How much does an extension cost?

Wondering about house extension costs? If you’re planning on making major changes to your home and adding more space, you’re probably wanting to know what the cost of an extension might be these days.

Generally, you can expect to pay $160,000 to $320,000 for an 80 square metre house extension on the ground floor. This equates to approximately $2,000 to $4,000 per m2 for the cost of extension. Keep in mind, second-storey extension costs are about 50 per cent higher than those constructed on the ground floor.

When you build an extension, the total outlay for house extension costs will depend largely on the type of construction you opt for and the quality of the materials and inclusions.

In this house extension cost guide, we explore:

• What affects the cost of building an extension
• How much do house extensions cost?
• The cost of extension by room type
• Other home extensions costs
• House extension ideas
• How to get extension building quotes, and more.

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What affects house extension costs?

How much do extensions cost and what affects the price? There are a range of different factors that can affect the cost of an extension. Foremost, the type of house extension will affect the price drastically.

House extension cost per m2 is usually higher for bathrooms and kitchens, while living areas and bedrooms are generally less expensive. This is due to the amount of plumbing and electrical work required, as well as fittings and fixtures, and tiling and waterproofing of wet areas.

A larger living space or an extra bedroom can be accommodated on a budget with a simple garage conversion.

Other factors that affect extension costs include:

• Size of your house
• Whether you are adding another storey
• Type of materials, fittings and appliances you choose
• Whether you engage additional professional support, such as an engineer, architect or land surveyor
• Extension building permits
• Ease of access to the site
• Whether your home is on a slope or a flat block
• If demolition or excavation work is needed
• Hazardous waste removal costs (i.e. asbestos).

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House extension cost per m2 Australia

How much does it cost to extend a house? House extension costs are often quoted in square metres or as a total project price. To build an extension, you can usually expect to pay anywhere between $1,900 and $4,000 per square metre, depending on your requirements.

While a ground floor extension could set you back between $1,900 and $4,000 per square metre, adding a second-storey usually falls within the range of $3,000 to $3,500 per m2.

The cost of building an extension for a second-storey is usually about 50% higher than a ground floor extension. However, it can work out cheaper in some cases, due to less land use or no excavation work being required. Knocking out walls or other repairs or renovations can also increase the cost of home extension.

Once you have your plans ready, you’ll be able to get more accurate quotes for the cost of extensions.

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House extension costs by room type

How much does house extension cost for various rooms? While a bathroom extension could cost you as much as $28,000 for a high-end finish, a laundry, living room or bedroom extension will be a much more affordable and quicker build.

Here is a room extension cost guide estimate:

• Bathroom/ensuite: $12,000 – $28,000
• Kitchen extension: $15,000 – $40,000
• Laundry: $6,000 – $15,000

If you’re adding a master bedroom and ensuite, extension cost will be less than with a full sized bathroom. An ensuite extension or budget bathroom can cost between $2,500 and $15,000. If you’re adding a new bathroom to an extension, it will likely cost more than ripping out and renovating an existing bathroom. You’ll have to cover plumbing costs for new pipes and sewerage, as well as electrical components such as wiring, outlets and lighting.

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Other home extension costs to consider

When planning a home extension, there are several costs to consider beyond the price of the actual construction. Here are a few additional items you may need to budget for:

• Permits and inspections
• Architect or designer fees
• Project management
• Demolition and site preparation
• Plumbing and electrical
• Materials and finishes (flooring, countertops, lighting and plumbing fixtures, etc)
• Heating and cooling
• Furnishings (new furniture, window treatments, appliances, and other items to fit the new space)
• Landscaping and hardscaping costs
• Financing.

It’s important to consider all of these costs when planning your budget, to ensure you have enough funds to complete the project. It’s also a good idea to add a contingency fund for unexpected costs that may arise during the construction process.

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House extension ideas

Many homeowners and renovators want to put a modern extension on an old house in Australia. This adds additional living space and can significantly increase the value of a property. Let’s explore a few popular house extension ideas.

Small house extensions ideas

Here are a few small house extension ideas to consider:

• Adding a sunroom to the back your home
• Building a single-story extension on the side of the house
• A simple garage conversion to create more livable space
• A small second-story addition above an existing room, such as a bedroom or bathroom
• Adding a small detached structure to the backyard, such as a home office or studio
• Building a small porch or deck on the front or back of the house
• Building a small mudroom or entryway at the side or back of the house
• An attached garage with a room above it
• An outdoor living space, such as a pergola or gazebo.
• A small bathroom or kitchen extension.

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Two storey extension ideas, Australia

There are several ways to create a two-storey extension that will provide more living space and create a better flow for your home. Here are some two storey extension ideas:

1. A larger kitchen and dining area on the ground floor, with a master bedroom and ensuite on the second floor.
2. An open-plan living and entertainment space on the ground floor, with additional bedrooms and bathrooms on the second floor.
3. Having a home office or study on the ground floor, with a guest suite or additional bedrooms on the second floor.
4. A family room or playroom on the ground floor, with a master suite on the second floor.
5. A separate living area for older children or teenagers on the second floor, with a home gym or hobby room on the ground floor.

It’s important to keep in mind that a second storey extensions will likely require a building permit from your local council. It may also be necessary to consult with structural engineers to ensure your home extension project can be built safely and securely.

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How much value does an extension add to your property?

A house extension can add value to your property. The exact amount added will depend on several factors, such as:

• Type of extension
• Quality of the work, and
• Your local real estate market.

A well-designed and executed extension that adds additional living space, such as a bedroom or bathroom, can significantly increase a property’s value by up to 20 per cent. On the other hand, a poorly designed or executed extension may not add much value, or could even decrease a property’s value. The cost of house extensions should not set you back any more than ten per cent of your property’s current worth.

It’s important to do market research in your area to see what similar houses are selling for and what is in demand. Also, consult with a real estate agent or an appraiser to get a more accurate estimate of the value added by a house extension.

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Getting home extension cost quotes

For the most accurate indication of extension building costs for your home, it’s important to get multiple quotes so you can compare prices and services before making a decision. Also, it’s always a good idea to check references and review previous work of the contractors before hiring.

When deciding between quotes, ensure you check for what is and isn’t included in the cost of extension. For instance, is excavation or demolition work included in the cost or will this be extra?

While many builders will include these types of expenses in their quotes, if you receive a cheaper quote it may mean that these additional items have not been accounted for and you might incur additional costs later. When choosing a builder, request an itemised quote that shows exactly what will be covered.

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* All costs and prices quoted were sourced at the time this cost guide was written and should only be used as an estimate.