A ground investigation specialist characterises the ground beneath and around a development site through a phased programme of desk study, intrusive investigation and laboratory testing. Their Geotechnical Interpretive Report (GIR) provides the foundation designer, structural engineer and environmental consultant with the ground model they need to design safely and economically. They may hold Chartered Geologist (CGeol) status through the Geological Society or Chartered Engineer (CEng) status through the Institution of Civil Engineers.
What they do
- Conduct Phase 1 desk studies reviewing geology, historical land use and records
- Design and supervise intrusive investigation (boreholes, trial pits, window sampling)
- Carry out in-situ testing (standard penetration tests, dynamic probing, permeability tests)
- Commission laboratory testing of soil and rock samples
- Produce Geotechnical Interpretive Reports (GIR) and factual data reports
- Assess contaminated land and prepare remediation strategies
- Advise on foundation type, bearing capacity and settlement
- Carry out slope stability and retaining wall geotechnical assessments
When you need one
Ground investigation is needed whenever ground conditions are uncertain, potentially contaminated, or where ground risk could affect foundation design, slope stability or adjacent structures.
Typical costs (UK, 2025)
| Job type | Typical cost |
|---|---|
| Phase 1 desk study (single site) | £1,000 - £3,000 |
| Phase 2 investigation - single house plot | £2,000 - £6,000 |
| Phase 2 investigation - small development (up to 1 ha) | £8,000 - £25,000 |
| Contaminated land assessment (Phase 2) | £5,000 - £50,000+ |
| Geotechnical Interpretive Report (GIR) | £2,000 - £10,000 |
| Hourly rate (Chartered Geologist/Engineer) | £75 - £130 / hr |
Investigation costs vary with ground complexity, number of boreholes, depth, and extent of laboratory testing required. Remediation costs on contaminated sites are additional and can be substantial.
Qualifications to look for
The primary professional qualification for geologists in the UK. Requires a recognised geology degree, at least five years of relevant experience, and a professional review. Check membership at geolsoc.org.uk.
Many ground investigation specialists hold ICE chartership with a geotechnical specialism. The ICE also offers the Ground Engineering Panel (GEP) for those specialising in geotechnical work. Check membership at ice.org.uk.
A specialist qualification for practitioners working on contaminated land assessment and remediation. Required by many local planning authorities for signing off contaminated land reports.
How to find a reputable ground investigation specialist
Related Calculators
New Build Cost Calculator Extension Cost Calculator Retaining Wall Cost CalculatorFrequently asked questions
What does a ground investigation involve?
A ground investigation typically involves a desk study (review of historical maps, records and geology), followed by intrusive investigation - boreholes, trial pits or window sampling - to retrieve soil and rock samples. Laboratory testing then characterises the ground properties. The results are compiled into a Geotechnical Interpretive Report (GIR) that informs foundation design, slope stability, retaining wall design or contaminated land assessment.
How much does a ground investigation cost?
A Phase 1 desk study costs £1,000-£3,000. A Phase 2 intrusive investigation for a single house plot costs £2,000-£6,000. A larger residential development or commercial site investigation typically costs £8,000-£40,000 depending on site area, number of boreholes, depth and laboratory testing requirements. Contaminated land investigations add significantly to cost.
When do I need a ground investigation?
A ground investigation is required whenever the ground conditions are uncertain or potentially problematic. This includes new build on greenfield or brownfield land, extensions where foundation type is unknown, piling design, retaining wall design, slope stability assessment, contaminated land assessment and any site where subsidence, made ground, peat, mining or other ground risk is suspected.