Demystifying Basement Renovation Costs: A Quick Guide


How Much Does A Basement Renovation Cost In Auckland?

A basement renovation | conversion can take a basement from a lifeless, cold, damp space into a great space suitable for a number of uses.

So, what are the basement renovation costs in Auckland?

Developing a basement area is a major renovation and logistically quite challenging. However, it could potentially, double the size of your home and add value to your property. Creating this additional space will allow you to make endless options on it’s usage.

The team at Style Plus Renovations North Shore Auckland shed some light on the basement renovation | conversion process and basement renovation costs:

  • Planning Your Basement Renovation | Conversion.
  • Basement Concepts & Design.
  • Basement Earthworks & Foundations.
  • Retaining Walls.
  • What Do I Need For My Basement Heating & Ventilation?
  • What Are The Council Requirements?
Basement renovation

Planning Your Basement Renovation | Conversion

Before any work is undertaken, engineering reports are required for both the structural and geotechnical aspects. These reports provide insight into any stability issues before the start of the works.

Typically, several factors need to be considered during the basement planning stage to create exactly the right type of space. These include:

  • Will my space be a ‘habitable space’?
  • What consents will be required?
  • Do I require Resource Consent for my conversion?
  • Will drainage be an issue?
  • Is your home of suitable construction and design which makes it suitable for an excavation renovation project or basement conversion?
  • Is the basement area dry or damp?
  • How much headroom is available?
  • What would you like the space to be used for?
  • How much natural light is available?
  • What are my additional power/electrical requirements?
  • What are my additional plumbing requirements?
  • Does the basement conversion need to have internal or external access?
  • Would you like to add a bathroom?
  • Reviewing at a high level the basement renovation costs.

When it comes to planning your renovation project budget you should look at allocating around $350,000 to $500,000+. These figures are approximate for excavation renovations and basement conversion costs.

Typically, under-house conversions can vary greatly in terms of costs. Job estimates and timelines are normally provided on a case-by-case basis.


Concepts & Design For Your Basement Renovation

After you have gathered your thoughts on what the new space will be used for, you will need to engage an experienced architect to create the plans for your renovation.

Using concept plans, the client can see on paper what the project would look like and enable an estimate for the works to be created.

If the new space requires excavation, structural and foundation work, typically the council will require a Structural Engineering Report and Geotechnical Report or Soil Report to be provided as part of the Building Consent process.

The Geotechnical Report also provides the structural engineer and architect with information to help in the basement design process.


Earthworks & Foundations

Basement renovation | conversion costs will include earthworks & foundations.

Excavation means removing dirt and concrete and making new concrete footings below the existing ones then pouring a new concrete slab floor.

If you are creating a new basement where there was only a crawl space, or if your existing foundation is not structurally adequate, it may require lifting your house while the new foundation walls are built and the foundation slab poured. Additional steelwork may also be required as part of the structural engineering works.

When it comes to the cost of earthmoving, the budgeted cost may vary depending on the specific conditions of your site and its proximity to a tip site.

For example, at a site which is relatively close to a tip site, bulk excavation and tip would cost around $70+GST per cubic metre. This cost does vary due to other factors such as site access, type of excavation machinery used and level of difficulty in excavation.

Basement concrete blockwork masonry walls which are below ground are structural retaining walls. Any part of these walls that is below ground level must be made waterproof by the application of a damp proofing membrane so that ground moisture cannot penetrate.

Typically, below-ground damp proof membranes come in the following forms:

  • Liquid coatings (bitumen or tar emulsions, epoxies, polyurethanes and modified cement or bitumen).
  • Modified bitumen-based sheet (self-adhesive and torch-on).

Once the blockwork is completed an adequate drainage systems should incorporated to prevent groundwater accumulating against the basement concrete blockwork masonry walls.


Retaining Walls

Apart from the blockwork retaining, there may also be a requirement for a retaining wall around the house. Retaining walls that are over 1.5m high and those supporting a surcharge require building consent.

‘Surcharge’ Any added weight above a wall is called a surcharge. For example, driveways, and patios are common surcharges.

A retaining wall has to be strong enough to support a load of soil pressing against it. This load determines the size of poles and the thickness of retaining timber to be used so that the poles or timber do not break.

The important part of the retaining wall is the part below the surface which anchors it. If the footings, foundations or the soil is weak then there is nothing stopping it from falling over.

One of the key things is to drain water from behind the retaining wall. If a retaining wall does not drain well then the bank behind and footings can become waterlogged and the retaining wall can fall over.

Soil types can have a significant effect on how a retaining wall performs. This is where the Geotechnical Report is required to calculate the type of retaining wall to be built. 

At Style Plus Renovations, we recommend that the advice of a suitably qualified chartered engineer should be obtained to design your retaining wall which is over 1.5m high or a retaining wall less than 1.5m high but with a surcharge.



When it comes to lighting your new basement area, during your renovation planning stage you will need to consider its use first and specification. For example:

  • What will the new basement ceiling height be when it is completed?
  • How will you use your new basement area?
  • Will it be just a laundry or storage room?
  • Will it be a family living room?

Whatever its functional use, if you are in a situation where there will be little natural daylight you will need some special basement lighting ideas.

First of all, wall colour plays an important part in maximising the natural light you have. Light-coloured walls and surfaces help maximise natural light by providing a reflective surface.

Next are the actual light fittings. There is a wide range of light fittings to choose from. At Style Plus Renovations, our preferred light fittings are LED’s. LED lights can replace fluorescent and incandescent bulbs in the house.

LED lights are able to produce more light than an average bulb even with a smaller wattage.

The light emitted by an LED is not affected by the wattage of the bulb, and even by its size or shape unlike incandescent or fluorescent bulbs. Additionally, an LED has the capacity to produce a coloured light without using any filter or any covers that conventional lights use. 

Therefore, if you want to have a lighting system in your house that can also have a decorative effect, then an LED lightbulb can be the best option that you can take.

There is a range of dimmable LED options available. It is best to check the packaging and also ensure your dimmer switch is compatible with the dimmable LED bulb.

LED lighting has the benefit of more efficient lighting to save more on your energy consumption. You may want to consider replacing all of your house lights with LED’s when you undertake your renovation.

The average cost for replacing existing halogen or incandescent recessed downlights with LED lighting is around $85 per light (based on 4 or more lights being replaced and whether the existing light can be replaced).

At Style Plus Renovations, we suggest that a site visit is undertaken by a qualified, licensed electrician to review your current lighting system and to provide a quote.


Heating & Ventilation

If you plan on creating a new living space for teenagers or have full-time occupied bedrooms, you will want the area to be well-ventilated and warm, especially during the winter months. Ventilation should be considered early in your design process.

A good design should have a balance between the requirement to introduce fresh air into your basement space and the need to maintain comfortable temperatures. Additionally, ventilation should be considered alongside passive heating and passive cooling options (solar, windows and walls).

If you consider heating without ventilation, you may end up with a basement space that is warm but not as healthy or comfortable as it could be.

Typical systems that you could install include; a direct ventilation system, a heat pump unit or underfloor heating.

Direct ventilation systems such as DVS and HRV consist of a fan mounted in the roof space. The system forces dry filtered air from the roof space through a system of ducts into the living areas of the house. This creates positive air pressure which forces moisture-laden air out through gaps in the building envelope. The cost starts from $5,000.

Other than passive solar, heat pumps are among the most energy-efficient forms of heating available. Heat pumps come in various sizes, from single-room heaters to ducted whole-house systems. It is important to get a pump that is the right size for the area to be heated. Installation costs can be significant.

The cost of heat pumps varies based on specifications and the cost of installation varies more than the units themselves and can be anything from $800 to $1,500 depending on the job specification.


What Are The Council Requirements?

If the new space requires excavation, structural and foundation work, typically the council will require a structural engineering report and Geotechnical Report or Soil Report to be provided as part of the Building Consent process.

The Geotechnical Report also provides the structural engineer and architect with information to help in the design process.

Typical engineers report/observations would include:

  • Foundations including point loads.
  • Concrete slab including moisture control.
  • Concrete block work.
  • Support posts.
  • Beams including floor joists.
  • Connections.
  • Internal stair case.


  • Do I require building consent for my basement conversion?
    Some conversion/renovation work may require a building consent. For example, installing a small wet bathroom requires consent. Also, any work involving load-bearing walls and bracing will also necessitate the services of a chartered professional engineer or registered architect. Note - even when a building consent is not required, all work must still comply with the Building Act and the Building Code.
  • Do you have to move out during the basement renovation?
    This depends on a number of safety factors and site risk assessment. However, moving out is rarely necessary when converting a basement in our experience, unless significant structural work is required.
  • How long would a basement conversion take?
    It depends on many factors. For example, it could take anywhere from 1 to 3 months, depending on the amount of engineering work required based on the proposed basement footprint.
  • Can any type of basement be converted?
    Due to the complexities of the site, not all basement spaces are suitable for conversion into living spaces.


Basement Conversions

Basement renovation conversions offer outstanding opportunities to create extra storage space, home gyms, or convenient home office spaces, particularly for individuals who are self-employed or have the flexibility to work from home.

Read More »


As an Auckland North Shore family-owned and run business, Style Plus Renovations cares about what we do and we take the time to fully understand your renovation needs. We are also proud to receive some exceptional compliments from our Auckland clients.

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Tel us about your renovation project and we’ll call you back for a no-obligation chat about your ideas.

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We look forward to hearing from you to discuss your project and get you started on your renovation journey.

If you would like to know more about our renovation process, check it out here.

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