A foundation design report is the document that explains why a structure sits on the foundations it does. It brings together the ground model, the loads, the design method and the checks, so that a checker, a building control body or a contractor can follow the reasoning without having to rebuild it. On a UK project it is usually built on Eurocode 7, sized to the risk of the job, and issued with drawings that match it line for line.
This guide sets out what goes in, in what order, and where reports tend to go wrong. It is written for consultancies, architects and contractors who have to produce or review these reports, including when the work is shared with a remote team.
TL;DR
- A foundation design report records the ground model, design loads, assumptions, chosen foundation type, bearing and settlement checks, and construction requirements in one traceable document.
- In the UK, the geotechnical design basis is Eurocode 7 (BS EN 1997-1), applied through the UK National Annex.
- The depth of the report should match the scale and complexity of the project, and that scope should be agreed at the start.
- Weak ground investigation is the most common reason a report rests on unverified assumptions, and that is where cost and programme problems start.
- A report is only finished when its assumptions, drawings and site instructions agree, and when it has been checked by someone who did not write it.
Table of Contents
- What a foundation design report is for
- Start with the ground model
- Loads and design situations
- Choosing the foundation type
- Bearing resistance and settlement
- Durability, buildability and what the site needs to know
- Legal and procedural context in the UK
- A practical structure to follow
- Perspective: where reports slip
- Getting help with the report
- Common mistakes to catch before issue
- FAQ
- Sources
What a foundation design report is for
The report has three jobs. First, it demonstrates that the foundations can carry the building safely, with acceptable movement, for the life of the structure. Second, it records the assumptions behind that conclusion so that they can be tested if conditions change. Third, it tells the people on site what has to happen for the design to hold: excavation sequence, inspection points, groundwater control, concrete cover and so on.
It is not the same thing as a ground investigation report. The investigation report factually describes what was found in the ground. The design report interprets those findings and turns them into a foundation solution. In highway work this split is formal: the UK standard sets out a sequence of geotechnical reports that ends in the Geotechnical Design Report, with the Ground Investigation Report and the Geotechnical Design Report as separate documents. Building projects are less prescriptive, but the same logic applies: facts first, interpretation second.
The terms get mixed up in practice. A planning condition might ask for a “foundation report”, a warranty provider might ask for “foundation calculations”, and a client might simply want to know the foundations are sound. Clarify early which document is expected and who will rely on it.
Scale the report to the project
A four-storey frame on poor ground needs far more than a single-storey extension on firm clay. The highways guidance makes the point directly: the scope of geotechnical reports is tailored to the project’s scale and complexity, and report types can be combined where that is agreed at the outset. That is a sound habit on any job. Write down at kick-off what the report will cover, who reviews it, and what level of checking applies.
Start with the ground model
Everything downstream depends on the ground model, so it comes first in the report. It should state the site description, the geology expected, the strata actually found, their design parameters, and the groundwater level and its likely range.
Site investigation normally runs in a fixed order: a desk study, a walk-over survey and then direct investigation. Your report should show that each stage happened and what it contributed. A desk study that flags made ground, former trees, old mine workings or a filled pond changes what the direct investigation must look for.
Two checks are worth building into every ground model section:
- Is the investigation proportionate? Methods, layout and depths should be appropriate to the proposed development and the anticipated ground conditions. Trial pits that stop above the zone influenced by the foundations do not support a design below them.
- Are the parameters traceable? Each value used in design, such as undrained shear strength or a stiffness figure, should point back to a borehole, a test or a stated correlation, and say whether it is a cautious estimate or an average.
The risk of skipping this is practical rather than theoretical. Without adequate investigation, the design relies on unverified assumptions, which raises the chance of cost overruns and programme delays. If the report must proceed on limited data, say so plainly, list the assumptions, and say what will be confirmed on site.
Groundwater, shrink-swell and aggressive ground
Groundwater affects bearing resistance, excavation stability, buoyancy and concrete durability, so it deserves its own paragraph rather than a line in a table. Record the level found, the date of reading, and the seasonal range you have designed for. In clay soils, note the plasticity and any nearby trees or hedges, since these influence foundation depth. Where sulfates or other aggressive conditions are found, link the chemical test results to the concrete specification so the two documents cannot drift apart.
Loads and design situations
The second block of the report states what the foundations carry. List the permanent actions, variable actions and any wind or accidental cases, and say where they come from: the superstructure model, hand calculations or the architect’s layouts. Give the load at the base of each wall, column or core as characteristic values, then the factored values used for the verification.
Four points make this section easy to check:
- State the combination and partial factor set used, and the Design Approach if you are following Eurocode 7.
- Show the lightest and heaviest load cases. Uplift or eccentricity often governs, not the maximum downward load.
- Record any loads you have assumed in advance of the superstructure design, with a note to revisit them.
- Include the loading from retained soil, surcharge or neighbouring structures where relevant.
If the structure designer and the foundation designer are different people, this is where mismatches creep in. A one-page load schedule, agreed and dated by both, prevents most of them. Our note on why structural checks go beyond beam size covers the same discipline from the superstructure side.
Choosing the foundation type
The report should explain why the chosen foundation works and why the realistic alternatives were set aside. Reviewers learn a lot from this paragraph. A short comparison, even in a few lines, shows that the choice was made and not simply inherited from the previous job.
| Option | Typically considered when | Main constraints to record |
|---|---|---|
| Strip or pad footings | Competent ground at modest depth, light to moderate loads | Depth to good bearing, groundwater, trees, nearby services |
| Raft | Variable or weak near-surface ground, need to spread load and limit differential movement | Edge detailing, stiffness, interaction with the ground |
| Piles with ground beams or a cap | Weak or compressible ground near the surface, heavy or concentrated loads | Access for rigs, vibration, pile testing, reinforcement and installation sequence |
| Pier and beam | Variable depth to bearing ground, restricted access | Excavation stability, spacing, beam design |
Construction constraints belong in this section too. Site access, adjacent structures, working near boundaries, contamination, and the ability to dewater all narrow the options. Write them down, because they are often what actually decides the answer.
For the specific checks on shallow foundations, our guide on shallow foundation bearing capacity, checks and UK practice goes further than there is space for here.
Bearing resistance and settlement
This is the core of the calculation section. Two things have to be demonstrated: that the ground will not fail under the design loads, and that movement stays within what the structure can tolerate.
Bearing resistance. Show the method, the parameters, the foundation dimensions, the design resistance and the utilisation ratio. Treat drained and undrained conditions separately where both could govern. Eurocode 7 sets out general rules for the geotechnical aspects of building and civil-engineering design, and NHBC guidance states that UK foundation design should be informed by Eurocode 7 as the framework for geotechnical calculations and safety verification. Cite the clauses and the National Annex values you used, not just the standard’s number.
Settlement. State the estimated total and differential settlement, the method, the ground stiffness assumed, and the limit you are checking against. For clays, say whether consolidation is included and over what time. Link the acceptable movement to the structure: a masonry building with brittle finishes tolerates less than a steel portal.
Sensitivity. A good report shows what happens if the groundwater is higher, the stiffness is lower or the loads rise. One short table of three or four sensitivity cases will often be the most valuable page in the document.
Calculation presentation
Presentation matters more than people admit. Put the inputs at the top of each calculation, number the clauses, show units throughout, and finish with a clear pass or fail. A checker should be able to read one sheet without flicking to another to find a dimension. We have written about how this plays out in a calculation and drawing review workflow.
Durability, buildability and what the site needs to know
A foundation that passes every calculation can still fail in construction. The last technical section of the report turns the design into instructions:
- Excavation and formation: how the formation is to be inspected, by whom, and what to do if soft spots appear.
- Groundwater control and excavation support during the works.
- Concrete specification, cover and any protection against aggressive ground.
- Sequence constraints, for example where piles are installed relative to ground beams.
- Monitoring, if movement of the structure or its neighbours must be tracked.
NHBC’s requirements state that critical construction sequences, such as pile reinforcement and excavation stability, must be communicated to site supervisors and specialist subcontractors. Put those items on the drawings and in the report, not only in a covering email.
The same highways guidance for design reports expects the supervision, monitoring and future-maintenance requirements to be set out alongside the design justification. For buildings, a short maintenance and monitoring note does the same job: trees to be kept clear, drains to be kept sound, and any movement markers to be read.
Legal and procedural context in the UK
Under the Construction (Design and Management) Regulations 2015, clients have a duty to provide pre-construction information about ground conditions to designers and contractors. In practice that means your ground investigation findings, and the foundation report’s list of residual risks, should reach the principal designer and the contractor in good time. Designers also have to consider how their design affects those building it, which is another reason the construction section above is not optional.
On highways schemes the process is stricter. Reports go to the Overseeing Organisation with a signed certificate, and category 3 work is independently checked unless that is waived. Building work is not bound by that process, but the principle transfers well: the person who checks the design should not be the person who produced it. A Geotechnical Feedback Report, recorded in some sectors such as highways, captures what was actually found during construction and any problems resolved on site. Even where it is not required, a one-page feedback note is cheap insurance for the next project on the same ground.
A practical structure to follow
If you need a skeleton, this order works for most building projects:
- Summary and conclusions, including the recommended foundation type and key limits.
- Scope, brief, and documents relied on.
- Site description and ground model, with groundwater.
- Design basis: standards, National Annex, partial factors, design life.
- Loads and load combinations.
- Foundation options and selection.
- Bearing resistance, settlement and stability calculations.
- Durability, construction requirements and monitoring.
- Residual risks, assumptions to verify on site and limits of reliance.
- Appendices: calculations, drawings, investigation data, checking certificate.
Put the conclusion first. Readers at planning, building control or the contractor’s office will rarely get past page two, so the foundation type, bearing pressure and any critical conditions must be there.
Perspective: where reports slip
We see the same problems over and over on overflow work, and they are rarely about the maths. The calculation is correct, but the load schedule was out of date, the groundwater assumption in the report differs from the one on the drawing, or the ground investigation stopped a metre short of where the footings need it. Each is a coordination fault, not a design fault.
Our approach is to treat the report as a controlled document from the first day. We agree the scope and the checking route at kick-off, keep one load schedule, and issue calculations in a form a reviewer can follow without a call. Our engineers work inside your workflow and to UK standards and Eurocodes, and the client relationship stays with you. When we embed with a consultancy, the best sign that it is working is that the reviewer’s comments are about judgement, not about missing information.
If you take one habit from this article, make it this: every assumption in the report should have a name, an owner and a way of being confirmed on site.
— Mohammed
Getting help with the report
If your team is stretched, foundation calculations and reports are well suited to remote support because the inputs are clear and the outputs are reviewable. Our structural engineering team prepares structural reports and calculation packages, and our remote engineering support embeds engineers in your process, with kick-off within 48 hours, NDA protection and no recruitment fees. See a worked example in our structural calculation support case for a UK consultancy. If drainage is part of the same planning submission, our guide to the drainage strategy report shows how to keep the two documents consistent.
Common mistakes to catch before issue
- Out-of-date loads. Check the load schedule date against the latest superstructure revision.
- Unstated groundwater. Every report should name the level and where it came from.
- Parameters without a source. If a value cannot be traced to a test or a stated correlation, flag it as an assumption.
- No alternative considered. One sentence on why the other options were rejected saves a review round.
- Drawings that disagree with the report. Section depths, levels and reinforcement should match exactly.
- Reliance left vague. State who may rely on the report and for what purpose. Third-party use usually needs an agreement, and significant changes to the site or the scheme call for a review.
- No handover to site. The inspection points and sequence constraints need to be on the drawings, not just in the report.
A useful final test: hand the report to someone who has not seen the project and ask them to explain the foundation choice in two minutes. If they cannot, the summary needs work.
FAQ
What is the difference between a ground investigation report and a foundation design report?
The ground investigation report records factual findings: boreholes, trial pits, laboratory tests and groundwater readings. The foundation design report interprets that information, chooses a foundation, and demonstrates by calculation that it is safe and serviceable. The two are separate documents, and the design report should reference the investigation data it relies on.
Which standard should a UK foundation design report follow?
The geotechnical design basis is Eurocode 7, BS EN 1997-1, used with its UK National Annex. The structural design of the foundation element itself follows the relevant Eurocode for the material. State in the report which parts and which National Annex values you used.
Do I always need a ground investigation before designing foundations?
The level of investigation should suit the project and the anticipated ground. Without it, the design rests on unverified assumptions, which raises the risk of cost and programme problems. For small works in well-known ground, a desk study and walk-over may be enough to proceed on stated assumptions, but a structural engineer should agree that.
Who should check the report?
Someone independent of the author, with the competence to judge the ground model and the calculations. Highway work requires this formally for higher-risk categories, and the same principle is sensible on building projects. We can prepare the calculations and package so your reviewer receives a document that is easy to check.
Sources
- Eurocode 7: Geotechnical design, Part 1 (BS EN 1997-1:2004)
- Managing geotechnical risk (Standards for Highways)
- Site investigation for foundations (Concrete Society)
- Soil and Ground Investigation Report (Construction Suite)
- Efficient design of piled foundations for low-rise housing (NHBC)
- NHBC Standards, Chapter 4.4: Raft, pile, pier and beam foundations
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