House extensions are the renovation of choice for homeowners who need more space, more function, or want to add more value to their home.
If you’re considering investing in an extension, there are a fair number of steps to take—many of them complex. We’re making it a little easier with this guide to some of the most common questions and solutions that you should know before breaking out the tools.
How much does an extension cost?
Extending your home can be as simple as adding an extra room or as complex as building an extra storey. As a result, there is a significant range in terms of total costs: Refresh Renovations suggests that an extension can cost anywhere between $60,000 and $200,0001, depending on your choice of materials and design. They provide the example of a same-level, one-bedroom addition as likely to run up about $60,000 in total.
This estimate is most significantly affected by the type of extension. Extending a kitchen or bathroom, which requires additional plumbing, electrical and gas work (for example) will increase the costs more than the simpler addition or extension of a lounge or bedroom.
Restricted access or unusual site conditions can remove the opportunity for certain construction methods and design choices. A section with a steep incline, for example, could mean that there simply isn’t enough support to extend your home in the way you want. A good architect or designer will be able to advise you on alternatives.
I’ve heard nightmare stories about “surprise costs”: what can I do about them?
It’s generally a good idea to factor in a 10 to 15 per cent “contingency budget” on top of your total costs2. This contingency ensures that your extension isn’t halted in its tracks by the need to gather more finance.
Site insurance is also a good idea (and sometimes required depending on your financing), as build sites are easy places for tools to get dropped and floors to get chipped. Your contractors (if you use them) are likely to have liability insurance as well, but this doesn’t cover every situation: invest in your own to ensure peace of mind.
Where can I get finance for my home extension?
Typically, banks will offer a form of construction loan, which is ideal for an extension or a renovation. Some institutions also offer the chance to draw on your existing equity for the build, or top up an existing home loan.
Borrowing for renovations is a little different from a regular home loan, so ensure you check with your preferred lender as early as possible to learn the caveats and requirements.
My costs are too high! Should I give up on an extension?
If costs are a concern, there are a few decisions you can make to get the most value out of the build. Some choices to consider include:
Acting as your own project manager
Compromising on the size/design of your extension
Compromising on the choice of materials
Choosing a same-level extension, rather than an upward extension.
Note that some of these money-saving strategies, particularly those that include replacing contractors with your own labour, can end up extending the build time significantly. Professionals are usually faster and create higher-quality extensions, but they also cost more—finding a balance is integral to good value.
Get your renovation planned and organised with the help of our free Home Renovation guide.
What kind of building professional should I hire?
Design is paramount to an effective home extension. Your choice in professionals include:
Architectural technicians
Architects
Specialist designers
Design teams at construction companies.
Each of these will have different qualifications and competencies, and may offer additional services. You can find more information on the types of building professionals and architects here.
An architect, for example, is likely the most-qualified person available and is perfect for complex or high-budget builds. They also often offer project management services. However, they may not be suitable for a simple extension, which could be dealt with through a design team at a construction firm (which will itself likely include an architecturally-trained person).
How can I plan for creature comforts?
Consider how you will keep the newly extended room comfortable: what heating source and level of insulation will you install? Both of these are particularly important if you are considering renting out or selling your home to an investor at some point in the future, as it will soon be law to have both heating and insulation that is up to standard.
In terms of heating, your options include:
Heat pumps
Solar heating
Central heating
Wood burners
Space heaters.
If you are already using one of these options, it may be more worthwhile expanding your existing system rather than investing in a new one. However, keep in mind that installing complete systems like central heating may incur additional costs due to the extra work required.
On a similar note, there is the decision of how the new extension will be lit. Nearly all designs will include some form of window, but you should also consider the impact of skylights as well as artificial lighting, and whether or not they would be a good option for you.
When do I get to pick my materials?
This stage is where you’ll be making more detailed decisions on your larger choices during the budget phase, particularly around materials: the core materials you use for joinery, framing, cladding, fixtures and fittings will need to fulfill a series of requirements. This includes structural strength and budget considerations, not to mention the actual look of the design.
The building professional you have hired should be able to assist with these decisions.
How can I avoid blowing the budget?
Solidify your vision before settling on a final plan. Every variation made to the design can extend the cost and the timeline of the extension, particularly if those changes impact electrical or plumbing work.
What can I do to speed up the build?
Get any consents you need from your local council well in advance. The process of releasing these consents can take time, and failing to get them in early can delay the start of work by weeks.
You should also aim to get a copy of your property file. This file will contain information on boundaries, conditions, services, flooding, surface coverage, right of ways, geotech requirements and more—information that could impact a home extension.
Often, the building professional you have hired can secure all the necessary documentation on your behalf.
Now that you’ve got a solid idea of the ins, outs and intricacies of the home extension process, it’s time to get started on the work itself.
Your design and build team will be able to advise you on the next steps, but generally you should be prepared with alternative accommodation during the build; being away from your home for the duration will make the work easier for your contractors as well as for yourself.
1. Refresh Renovations, 2016
2. Consumer Protection, 2018