale of the extension.

Labour Costs

The cost of labour will vary depending on the location and the skill level of the contractors hired. Hiring a reputable builder or specialist, tradesperson will generally ensure a high-quality outcome but may come at a premium. Labour costs in metropolitan areas are typically higher than in regional areas, which can significantly impact the overall project cost.

Construction Timeframe

The length of time required to complete the extension can also influence the overall cost. The more complex the extension, the longer it will take to complete, which can lead to higher labour costs. Additionally, any delays or complications during the project can increase costs.

Site Conditions

If your home is situated on a sloped or difficult-to-access site, this can increase the cost of construction. Excavation, drainage solutions, and other site-specific challenges will need to be considered, which can add to the overall cost of the extension.

Additional Costs To Consider

Architect Or Designer Fees

Depending on the complexity of the extension, you may need to hire an architect or designer to help plan the project. Architects typically charge between $100 and $300 per hour or may offer a fixed-price service for larger projects. Designers may be less expensive but still contribute significantly to the overall cost.

Interior Design And Fitout

After the structural work is completed, you’ll need to consider interior finishes such as flooring, cabinetry, lighting, and paintwork. These costs can vary widely depending on the materials chosen, but a budget of $10,000 to $50,000 or more is common for high-end finishes.

Landscaping

An extension to your home might affect the landscaping, particularly if outdoor areas are involved. If your extension changes the footprint of the house or alters the garden area, you may need to spend extra on landscaping services. This could range from a few thousand dollars for basic work to $10,000 or more for complex designs.

Temporary Accommodation

During the construction process, you may need to find alternative accommodation if your home is no longer livable due to the ongoing work. This can add significant costs, especially if the extension takes several months.

Budgeting For A House Extension

To help with budgeting, it’s important to account for both the estimated costs and the potential for unexpected expenses. A common rule of thumb is to set aside an additional 10–15% of the total project cost for contingencies. This will cover any unforeseen issues, such as structural problems or changes to the design during construction.

It’s also wise to get multiple quotes from builders and contractors to ensure you’re getting the best value for your money. Building a rapport with your contractor and discussing the project in detail can help prevent hidden costs and ensure that everyone is on the same page.

Conclusion

The cost of extending a house in Australia depends on many factors, including the size and type of extension, location, materials, and complexity of the design. Single-storey extensions tend to be the most affordable, while double-storey, basement, or custom-designed extensions can be considerably more expensive.

When planning a house extension, it’s essential to factor in costs like permits, labour, and materials, as well as unexpected expenses.

While the cost of house extensions can be significant, the benefits—such as increased space, improved functionality, and enhanced property value—can make it a worthwhile investment in the long run. By doing thorough research, obtaining multiple quotes, and budgeting carefully, you can ensure that your house extension project stays within your financial means while delivering the results you desire.

Frequently Ask Question

Can I Do A Diy Extension To Save Money?

While it is possible to do some parts of an extension yourself, such as painting or landscaping, most significant construction work requires professional skills. Hiring a licensed builder and obtaining necessary permits is crucial to ensure the work complies with building codes and regulations. DIY extensions may result in safety hazards, insurance issues, or costly mistakes if not done correctly.

What Is The Roi On A House Extension?

The return on investment (ROI) for a house extension can vary depending on the type of extension, location, and market conditions. On average, homeowners can expect to recoup 50% to 70% of the cost of an extension when selling their property. Extensions that improve livability and add extra bedrooms or bathrooms tend to have higher ROI.

What Permits And Approvals Are Needed For A House Extension?

Permits and approvals required for a house extension depend on the scope of the project and local regulations. Typically, you’ll need a Development Application (DA) or a Complying Development Certificate (CDC). You may also need building permits for structural work, electrical, plumbing, and mechanical work.

Always consult with your local council or a building professional to ensure all necessary permits are obtained before commencing the extension.