Who signs a geotechnical design report under Eurocode 7
The investigation report presents the data. The design report states the design values and carries responsibility. Here is how the two differ and what the appointment should say.
Eurocode 7 draws a line that most appointment documents blur. The ground investigation report presents the factual data and the derived values obtained from it. The geotechnical design report states the design assumptions, the design values of ground properties, the calculations and the supervision and monitoring regime, and it is the document that carries design responsibility. The drilling contractor can produce the first. Only a geotechnical designer can sign the second.
On a development site the practical question is who that designer is, and whether the appointment actually says so.
The reports the code distinguishes
Eurocode 7 sets out the content of a ground investigation report and the content of a geotechnical design report, and they answer different questions.
The ground investigation report presents what was found: the investigation methods, borehole and trial pit records, field test results, laboratory test results, groundwater observations, and a factual account of the ground and groundwater conditions. It may also present derived values of geotechnical parameters, with the basis for their derivation.
The geotechnical design report goes further. It describes the site and its surroundings, the ground conditions, the proposed construction and the actions on it, the design values of ground properties with justification, the codes and standards applied, a statement on the suitability of the site, the calculations and drawings, the foundation recommendations, and a plan of supervision, monitoring and maintenance.
That last item is routinely omitted. A design report without a supervision and monitoring plan is incomplete against the code, and on a site with variable ground it is the part that protects everyone.
Investigation report against design report
| Ground investigation report | Geotechnical design report | |
|---|---|---|
| Primary content | Factual records and test results | Design assumptions, values and calculations |
| Derived or design values | Derived values, with basis | Design values, with justification |
| Supervision and monitoring | Not required | Required as a plan |
| Who typically produces it | Investigation contractor or consultant | Geotechnical designer |
| Carries design responsibility | No | Yes |
The confusion arises because a single consultancy often produces both, bound into one document with an interpretive section in the middle. That is fine, provided the design content is identifiable and signed. It is not fine when an interpretive report offering foundation recommendations is presented as factual work by someone who has not taken design responsibility for the parameters.
Who takes responsibility for the parameters
Design values are chosen, not measured. Moving from a scatter of test results to a characteristic value involves judgement about the volume of ground governing the behaviour, the variability of the data, the quality of the sampling and the failure mechanism being considered.
The person exercising that judgement is the designer, and they should be named. Ask for the report to state who selected the characteristic values and on what basis, and expect a statement rather than a table.
Where the structural engineer designs the foundations using parameters from a geotechnical consultant, responsibility is shared and the interface has to be explicit. Who owns the settlement assumption? Who owns the bearing resistance? Ambiguity here surfaces years later, which is why the appointment wording matters more than the report format.
Geotechnical categories and the skill they need
Eurocode 7 sets three categories, and they are a proportionality tool rather than a bureaucratic one.
Category 1 covers small and relatively simple structures where the risk is negligible and the ground conditions are known from comparable local experience. Qualitative work and routine methods are enough.
Category 2 covers conventional structures with no exceptional risk or unusual ground, which is most housing and most commercial development. It requires quantitative data and analysis, and a designer competent in routine geotechnical design.
Category 3 covers very large or unusual structures, structures involving abnormal risks, and unusual or exceptionally difficult ground. Deep basements, tall buildings on variable ground, sites over old workings or on slopes at risk of instability tend to land here, and they need a specialist with the relevant experience, not simply a chartered engineer.
Assign the category early and record the reasoning, because it determines the investigation scope. A category 3 problem investigated to a category 2 scope produces a design report whose assumptions nobody can defend.
Checking and independent review
For anything above the simplest work, independent checking is worth having, and in some situations it is required.
In several London boroughs a basement proposal must be accompanied by an independent audit of the geotechnical and hydrogeological work, carried out by a suitably qualified engineer instructed separately. That requirement flows from local policy rather than from the code, and it should be built into the programme and the budget from the outset. The Basement Impact Assessment is where that material comes together for the planning application.
Even where no audit is required, a second pair of eyes on the characteristic value selection costs little relative to the consequences. Ask the reviewer to comment specifically on the parameters and the failure mechanisms considered, not on the report as a whole.
For verifying individual competence, the register of ground engineering professionals maintained by the Institution of Civil Engineers grades individuals by role, and it distinguishes between advising, specialist practice and full professional responsibility. Ask for the grade and the scope, not just chartered status. Briefing a specialist when the site data is incomplete covers how to set that appointment up.
Interaction with the structural designer
The handover is where projects lose money. Three things should be agreed in writing before the design report is issued.
- The design situations to be covered, including temporary works, construction sequence and any phased loading.
- The limit states to be verified and which party verifies each, with the design approach and partial factors stated.
- The serviceability criteria, particularly the settlement and differential settlement limits the structure can tolerate.
Where temporary works are excluded from the geotechnical scope, say so on the face of the report. A design report silent on the temporary condition will be read by a contractor as covering it.
What to require in the appointment
Write the deliverables into the appointment rather than relying on a proposal letter.
- The geotechnical category assigned, and who may change it
- A ground investigation report and a separate, identifiable geotechnical design report
- The named individual taking design responsibility, with their register grade
- A statement of the basis for characteristic value selection
- A supervision, monitoring and maintenance plan
- Whether temporary works are in or out of scope
- Whether an independent audit is required by local policy, and who instructs it
- Which generation of the Eurocode the design follows, since the standards are being revised and a mixed set of assumptions across a project team is a real risk
A Geotechnical Assessment for the planning application is a summary of this work, not a substitute for it, and professional review can be arranged through the professional directory.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.
Frequently asked questions
What is the difference between a ground investigation report and a geotechnical design report?
The investigation report presents factual records, field and laboratory results and groundwater observations, and may give derived values with their basis. The design report states design values with justification, the calculations, the foundation recommendations and a plan of supervision, monitoring and maintenance. Only the second carries design responsibility.
Who chooses the characteristic values?
The geotechnical designer, and they should be named in the report. Moving from test results to a characteristic value involves judgement about the governing volume of ground, data variability, sampling quality and the failure mechanism considered. Ask for a written statement of that basis rather than a table of numbers.
What are geotechnical categories for?
Proportionality. Category 1 covers small, simple structures with negligible risk and known local ground. Category 2 covers conventional structures with no unusual risk, which is most development. Category 3 covers large or unusual structures, abnormal risks and difficult ground, and needs a specialist with relevant experience.
Is an independent audit of geotechnical work ever required?
Yes, by local policy in some places. Several London boroughs require basement proposals to be accompanied by an independent audit of the geotechnical and hydrogeological work by a separately instructed qualified engineer. Build the cost and the programme time in from the start rather than discovering the requirement at validation.
How do I check a geotechnical engineer's competence?
Ask for their grade on the register of ground engineering professionals maintained by the Institution of Civil Engineers, which distinguishes advising, specialist practice and full professional responsibility, and ask for the scope that grade covers. Chartered status alone does not tell you whether the individual can take design responsibility for your category of work.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.