Home Extensions: The Ultimate Guide – 2022 Edition

A quality home extension or renovation can serve several important purposes. From making a space more aesthetically pleasing to offering improved functionality and extra room, to adding significant value, it is little wonder that more and more Australians are looking to make improvements to their homes.

JTDodd is a professional renovation business, known for specialising in value-increasing home transformations. We utilise our expertise and work with clients to make the process as smooth and enjoyable as possible.

For anyone planning to freshen up their home in 2021, the experts at JTDodd have compiled this handy guide. It will equip you with everything you need to know about the process, what to expect and how to get the best out of it.


Decide on a budget

Before commencing any new home renovation or extension project, you will need to decide exactly how much money you want to spend. This figure will act as an essential guide as you make many decisions, particularly in the preliminary stages.

Renovations vary significantly in terms of the associated costs. Some factors that will need to be taken into consideration include style, size, complexity, quality and timeframe. The best way to get a realistic idea of the price you can expect to pay for your specific project is to arrange a no-fee consultation with a builder. By asking a series of exploratory questions, they will work to determine how they can best support you in the construction of your extension or renovation.

By taking the time to discuss your distinct vision, requirements and goals, your builder will be in a strong position to consider all options and present recommendations for a tailored plan that will meet your needs. At this stage, your builder should also be able to provide a rough estimate of how much you should be expecting to spend, to ensure you get the results you are seeking. Your rough estimate will give you a crucial tool to help you decide whether your budget will cover the work needed before you move further into the process.

If you are planning to take out a loan to fund the work, you can use your rough estimate to kick start conversations about pre-approval with your bank.

Choose a builder

Because a home renovation or extension is such a significant investment, you will want to make sure you are working with a builder you trust. Of course, the price will factor into your decision, but selecting a contractor based on price alone is probably not the wisest move. Aside from a reasonable price tag, you will also want to ensure your builder is reliable and committed to high-quality workmanship.

To identify a suitable builder, there are several approaches you can take. You can start to draw up a long-list or potentials by jumping online and searching for fully-licensed, registered and insured practitioners in your area. As you do so, it is important to take a thorough look at their website, checking for positive testimonials and case studies of similar projects. Over and above this online research, you may also wish to consider speaking to friends, family or neighbours for their recommendations.

Once you have conducted your research, create a shortlist of three builders that you like the sound of. Once you have made your final choice, you can then ask your builder to develop a rough estimate. As outlined in the Decide on a budget section of this guide, the builder in question will probably ask to spend some time with you to discuss and understand your vision, upon which they can base their initial estimate. Once your rough estimate is provided, assuming you are comfortable with the costs, you can officially engage your builder to conduct the work. 

Of course, some property owners might prefer to start the process by engaging an architect and worry about finding a builder once all plans are drawn up. In these instances, architects can often make their recommendations of trusted builder contacts, and can even source quotes for you. These will be presented as what is known as a tender package.

In some instances, clients already know which builder they would like to work with, based on their past experience. If that is the case, you can simply set to work negotiating directly with the builder of your choice.

With your builder in place, the next step would be to talk through your vision and goals with an architect or designer (assuming you have not already started work with them earlier in the process). Once the plans are completed by your architect and all finer details such as fixtures and fittings have been decided, your builder will be able to develop a detailed fixed price quote. This quote takes into consideration size, quality and level of difficulty. It will give you the exact and final cost of your project. 


Preliminary work with your architect (Extensions)

If you are planning an extension, certain aspects of the project will mirror the process associated with building a new property, particularly in the planning. 

These early stages are likely to involve lots of back and forth between different professionals. Your architect or designer will develop working drawings (or construction drawings) that provide dimensioned and graphical information for use by the construction team and component suppliers going forward. These working drawings also offer all the detail relating to external and structural changes that need to be presented to the town planners at your local council, to allow them to assess the proposed work, before issuing the necessary permissions and permits.

Your town planning permit is a crucial aspect of the project because it will determine whether you can legally go ahead with the works. As the property owner, it is your responsibility to find out whether a permit is required before you start work on your extension. Before you go any further, it would make sense to find out about any specific requirements at your address by approaching the planning department at your local council directly.

During these initial planning stages, several other reports and plans will be required, including:

Soil report – Typically initiated and managed by the architect, a soil report involves an expert check of the soil upon which the extension is built. This is helpful for your architect and/or builder when determining things like how deep you’re going to need to dig, and what sort of footings (or concrete in the ground) you are going to need.

Engineering drawing – This is a type of technical drawing used to define the requirements of all engineering components. The primary purpose of an engineering drawing is to capture all features required from each of these components precisely, so the manufacturer or engineer can accurately produce them for you. Again, your architect should be able to engage the relevant expert to oversee this critical task.

Energy rating report – This report needs to be conducted by a certified energy consultant, and will determine the factors required to maintain a comfortable living environment inside the property. Organised by your architect, your energy rating report will consider factors including insulation, ventilation, glazing, size and climate. For sustainability reasons, all work in Victoria needs to meet a minimum 6-star performance standard. This requirement will be incorporated into all designs by your architect. Additional benefits of this work to the property owner going forward will include increased comfort, and money saved on power bills.



The aesthetics of your property are likely to be a reflection of you and your tastes. When it comes to planning how the inside of your new space is going to look, you will probably have a vision in mind. You will need to decide whether to do it yourself or engage an interior designer to realise your vision for you.

For the consultation and selection of colours, materials, fixtures and fittings (e.g. timber flooring, tapware, benchtops, splashbacks, sinks, basins etc.) that are going to make an impact, we would always recommend involving an expert, unless the interior design is a particular area of passion or skill for you.

Meanwhile, cabinetry design is sometimes incorporated into your architect’s drawings. However, if that is not the case, you can engage a draftsperson to work on this area of your renovation or extension project, after the initial plans are drawn up and before construction commences.


Getting Quotes

In the earliest stages of any construction project, your builder will work with you to develop what is known as a rough estimate. Based on the size, quality and complexity, this will offer an indication of the likely budget needed to complete your project. It tends to be calculated at a loose rate per m2.

After you have received your rough estimate, you will be asked by your builder to sign a Preliminary Building Agreement. This agreement is essentially a pre-contract document detailing all tasks required during the pre-construction stage. It might include:

  • Working drawings
  • Engineering drawings
  • Soil tests
  • Energy rating report

For more information on what each of these tasks involves, see the Preliminary work with your architect section of this guide.

Your Preliminary Building Agreement and all its associated tasks will need completing before your final building contract can be signed. Your builder and architect will work with you during this stage to make sure all your plans are achievable within the estimated budget.

There are two additional terms you’ll need to be familiar with at this stage…

A Prime cost item is an allowance made in your contract for the supply of materials. These might include benchtops, appliances, sinks, tiles or taps, amongst many other things. They are presented as dollar value amounts in your Preliminary Building Agreement, wherever the items in question are yet to be chosen. For instance, if you’re renovating your bathroom, you know you’re going to need a sink. Therefore, a Prime cost item for the cost of the sink needs to be included. You may still be mulling over exactly which sink you want to install, so an estimated or average figure will be listed against this element.

Prime cost items can be useful when allocating budget in the preliminary stages of a project, by offering an indication of the sorts of expenses you should expect to pay as the project progresses. The costs associated with these items are likely to change depending on your ultimate final selections. If you choose fixtures and fittings that are more expensive than the prime cost item, you will incur the additional costs. Associated budget blowouts can be avoided by making decisions about your fixtures and fittings early in the project. In an ideal world, this would occur before your building contract is signed.

A Provisional Sum is an allowance made in your building contract for the materials and labour associated with performing each specific task, i.e. plumbing. The Provisional Sum associated with each job will provide a good indication of the costs of all functions involved in the project. This can be useful information to have at your fingertips in the early stages when lots of important decisions are still to be made.

Just like Prime cost items, Provisional Sums are subject to change. Be aware that including lots of Provisional Sums in an estimate is a tactic used by some builders to make sure they can offer the lowest price and secure a job. The amount invoiced upon completion of the work can end up being far higher than the amount quoted using Provisional Sums, and you will be the one expected to foot the bill. For that reason, the more Provisional Sums that appear in your contract, the less risk and responsibility your builder is taking for any miscalculations or unexpected increases in price, and the more risk is passed onto you.

Getting a detailed fixed price quote is so important because it negates the need for Provisional Sums to be included in your contract. Your detailed fixed price quote considers all the factors impacting the cost of the project, including choice of materials, fixtures and fittings, labour, equipment and timeframe. It is this quote that will outline the final, accurate cost of your project, with all tasks and associated prices itemised.

Obtaining a detailed fixed price quote is not typically a free service. Getting your Preliminary Building Agreement and fixed price quote will generally cost somewhere in the region of $1,500. However, when asked whether this process is essential, our answer is always the same … you absolutely do! This thorough consultation with your builder and architect enables you to make informed choices relating to your budget throughout the process. Without this information to hand, you could find yourself having to pay unexpected extra costs as the project moves forward, and as your budget depletes you could be forced to sacrifice the quality of finish just to ensure the job gets completed.



One important question you’ll need to ask yourself before the commencement of any building works is, “Should I move out or stay put?” In the first instance, you’ll need to find out from your builder the extent of the work and potential disruption, and whether it is even feasible to remain at home for the full duration of the project.

Secondly, even if it is physically possible to remain in your property during the work, you’ll want to consider your comfort levels. Construction and renovation projects can create dust, debris and fumes. There can also be lots of excessive noise associated with the work. For these reasons, you may end up deciding to vacate and return only once the work has been completed.

Additionally, if you are having your bathroom or kitchen renovated and do not have a second one to use, moving into temporary accommodation until your facilities are functional again could be the best solution.

To help you make this decision, we’ve broken down several scenarios for your consideration:

  • If it is merely a bathroom renovation and you have a spare bathroom, there’s a high probability that you won’t need to move out.
  • If we need to remove an existing kitchen or bathroom and the process means your home is not habitable for a time, it is most likely you will need to move out for a short period.
  • If your extension is such that your house is left open and unsecured, you will be required to move out for a period of time.
  • If the liveability of your home is likely to be impacted for longer than what might be considered a minimal period, you may be required to move out for a short period.

You’ll also need to decide the timing of the work. When would be the best and most appropriate time for you and your family? Are you planning to host any events in your new space and, if so, when would everything need to be completed by? If you’re working backwards from a hard deadline, it always pays to work some extra buffer time into the plan. 

Once you’ve agreed on a preliminary start and finish date, your builder will provide you with a detailed construction schedule, so you’ll know what to expect and when.



Improving your home with a high-quality renovation or extension is a smart investment. It can enhance the general look and feel of your property, offer improved functionality or extra space, and will add significant value.

So, if you’ve been considering a home renovation or extension, there has never been a better time to get started! Contact JTDodd today to get the ball rolling with an initial, no-cost consultation.

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