Geotechnical Assessments

What is a Geotechnical Assessment

A geotechnical assessment is the process of evaluating the ground conditions at a development site to determine whether the soil and rock beneath the surface are suitable to support the proposed structures. It encompasses a range of activities, from desk-based reviews of geological data through to intrusive ground investigation, laboratory testing, and the interpretation of results into engineering design recommendations. 

Geotechnical assessments are essential wherever there is uncertainty about the ground conditions, where specific geotechnical hazards may be present (such as shrinkable clay, made ground, or dissolution features), or where engineering design parameters are needed for foundations, drainage systems, retaining structures, or earthworks. 

Common reasons for requiring a geotechnical assessment include: 

• Foundation design – determining bearing capacity, settlement characteristics, and the engineering parameters needed to design the most cost-effective foundation solution.

• Assessment of existing foundations – investigating subsidence, settlement, or structural cracking at established properties. 

• Drainage design – establishing whether the ground is suitable for infiltration-based sustainable drainage systems (SuDS) through soakaway testing and groundwater monitoring. 

• Planning and regulatory compliance – meeting conditions set by local planning authorities, building control, Lead Local Flood Authorities (LLFAs), and the Environment Agency. 

Why Geotechnical Assessments Matter 

A geotechnical assessment provides clarity on the ground conditions at your site a critical requirement for foundation design, drainage feasibility, and construction planning.  

Assessments are often requested by structural engineers, local planning authorities, and building control, and are essential for: 

• Designing safe, cost-effective, and compliant foundations 

• Avoiding unforeseen ground conditions during construction that cause costly delays 

• Establishing whether soakaways and infiltration drainage are feasible 

• Understanding seasonal groundwater levels and the risk of groundwater flooding 

• Meeting geotechnical planning conditions and NHBC or warranty provider requirements 
• Demonstrating compliance with Eurocode 7 (BS EN 1997) and relevant British Standards 

Without a proper understanding of the ground, there is a risk of foundation failure, excessive settlement, drainage problems, or unforeseen construction delays.  

Getting the right geotechnical information early in the project programme helps you and your design team make better decisions and reduce the risk of costly surprises. 

Our Geotechnical Assessment Services 

At Lustre Consulting, our consultants design bespoke assessment strategies tailored to your site and your project.  

We combine our geotechnical understanding with our environmental and contaminated land capabilities to deliver integrated geo-environmental assessments that save you time and money. 

Ground Investigation 

Our Geotechnical Ground Investigations provide the essential subsurface data needed to support foundation design and earthworks for developments of all scales.  

Using a range of intrusive methods best suited to the site and development proposals, our investigations are designed to characterise the ground conditions, identify potential geotechnical constraints, and provide actionable recommendations for your structural engineer. 

Learn more about Ground Investigations Services

Foundation Appraisal 

We appraise the findings of the geotechnical analysis and give preliminary design recommendations so the project engineer can select the most appropriate and cost-effective foundation solution for your development.  

From initial desk-based assessment through to detailed interpretation of ground investigation data, we calculate the bearing capacity of the ground, settlement analyses, and foundation design parameters in accordance with relevant British Standard guidance. 

Learn more about Foundation Appraisals

Groundwater Assessment 

A Groundwater Assessment provides monitoring data and technical analysis required to understand groundwater conditions at your site and how it could affect your development.  

Seasonal groundwater monitoring is increasingly required by Lead Local Flood Authorities (LLFAs) to establish peak groundwater levels and assess the risk of groundwater flooding, particularly where infiltration-based sustainable drainage systems (SuDS) are proposed.  

Our assessments inform drainage design, foundation detailing, and dewatering strategies. 

Learn more about Groundwater Assessments

Soakaway Testing 

Soakaway Testing provides infiltration rate data in accordance with BRE Digest 365 to support the design of soakaways and infiltration-based SuDS.  

Soakaway testing is routinely required by local planning authorities and LLFAs to demonstrate that infiltration drainage is feasible at your site.  

We undertake soakaway testing as a standalone service, or as part of a wider geotechnical or geo-environmental investigation, often in combination with our Groundwater Assessment service to check if groundwater levels could influence drainage design and SuDS. 

Learn more about Soakaway Testing (BRE365)