Do I Need a Geotechnical Site Investigation?

geotechnical investigation, GCR

Understanding the Importance of Geotechnical Site Investigations

When planning any construction project, ensuring that the foundations are robust and reliable is crucial. Foundations, though often invisible, play a vital role in the stability and longevity of a building. Without proper support, buildings can suffer from subsidence, leading to unsightly cracks, sloping floors, or even structural collapse in extreme cases. This is where a geotechnical site investigation becomes essential.

The Role of Geotechnical Site Investigations in Foundation Design

A well-designed foundation depends on accurate ground information. A geotechnical site investigation helps us understand the ground’s nature, its strength, groundwater profile, soakaway potential, depth to bearing strata, and the presence of any potentially harmful contaminants. This critical information guides the design of the foundations and sub-structure, making it an indispensable part of the planning phase of any development project.

The Site Investigation Process

The site investigation process typically involves two main phases:

  1. Desktop Study: This initial phase involves reviewing existing geological maps, historical site data, and previous land use records to identify potential issues.
  2. Intrusive Groundwork and Testing: Following the desktop study, initial intrusive groundwork is carried out. This involves collecting samples and data points using methods such as hand pitting, windowless sampling, cable percussive drilling, and rotary coring. These samples are then analysed in a specialised laboratory, providing valuable data for designing the foundations.

Minimising Future Damage

Constructing without a proper understanding of the ground conditions can lead to numerous problems, including settlement, subsidence, soil volume changes due to moisture fluctuations, and slope stability failures. By conducting a thorough geotechnical site investigation, you can significantly minimise these risks, ensuring the long-term stability and safety of your building.

Enhancing Safety and Compliance

Geotechnical site investigations are not just about understanding soil mechanics; they also help identify potential hazards such as ground-borne gases or soil contaminants. These hazards can pose serious health risks or degrade the foundation’s integrity if not properly addressed. A comprehensive site investigation ensures that all potential issues are identified and mitigated, enhancing the overall safety and compliance of your project.

Tailored Solutions for Challenging Sites

On sites with known issues or challenging conditions, a geotechnical investigation is essential. Geotechnical engineers can identify risks and propose tailored solutions, which may include specific design adjustments, material choices, or site treatments. In some cases, it may even involve recommending a more suitable location for construction.

How Geotechnical Tests Are Conducted

Geotechnical tests involve the collection of samples and data points from both near-surface and deep soil structures. Techniques such as hand pitting, windowless sampling, cable percussive drilling, and rotary coring are employed to gather this data. The samples are analysed in a laboratory, and the results are interpreted by geotechnical engineers to inform the design of the foundations and overall structural plan.

Increasing Project Safety and Reducing Costs

A thorough site investigation can enhance the safety of construction projects, particularly in areas with complex soil conditions. By identifying potential risks early on, developers can avoid costly mistakes and ensure that their projects comply with safety regulations. Ultimately, a geotechnical site investigation can help lower overall project costs by preventing future structural issues and enhancing the project’s safety.


The importance of a geotechnical site investigation cannot be overstated. It provides crucial information that guides the design and construction of safe, reliable, and long-lasting buildings. Every developer should consider conducting a geotechnical site investigation for their next project. For more information or to discuss your specific needs, please contact GC Robertson.

Choose GC Robertson for comprehensive geotechnical site investigations and ensure the success and safety of your construction project. Visit our website at to learn more about our services and see examples of our past projects. For enquiries or to discuss potential collaborations, please email us at