Specialists in Geotechnical Reporting, Sydney.
What is a Geotechnical Report?

A Geotechnical Report is a tool used to convey the features of the soil and rock materials on and underlying a site. Where underlying soil and rock materials are described this information is usually gained from subsurface ground testing taken at points spaced across the site. To an extent a Geotechnical Report is an interpretive document as the information gained from the test points is used to build a picture of the subsurface conditions across the whole site. The report provides design parameters  for the soil and rock materials found on the site. These parameters are usually used in footing design, retaining wall design and to determine the procedures required to safely carry out excavation. The report will also consider ground water conditions and its implications. Furthermore a Geotechnical Report describes and assesses the existing and potential hazards that could arise from slope instability and the hazards that could arise during the construction process at the earthworks stage. It also provides solutions to limit these hazards to acceptable risk levels.

In summary a Geotechnical report can be described as:
1. A summary of all ground related data both surface and subsurface.
2. An interpretation and analysis of this data.
3. A provision of site specific soil and rock engineering properties for design.
4. An assessment of potential ground related hazards on the site and solutions to reduce these hazards.

I am lodging a DA with council, do I need a Geotechnical Report?

  If you are lodging a DA with council, the local councils regulations will determine if you require a Geotechnical Report. Regulations vary slightly between councils but the issues that trigger the requirement for a Geotechnical report are generally as follows:

1. The property is on a steep slope.
2. A cliff face cuts or is close to the property.
3. There is a documented history of ground movement on the site or in the surrounding area.
4. The property falls within the potential landslip area as mapped by the local council. (Usually mapped as such due to points 1-3 above).
5. As part of the proposed development excavations are planned that extend beyond a depth of 2.0 to 3.0 metres (the depth requirement that triggers the need for a report varies between councils). 
6. As part of the proposed development excavations near the boundary are planned, where the distance from the ground surface to the base of the excavation (the excavation height) is greater than its closest horizontal distance to the boundary.

Why do I need a Geotechnical Report?

The most expensive problems to repair in construction usually occur during the earth works phase due to inadequate process and/or insufficient information. It is this phase of the construction a Geotechnical Report specifically focuses on, with an aim of minimising the risk of construction issues by providing methodology and process for ground works related construction and site specific information on the ground materials.

When should I get a Geotechnical Engineer to inspect my property?

If a geotechnical related problem is resolved quickly after its initial detection, potentially expensive remedial works can be avoided down the track. Many Geotechnical related issues become apparent after heavy rainfall or after a prolonged change in the local climate. Some of the indicators of potential Geotechnical issues include:

1.Any sign of ground movement.
2. New cracking appearing in walls or footings.
3. Small cracks or holes appearing in the land surface
4. Movement in retaining walls.
5. If an established tree begins to tilt.
6. A change in the usual direction or intensity of  a creek or other surface flow during heavy rainfall.
7. A change in the direction or in the volume of ground water seepage.
If you notice any of these issues on or near your property, we recommend you engage a Geotechnical Engineer to visit the property and assess the issue.

What is a DA?

DA stands for Development Application. If you plan to do any building or make changes to your property in the vast majority of cases you will need to lodge a DA with the local council. The DA is a checking process by the local council that ensures your proposal fits within their development guidelines. A Geotechnical Report is usually obtained prior to lodging a DA, once you have your plans done by an Architect or Draftsman. A development application is required for the following reasons:

  • Construction of new building or structure, including swimming pools, outbuildings, retaining wall, jetties, etc
  • Add or alter an existing building or structure
  • Demolish a building or structure
  • Display an advertising sign
  • Change the use of an existing building or land
  • Carry out excavation, earthworks or adding fill
  • Development on or near a heritage listed item
  • Development within a heritage conservation area
  • Subdivide land or strata subdivide a building