Home Extension Renovation Costs 2018

Adding a room or extending your ground level living area are cost effective ways of creating more space. However, what are the home extension renovation costs when embarking on this type of renovation?

The team at Style Plus | Renovations Auckland take a look at some of the costs behind building a single level home extension:

  • So why renovate?
  • What are the costs to build an extension?
  • A basic single story (same level) extension example.
  • Does the quote include a kitchen or bathroom?
  • Finishes & Fittings.
  • Are there any complex site constraints?
  • Residential Building Warranty for Renovations.

A home extension is a popular option for home owners needing more space but not wanting the daunting task of purchasing an older property to fully renovate.

–  Jan Antoni Glinkowski • Director • Style Plus

why renovate

So Why Renovate?

Renovating your home in the way you choose is one the great benefits of owning your own property. However, what are the common reasons to renovate?

A few common reason are:

  • You would like to move, however, the property prices mean the best option is making your current home work for your family.
  • You would like to stay in the area where your preferred schools are.
  • Where you can grow into a property such as adding extra space such a single level extension to accommodate an expanding or growing family, or to simply add a sense of space.
  • Adding more living space to increase your return on investment.

Renovating your home can improve your lifestyle, add value to your property and above all it adds an enormous sense of satisfaction. However, before you start on the renovation path there are a number of costs to consider.

Click here to read 20 home renovation tips and ideas 2018

A Basic Single Story (Same Level) Extension Example

In Auckland a more realistic estimate for a house extension costs could be between $2,600 – $3,800+ per m2. Due to the shortage of skilled, licensed builders and the ever increasing costs of materials these meter square rates are slowly rising.

So, for a ground floor single level 4x5m extension, the indicative build cost at the lowest end of these estimates would be roughly $50,000 ex GST. However, you will also need to add the following costs:

  • Professional fees. For example, architect fees for preliminary | building consent drawings and structural engineer services.
  • Plan a contingency fund. Renovations have a habit of revealing hidden surprises. Allow at least 10% for overruns, unforeseen costs or changes to the plan.
  • Add GST.

TIP: When you receive a build cost quote, check if the building warranty cost is included. This may be part of the preliminary and general costs. Also check if the council costs are also included.

basic single storey renovation
style plus renovation quote

Does The Quote Include A Kitchen Or Bathroom?

As the design of a kitchen is unique to the home owner the actual cost may not be included. However, a provisional sum may be included in your build contract as a ballpark allowance.

Bathrooms: Add $20,000+ for a mid-range bathroom. Costs may be more depending on your bathroom ware and finishes.

Kitchens: Add $30,000+ for a mid-range kitchen. This completely depends on your specification.

Tip: Modular (kit set) kitchen suppliers work with set sized cabinets. Their approach is to do a “best fit” from within their standard range and then use filler panels to fill the gaps. Custom made kitchens offer better use of space and are designed and fitted to your specification.

Finishes & Fittings

The above cost estimate assumes modest finishes, fittings, electrics and lighting. For example simple painted walls, carpet floors or possibly laminated flooring.

Tip: Always check with your builder what the level of finishing will be. It is best to know earlier than be surprised by the addition variation costs at a later stage.

If you are wanting high end finishes such as engineered wood floor finishes, custom fitted joinery, these costs will increase your budget.

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.

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?
  • For the existing structure, are you removing any structural walls? 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 costs.
any renovation constraints
stamford building warranty

10 Year Building Warranty

Undertaking a home renovation is one of the biggest investments you will make so it is important to have a building warranty which protects you both during construction and for 10 years after completion.

Our 10 year Residential Building Warranty provided by Stamford Insurance has been designed to cover any type of new development, from individual homes to larger sub-divisions and multiple housing units.

Stamford Insurance – 10 Year Building Warranty

This article is also available in SlideShare:

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.

By |2018-09-23T00:27:38+00:00March 23rd, 2018|Categories: Renovations|8 Comments

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. Claire Metcalfe September 6, 2018 at 9:05 am - Reply

    A nice blog you have shared with us all and it is very knowledgeable, aware about something which we don’t know. I am very thankful for your post so much.

    • 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.

  4. Eric McDonald October 13, 2018 at 5:13 am - Reply

    I am really impressed with your article and I will share this as much as it will be possible for me because It’s really a good post.

  5. Emma Jennifer October 13, 2018 at 5:51 am - Reply

    In this post you are very thoughtful . I am very happy to read this post. It’s so motivational post for me. I would like to very thankful for this best and most important information.

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