4. Garage Conversion.

When a garage is constructed, it does not have to meet the same requirements as a home under the Building Code and are therefore not suitable for habitable purposes i.e. non-habitable.

The conversion of a non-habitable space to a habitable space is considered an ‘alteration to an existing building’ rather than a ‘change of use’. The council requires that converted non-habitable spaces comply with the Building Code wherever possible to ensure that the homeowners live in a safe and healthy building.

A Garage Conversion is a good option if you want to add more living space to your home without extending the footprint of the house. However, there are a few council requirements for the conversion, for example,

basic single storey renovationAdditionally, due to the shortage of skilled, licensed builders and the ever increasing costs of materials, build costs are slowly rising.

So, for a ground floor, small single level extension, the indicative build cost at the lowest end of these estimates ($2,500/m2) for a 36m2 extension would be roughly $90,000 ex GST. This is your starting point and dose not include a bathroom, kitchen, architect and engineers fee, contingency fund and council  fees.

However, you will also need to add the following costs:

Until the plans are completed by the architect,  you will not know the exact cost of the home extension. When plans are completed, a more accurate quote can be presented to the homeowner.

TIP: When you receive a build cost quote, check if the following is included:

  • Building warranty cost. This may be part of the preliminary and general (P&G) costs.
  • Council costs.

Are There Any Complex Site Constraints?

As part of your home extension costs / project budget planning, you will need to include additional costs if any of the following apply:

  • Your soil type and ground conditions where an extension is planned may present more costly construction methods. This will usually mean that a geotechnical survey is required to obtain information on the physical properties of soil and rock around a site. The survey will also help to design earthworks and foundations for proposed structures.
  • Limited access to the site. Will it be easy for the builder to bring in materials, machinery and waste skips easily?
  • Is your house situated on a steep gradient that will make the renovation more challenging?
  • For the existing structure, are you removing any structural walls? are you building a second storey extension? If so, there will likely be additional costs for structural engineering and works.
  • Are you moving any plumbing or drainage? Rearranging the layout of the sink, shower or toilet (or all three) will most likely double, and in some cases triple, your plumbing/drainage costs.

Fixtures, Fittings and Finishes.

Fixtures, fittings and finishes are items that will form part of your renovation that are typically not itemised in your renovation building costs. These items are likely to add up to a significant portion of your renovation budget. However, they may be listed in your contact under as an estimate under a line item called Prime Cost items.

Prime Cost is a cost that is estimated for the purchase of specific items such as bathroom tap ware, door handles or even tiles. In general, homeowners select and source these PC items.

Alternatively, you might hire an interior designer such as Style Plus | Interior design to assist you with this aspect of your project.

Tip: Using Style Plus | Interior Design Service early in your renovation will help you avoid years of niggling regret from bad decisions made in isolation or under pressure. Our skilled interior designer will take the stress out of the selection process and ensures a consistent style. You can be confident your renovation will exceed the average and every detail will keep you smiling.

Where do I start?

Where do I start is a common question that we hear during our initial consultation with the homeowner.

The following is a typical Style Plus Renovations process that takes the homeowner to the start of the renovation build.

  1. Initial enquiry either phone or via the web site contact form.
  2. Site meeting with the client. This includes the project manager and architect.
  3. Review by project manager, builder and architect to determine if the project is feasible.
  4. A quote for the architectural services is emailed to the homeowner.
  5. Concept plans are created and discussed | accepted by the homeowner.
  6. A quote for the renovation based on the concept plans are presented to the homeowner.
  7. Final architectural plans are submitted for building consent.
  8. Building consent approved.
  9. A build contract is created based on approved plans
  10. Building contract accepted by homeowner.
  11. Initial deposit received.
  12. Construction start date is confirmed and agreed with the homeowner.

Frequently Asked Questions.

Do I need a building consent for my extension?2020-12-05T04:35:24+00:00

Do I need a building consent for my extension?

Yes, structural work, additions, alterations to your home require a building consent. A building consent is written approval from the council to carry out specific building work on a specific site. Typically, you will require an architect and engineer to assist you with your building consent request.

What is the cost difference between a ground floor extension and second storey extension?2020-04-18T05:07:47+00:00

What is the cost difference between a ground floor extension and second storey extension?

Yes there is cost difference between building a ground floor extension and building a second storey extension. The difference is between 40 – 60%. This difference equates to the additional structural engineering and additional work that is required to accommodate a second level on your home.

How Long To Build A Second Storey Extension?2020-04-18T04:44:40+00:00

How Long To Build A Second Storey Extension?

The time period of the completion of the second storey build varies depending on the size and scope of the project. Style Plus Renovations North Shore Auckland have project management processes in place to ensure high levels of efficiency in completing each stage of a job and strive to meet deadlines as best as possible.

Do I need to have insurance arranged?2020-04-18T08:55:32+00:00

Do I need to have insurance arranged?

Yes, definitely. We cannot emphasise enough how important insurance is. Your budget should always include an allowance for building insurance to safeguard your investment. We recommend insurance being in place from day one for the sake of your project reaching its completion no matter what may happen as the process takes place.

Thinking Of Renovating? Then contact us Now!


Whilst all information is considered to be true and correct at the date of publication, changes in circumstances after the time of publication may impact on the accuracy of the information. The information may change without notice and Style Plus is not in any way liable for the accuracy of any information printed and stored or in any way interpreted and used by a user.


About the Author:

Style Plus Renovations North Shore Auckland are an experienced team of knowledgeable experts who can take care of any build and renovation project. We are a New Zealand family owned and operated design, build and renovation company working predominantly within Auckland City and the North Shore, where we are based. We cater to a range of clients and provide an in-house interior design service as well as house renovations Auckland wide.


  1. Jan May 13, 2018 at 5:28 am - Reply

    I’m looking at building an extension.Great article and good sound advice.

    • Style Plus May 13, 2018 at 5:34 am - Reply

      Thanks Jan for your comment. We appreciate your feedback.

  2. JB June 22, 2018 at 10:52 am - Reply

    Very informative article. Are you not considering home insurance budget for the cost of renovation?

    • Style Plus June 23, 2018 at 1:21 am - Reply

      Hi JB. Thanks for the feedback. Appreciated. You are right. It should be in the article. However, we have decided Home insurance will be a separate article but with a link to other articles.
      Had a quick look at your site, looks great. I’m open to publishing other relevant industry bloggers articles.

  3. Style Plus September 6, 2018 at 8:59 pm - Reply

    Hi, thanks for your feedback, much appreciated. We strive to help clients understand the build process and products which are available.

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  7. LP Fabrication April 30, 2019 at 11:23 am - Reply

    Thanks, Antoni

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    • Style Plus April 30, 2019 at 8:15 pm - Reply

      Thanks for the comments. Are you an NZ company?

      • LP Fabrication May 2, 2019 at 5:17 am - Reply

        Absolutely! Proudly NZ owned and operated boutique furniture maker.

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