As part of the Building Consent process when relocating a home, local councils often require a Geotechnical Report for building developments. It provides valuable information about the geological and soil conditions at the site, which is used to design safe and effective foundations. A well-prepared Geotechnical Report can save time and money by identifying potential issues before construction begins, and can help ensure the long-term stability and safety of your housing project.
Prepared by a geotechnical engineer (a professional with specialised knowledge of earth materials and their interaction with structures), the report is an essential component of any construction project that involves excavation, foundation work or other types of earthwork. In this article, we provide answers to some common questions about Geotech Reports.
Why do I need a Geotechnical Report?
You’ll need a Geotechnical Report to provide guidance on geological hazards, risks and limitations that may impede site development, including factors such as soft ground, slope stability, settlement risks, site excavations and liquefaction potential, among others. Most building consent applications require a Geotechnical Report for support, so you’ll need this to complete your project. Despite being a relatively minor expense in the overall development process, a Geotechnical Report can pay for itself by enabling informed foundation design.
What types of projects need a Geotechnical Report?
Geotechnical reports are usually required for a wide range of developments, including:
- Land Development – small and large scale subdivision
- Residential & Commercial – house relocations, multi-storey buildings, new dwelling, additions and alterations, remedial works
- Public Works and Infrastructure – roading, footpaths, pipelines
What’s included in a Geotechnical Report?
Geotechnical Reports typically include information on the geological and environmental conditions of the site, the testing and analysis methods used to assess the soil or rock beneath the site, a summary of the findings, and recommendations for foundation design and site development. It also includes details about any potential hazards or risks to the site (such as landslides or liquefaction) and suggestions for avoiding those risks. Additionally, the report may outline any regulations or requirements related to site development that should be considered.
How much does a Geotechnical Report cost?
Geotechnical Report costs can vary, given the uniqueness of each site and the customised scope of geotechnical services required to address specific site conditions and project size. However as a rough estimate, for a flat residential site the cost may fall between $1000 to $2000, whereas for a steep residential site, the cost can start from $2000 and go up.
What is the process to create a Geotechnical Report?
Conducting a site investigation of the property is usually required to prepare the Geotech Report. This investigation involves drilling one or more boreholes on the site, either by hand using a hand auger or by using a machine drilling rig. The soil samples collected from the borehole are documented in engineering terminology on a ‘borehole log’. The soil’s strength is also tested during the drilling process, and additional laboratory tests may be performed on the samples. The findings of the boreholes and testing will be used to assess the stability and foundation conditions of the site.