How much does a house extension cost in New Zealand?

Adding a room or extending your living area on the ground floor are affordable ways of creating more space. Here are some key points to consider that will help you keep your house extension costs in check.

luxury home front extension
ARTICLE Stephanie Matheson

A same level house extension in New Zealand is likely to cost approximately $90,000 to $200,000+. Adding a room or extending your living area on the ground floor are affordable ways of creating more space. Here are some key points to consider that will help you keep your renovation costs in check.

How much should I budget for on a house extension?

Ground floor extensions are typically more affordable than converting the loft or excavating basement space. Renovation costs for a same level extension are roughly between $90,000 and $200,000 depending on your materials, labour and project management. As a rough guideline, earmark around $90,000+ for a one-bedroom addition to your home. Smaller renovations may work out slightly more expensive per square metre than larger renovations as many of the overheads such as council permits stay the same. It’s best to get a fixed price from your renovation consultant before the project starts to ensure your renovation comes in on budget. If your budget is tight, focus on the things you really need and start a list of possible ‘wants’ to add to your home further down the track.
Early estimates from your chosen building provider are usually a guideline based on a series of assumptions. Even when you get the actual quote, plan in a contingency budget of at least 15% for unforeseen problems and extras. This will help you cover expenses such as having to repair leaks or taking care of structural problems without jeopardising your renovation project.
Your builders will work from architectural plans. Major building work typically requires Building Consent from the council and in addition Resource Consent may be required. Your architectural designer or building project manager should be able to let you know if you need this. Once the drawings for your project have been accepted by council changes become very hard to implement.
Concept Drawings of a renovation are very useful. They show you what your finished renovation will look like. While they may be a little more expensive than line drawings, they help save money in the long run as the likelihood of having to change or alter your plans further down the track is reduced.

Cost of a one-bedroom extension

From $90,000
To get an idea of the costs, duration and specifications included within an extension in this price range, check out this bedroom addition in Wanaka.

How can I create open-plan living?

An open-plan layout with good indoor-outdoor flow is a great way of creating the perception of more space. One of the most common alterations is the creation of one large living/dining/kitchen space. Opening up walls is usually a straightforward process, however, load-bearing walls may need to be strengthened which would incur additional costs. Any electrical or plumbing points within the wall would also have an impact on the overall cost. If you are looking to simply remove a non-load-bearing wall between two rooms, you may be able to get this taken out and tidied within one day.
For further inspiration, check out this open plan kitchen renovation in Wellington - completed for $80,000.

How can I create indoor-outdoor flow?

Sliding doors are a practical option for most room layouts and scenarios, and offer easy outdoor access from living rooms and bedrooms. They don’t open up completely, as would bi-fold or French doors, but they do allow for controlled ventilation as they can be opened fully or partially. The two standard types of sliding doors are top hung or bottom rolling systems. Top hung doors allow the bottom sill to be completely flush, however, they often require increased lintel support and installation generally takes longer, which means additional costs. Bottom rolling systems are ideal for larger, heavier glass panels. If you plan on adding a wooden deck to your extension, you should factor in anywhere from $450 per square metre for this.
Windows and doors in a new extension need to be double glazed. It might also be worth retrofitting double glazed windows in the rest of your home. This could cost anywhere from $18,000 for a small three-bedroom home, but will be more expensive if joinery needs to be replaced too.
Check out this $53,600 deck renovation in Queenstown for further inspiration.

How can I warm up my home?

Insulation is a must these days, as it helps create a space that is less prone to condensation and easier to heat. Most heat is lost through the roof (about 42%), so that should be a top priority for your extension. About 24% of heat is lost through the walls, and 20% through the floor. If you’re using a frame construction system insulation material should be placed within the wall framing. If your existing home is not insulated, consider if your renovation project is a good time to address this issue. You should be able to insulate an average three-bedroom house for $5,000+ (ceiling and floor depending on grade).
Depending on the design and style of your extension, one of the easiest and most cost-effective ways to install heating is adding an electric heat pump. It’s important to get a unit that is correctly sized for your space so that you don’t waste energy and money. Using passive solar energy can be a major money saver and help keep your home healthy and comfortable. Ask your renovation consultant at the outset of your project for options that maximise the use of direct sunlight. For example, large eaves may help let the low winter sun into your home while keeping the sun out in summer.

Cost to insulate a standard 3 bedroom home

From $5,000+
Take a look at our “Warm Up” case studies for ideas.

Do I need to re-clad my home when doing a house extension?

In most cases, when you are extending your home you will be able to keep all the original cladding on your house and simply add the same style of cladding to your addition so it blends in perfectly. Painting the exterior of an average-sized, single-storey house with a one-room extension is likely to cost around $20,000.
If you do need to replace your cladding, take a look at our house re-cladding case studies for pricing and options for the different materials available. The right kind of cladding will keep your home weathertight and good looking for years to come. Timber has long been the cladding of choice in New Zealand as it’s extremely resilient and versatile. Cedar is often left unpainted while other woods need to be repainted or stained on a regular basis, thus incurring regular maintenance costs. Man-made weatherboards may be a suitable and budget-friendly alternative. They are low-maintenance and come in horizontal and vertical styles. All you will need to do to maintain your home is to give it an occasional wash.

Cost to re-paint a single-storey home

From $20,000
Take a look at our re-cladding projects for inspiration.

How to save money on the interior finish when doing a house extension

Getting your new room’s walls, ceiling and flooring finished is the final step of your renovation project. If your budget is tight, focus on a basic but quality finish. You can always add custom touches and upgrade any trim and mouldings along with decorative hardware later on. When it comes to flooring, synthetic carpet or wooden laminates will be your most affordable options.

This article explores options ideas and costs for a same-level home extension. You may also want to read our dormer extension price guide, second storey addition or loft conversion price guide or basement conversion price guide.

Get in touch with Refresh to discuss your house extension project

If you would like to discuss options and ideas for your house extension project, please use the enquiry form on this page to provide us with your contact details. We will get in touch with you at a time that suits you to discuss your project. If you would like to provide us with more information about your project, we have a more comprehensive enquiry form on our "Get in touch" page too.
The costs within this article are rough estimates and are subject to change. For a quote accurate to your specific project, please consult your local renovation specialist.

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