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How Much Do House Extensions Cost?

Last Updated Oct 24, 2017 · Written by Rob Schneider


When you buy a home, you may not take a growing family into consideration. One day you face a dilemma. Should we move or add on a house extension? Moving can be expensive and time-consuming. Adding a house extension can add value to your home and allow you to stay in your current location, but how much is it going to cost?

  1. Why Consider a House Extension? 
  2. How Much Does a Home Extension Cost?
  3. Other House Extension Costs to Consider
  4. Consider All the House Extension Costs

Why consider a house extension?

Why consider a house extension when you could sell your house and move to a larger home? Here are four good reasons to consider adding a house extension:

  • If you like the area you're living in, you don't have to move
  • Make the changes you want to make and not settle for something that's just okay
  • A home extension may be more affordable than moving to a larger home
  • You may be attached to your current home and not want to leave

Remember that moving involves expenses and a great deal of effort. First, you have to put your home on the market and look for a suitable new home. If your house is smaller than you would like, a larger home is going to cost more. Think about moving costs, bank charges and other costs and a home extension may be less expensive than moving.

Cost of house extensions 

How much does a home extension cost?

You won't know the exact cost of a home extension until you've made plans and know how large the extension is going to be and what will be included in the extension. As a general rule, an 80 square metre ground floor extension costs between $164,500 and $310,000. That works out to between $2056m2 and $3875m2. The difference is in the type of construction and the quality of the inclusions.

If you're adding a second storey, the cost will be about 50 percent more than a ground floor extension. The reason for this is because a second storey doesn't require foundation work and other major expenses. If you want to add a second storey, the square metre cost will be between $3084 and $5812. If you need a second storey, it will be cheaper than making a larger ground floor extension and less land will be needed for the extension.

How much does a home extension cost?

These are the basic costs for a home extension, but depending on what needs to be done, a home extension can be more expensive. For example, you may need to have excavation work done. That will add to the cost. Since a home extension includes knocking out a wall, that may be an extra expense and the home may also need some minor renovations.

 

Other house extension costs to consider

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The basic cost of a house extension should include all the basics including roofing, cladding, interior cladding, insulation, windows and doors. It may not include other items, though:

  • Heating and air conditioning may be extra expenses
  • A bathroom can add to the cost of a house extension
  • A kitchen adds to the cost
  • Quality inclusions will add to the cost
  • The cost will not include the cost of having plans drawn up or council fees
  • Furnishing the extension will add to the cost

A house extension is basically a waterproof shell. It will be ready to move in when finished, but will not include furnishings, blinds or curtains, lighting fixtures and other items. If a bathroom or kitchen is needed, the cost of plumbing and bathroom or kitchen fit outs has to be factored into the cost. How much will a bathroom or kitchen cost?

Other house extension costs to consider

A typical bathroom renovation costs:

  • $5000 to $15,000 for a budget bathroom
  • $15,000 to $25,000 for an average sized bathroom with mid-range fittings
  • $25,000+ for a high-end bathroom

Bathroom renovations include ripping out the old bathroom. If you're adding a home extension, bathroom builders won't have to tear out old fittings, but you will face other expenses. For example, the plumber will have to install pipes and sewerage. An electrician will have to install new wiring, lighting and outlets. Because of these expenses, a new bathroom may cost closer to the higher end of the scale.

A typical kitchen renovation costs:

  • $10,000 to $22,000 for a budget renovation
  • $22,000 to $35,000 for a mid-range kitchen
  • $35,000+ for a high-end kitchen

Like the bathroom, the cost won't include tearing out an old kitchen but will include new plumbing and electricity. You won't know how much a new kitchen will cost until you get quotes from kitchen installers, plumbers and electricians, but the cost will probably be higher than a kitchen renovation.

A bathroom or kitchen will be a greater expense than most other extra costs. If you feel your current kitchen is too small, what else would you use the space for? Think about ways to make it feel more spacious. Add larger windows or, if you don't have an open plan kitchen, knock out a wall to make the kitchen feel larger.

You may need a bathroom in a house extension, but how large does it need to be? If you already have a larger bathroom, an ensuite bathroom may be all you need. It will cost less than a large bathroom and may be perfect for the extension.

Consider all the house extension costs

Remember a house extension costs more than just the cost of the extension. Consider all the costs before you commit to an extension. Do you need 80m2 or will a smaller extension be within your budget? A 60m2 extension can save between $20,000 and $75,000 depending on the quality of inclusions. That amount of money can pay for most if not all of the furnishings, curtains and other inclusions.

Consider all the house extension costs

Do all your costings first and don't leave anything out. Remember to include:

  • Furnishings
  • Lighting
  • Curtains or blinds
  • Heating and air conditioning
  • Flooring
  • Painting
  • Exterior painting if needed
  • Excavation work

Check the quotes you receive from builders carefully. Do they include knocking out walls or excavation work? If not, those will be additional expenses. Some home extension builders will include everything in their quotes. If a quote is higher than another, it may include those costs. If in doubt, ask the builders what is included in their quotes and what is not included. A quote should list everything. If it does not, a builder may be trying to get your business by undercutting other builders. They will add other costs on later, though, so make sure you know what is in your quotes.

A house extension is not inexpensive, but moving to a larger house can be even more expensive. The house will cost more and you will have other expenses to think about. These will include:

  • Real estate agent's commission
  • Marketing the home
  • Conveyancing
  • Cleaning and/or styling your home
  • Possible repairs or renovations
  • Moving costs

Add up all the costs and a house extension is usually less expensive than moving. It can also be easier, since you don't have to leave the home while building is going on and can go about your daily business. As a bonus, if you decide to sell, the house extension can add its value or more to the cost of the home. Home extensions make good sense, both economically and for your peace of mind.

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