How much does an excavation project or basement conversion cost in Auckland?

Transforming a basement area can take a basement from a lifeless, cold, damp space into a great space suitable for a number of uses.


Article By: Style Plus | June 2016
Planning your excavation renovation project

Planning Your Excavation Renovation Project or Basement Conversion

Planning Your Excavation Renovation Project or Basement Conversion

As with any renovation, planning is the key to a successful project. This type of project requires very careful planning especially with regards to health and safety aspects of the works.

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

Typically, a number of factors need to be considered during the planning stage in order to create exactly the right type of space. These include:

• What consents will be required?

• Will drainage be an issue?

• Is your home of a 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 lighting is available?

• Does the basement need to have internal or external access?

• Would you like to add a bathroom?

Planning Your Excavation Renovation Project

Concepts & Design

Concepts & Design

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 is able to 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 design process.

Concepts & Design

Earthworks & Foundations

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 steel work 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, a site which is relatively close to a tip site, a 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.

• Architect & Engineering.
• Earthworks & Foundations.

SquareTomato - Architects

Heating & ventilation

Heating & ventilation

If you plan on creating a new living space for the 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; 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 vary based on specifications and the cost of installation varies more than the units themselves and can be anything from $725 to $1400.

• DVS.
• HRV.
• Heat Pumps.

Heating and ventilation

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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