Geo-technical Reports (or Geotech reports) examine the conditions of the site you are building on and what lies beneath the surface. You may find that the soil is unstable because of soft subsoil or there are boulders in the area where you want to dig foundations. Geotech Reports are usually produced by drilling test boreholes, and then testing is done on the house site. Occasionally, other laboratory tests are also carried out on samples.
What is a Geotech Report?
The report is prepared by an experienced Geotechnical engineer, and contains information and analyses about the soil, rocks, and subsurface materials. The report includes data on ground bearing capacity, settlement and liquefaction. It also contains recommendations that structural engineers can use to design building foundations.
The final Geotech Report will then recommend the best foundations, and any stabilising methods that are needed. It will also provide recommendations on soakage, i.e. storm water drainage requirements.
What is covered by a Geotech Report?
It’s not always easy to answer this question. Sometimes, a simple soil report will suffice. Other times, a more detailed test is required and a lab is needed to analyse the samples. Geotechnical assessments of properties where construction is being planned have several different aspects. This includes:
GROUNDWATER
Assessing water table fluctuations and depth, as well as any geotechnical implications. Geotech reports don’t provide as much detail as stormwater designs, but they can give civil engineers useful information.
GEOGRAPHICAL INFORMATION
Identifying hazards, such as earthquake faultlines, landslides or sinkholes. Environmental contamination, or liquefaction zone. Depending on whether the area is susceptible to earthquakes, site-specific seismic design criteria may be needed.
SUBSURFACE
Investigating what lies underground includes testing the entire site, as well as the location of the building. You will be able to identify the soil composition and any necessary remedial work to stabilise the ground. The factors taken into account include bearing capacity and shear strength.
What will a Geotech Report Cost?
A simple Geotech report will generally cost $1800 – $3500. The main factor in the cost is the level of testing and analysis required.
If you are in an area known to have consistent good ground – such as Mid and South Canterbury/Central Otago – a simple ground investigation report verifying the ground is classed as ‘good ground’ may be adequate.
However, if geotechnical challenges are encountered, such as peat or uncontrolled fill, more testing may be needed. These reports can be higher depending on the size of the project.
You can ask your local council if a Geotechnical Report is required before applying for a building consent. This is usually part of the Building Consent Process
Our team will help you to create a Geotech report. To find out more, click HERE or call us to discuss.
