When building a new home or making modifications that require new foundations, a geotechnical site classification is essential to ensure the structural integrity of your project. It helps prevent unexpected surprises during construction and optimises the design of your building. Unfortunately, it’s a step often overlooked, especially in smaller projects, but one that can save both time and money in the long run.
Why Do You Need a Geotechnical Site Investigation?
A structural engineer is responsible for designing the building’s structural elements, including the foundations. When working on a project, they often make assumptions about the soil conditions based on general knowledge of the area, the state of the property, or nearby construction projects. However, these assumptions may not always hold true.
Even if your neighbour recently had a geotechnical site classification done, it doesn’t guarantee that your property has the same soil conditions. Past excavations, fill materials, or variations in natural ground depth can significantly alter soil properties from one lot to another.
Consequences of Not Having a Geotechnical Site Classification
Without a geotechnical investigation, there’s a risk that the assumed soil conditions might be inaccurate. This can lead to major issues during the construction phase, such as:
• Incorrect Foundation Classification: If the actual soil conditions differ from the assumed conditions, the foundation design may be incorrect. This could require last-minute design changes, leading to unexpected delays and additional costs.
• Design Overcompensation: When soil conditions are unknown, structural engineers may design more conservative (and often more expensive) foundations to accommodate the unknown risk. By unlocking this information earlier, engineers can economise the design, potentially saving on material costs and labour.
• Missed Soil Hazards: A geotechnical investigation can reveal critical information such as soil moisture issues or the presence of acid sulphates, both of which can affect foundation stability. Identifying these issues early allows for more appropriate and cost-effective design solutions.
How It Works: Structural vs. Geotechnical Engineers
While a structural engineer designs your building’s foundation and other structural elements, a geotechnical engineer specialises in analysing soil conditions. The geotechnical engineer provides critical input that informs the structural engineer’s decisions.
By conducting a geotechnical site investigation, the geotechnical engineer can determine:
• The soil’s bearing capacity
• The depth and stability of the ground
• Potential moisture-related issues
• Presence of harmful chemicals like acid sulphates
This detailed analysis ensures that the structural engineer has accurate information, which ultimately leads to a more efficient and cost-effective foundation design.
The Importance of Upfront Costs
While the upfront cost of a geotechnical site investigation might seem unnecessary, it’s a valuable investment. Not only does it help reduce risks during construction, but it also gives the structural engineer the information needed to optimise the foundation design. Skipping this step might save money in the short term, but can lead to costly complications down the line.
Protect Your Project
At Blueprint Structural Engineers, we highly recommend carrying out a geotechnical site classification for all new residential projects or modifications requiring new foundations. By doing this early in the process, we can provide tailored foundation designs that are both safe and cost-effective, minimising risks and reducing unnecessary expenses later in the build.
If you’re embarking on a new project, don’t overlook the importance of soil investigation. Contact us today to ensure your project starts on the right foundation.
