Cost of adding a second storey extension to your home

You’ve decided to increase your living space by going up, but what do you need to know to ensure that the extension is successful?

Article By: Style Plus | January 2017

Building a second storey extension is exciting. You have the opportunity to renovate the home you love into a larger one that better suits your family needs.



-  Jan Antoni Glinkowski • Director • Style Plus

How much space do you need?

How much space do you need?

A commonly asked question by our clients is “will one bedroom and ensuite bathroom cost less than three bedrooms and two bathrooms? The answer is yes it will. However, the additional cost to add those two extra bedrooms and one bathroom whilst you are building will be less than tackling them at a later date. This is the point where more thought is required at the planning stage.

Adding a second storey is going to be more costly than extening outwards at ground level. Whether you are adding one ensuite or three bedrooms and two bathrooms, there is still the same associated costs. For example:

• Structural

• Roofing

• Plumbing

• Electrical

• A new staircase

Tip: Planning your renovation is essential. This is when rough ideas become detailed plans with scaled drawings to guide your renovation. It can take a few attempts to get the plans absolutely right.

How much space do you need




How much will it cost

How much will it cost?

When considering extending upwards there are a number of factors that you will need to consider when setting your budget. You will also need to think about what you want to achieve. For example, do you want to change the style/modernise the look of the house or keep to sympathethic renovation?

For a medium to large second storey addition, plan around $200,000 to $450,000. The quality and price of construction materials and inclusions will make a difference and if the ground floor needs reinforcing to carry the load of the extension, it can add a substantial amount to the cost.

Have a contingency for those unexpected costs. For example you may have to undertake additional electrical work such as updating the fuse box or undertake additional plumbing. Your roof gutter system may also have to be reconfigured.

The cost of going up will always be higher than going out. This is mainly because the existing house will need to be strengthened and the work is being carried out at height that will require scaffolding and shrink wrap.

Architect & engineer for your second storey renovation

Architect & engineer for your second storey renovation

Finding an architect and engineer is one of the most important steps in your renovation process.

Typical questions from the architect are:

• Design features you want included

• The degree of changes you want to undertake? For example, basic, middle or extensive.

• How much you want to add on to your existing home in terms of floor space.

• The size of your budget.

Creating a second storey does mean adding extra weight to the existing house structure. You need to ensure that the building is able to handle the pressure as some older style homes are not structurally built to handle the extra weight. Therefore, an engineer’s assessment may be required to establish feasibility.

The first step in the process is to have detailed plans developed by an architect along with the engineer’s input.

Detailed plans at the start will help you understand what is realistic. For example, creating the second level will require a staircase. As a rule of thumb you will probably need to sacrifice a room on the ground floor to create enough space for the stairwell.

Finding an architect and engineer

Commonly asked questions for building a second storey

Commonly asked questions for building a second storey


• Is planning permission required? You will need a building consent, and possibly a resource consent, for additions and alterations, depending on the rules in your area.

• Will my second storey extension fit with my existing home? At Style Plus we pride ourselves on our design skills and our ability to produce high quality renovations which are sympathetic with your existing home.

• Do I need to move out whilst construction takes place? Generally this is recommended as it can mean extended delays as the Style Plus team work around you. Also there is the Health & Safety requirements.

• When can you start? At Style Plus, once the building consent has been approved, work can commence within approximately 4 - 6 weeks.

• How long should I expect the completion of the second storey build to take? The time period of the completion of the second storey build varies depending on the size and scope of the project. Style Plus 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.

• Can you help with my colour and finishing options? With so many options to select from and many decisions to make, Style Plus offers an interior design service that can assist you for all of the design choices.





Residential Building Warranty for Renovations

Undertaking a 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 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

Residential Building Warranty




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.

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