What an Expert Witness Actually Does, and Why the Distinction Matters
Most people involved in a building or structural dispute reach the same point eventually: they have a problem, their solicitor needs technical evidence, and they are told they require an expert. What that means in practice, and what it involves, is less well understood, particularly for homeowners and smaller businesses who have not been through the process before.
ABI (Association of British Insurers) data shows that UK property insurance claims totalled £4.1 billion in the first nine months of 2024 alone, the highest figure in any equivalent period on record. A significant proportion of those claims involve disputes over cause, liability, or the extent of damage, situations where an independent technical assessment becomes the determining factor in whether a claim is accepted, settled, or contested further.
Buildings insurance complaints reached a 10-year high in 2024, with 2,001 cases brought to the Financial Ombudsman in a single quarter, representing a 13% year-on-year increase. Many of those complaints relate to claims that were delayed, undervalued, or declined; outcomes that a properly instructed independent expert can directly address.
What CPR Part 35 Means for Your Case
In civil proceedings in England and Wales, expert witness evidence is governed by Part 35 of the Civil Procedure Rules (CPR). Under CPR Part 35, an expert’s overriding duty is to the court, not to the party who instructs or pays them. This is not a formality. It is the legal foundation on which the credibility of expert evidence rests, and it is the reason courts place weight on it.
An expert report must be thorough, clear, and CPR-compliant, concluding with a signed statement of truth confirming that the expert understands and accepts their overriding duty to the court. A report that does not meet these requirements can be excluded from proceedings, an outcome that significantly weakens the instructing party’s position and may result in costs penalties.
At Istidam Consulting, all expert reports are prepared to full CPR Part 35 compliance. Our engineers remain impartial at all times, with findings based solely on site evidence, technical analysis, and applicable standards, independent of the position of whoever instructs us.
For Homeowners: The Situations Where You Are Likely to Need This Service
Building disputes affecting private homeowners typically arise in one of several ways. A contractor carries out structural work that later proves defective. An extension or conversion develops cracking that was not present before. An insurance claim for subsidence or structural damage is disputed or declined. A property purchase completes, and structural defects emerge that were not disclosed or identified in the pre-purchase survey.
Under the Limitation Act 1980, builders are typically liable for defects for six years from completion of the work. That window is longer than most homeowners assume, and identifying the cause and attributing liability within it requires independent technical evidence, not a contractor’s own opinion on their work, and not an insurer’s loss adjuster acting in the insurer’s interest.
Subsidence pay-outs by UK insurers reached £66 million in Q3 2024, up 61% on the same quarter the previous year. In many of those cases, the disputed questions are not whether subsidence has occurred, but what caused it, who is responsible, and whether the remediation proposed is proportionate. Those are technical engineering questions that require an independent structural engineering expert witness to resolve.
For homeowners, an Istidam expert witness instruction typically covers: site investigation and measurement, assessment of crack patterns and building movement, review of construction documentation and planning records, analysis of third-party reports including insurers’ assessments, and preparation of a CPR Part 35-compliant expert report setting out findings, causation, and, where relevant, remediation scope.
For Commercial Clients, Solicitors, and Insurers: The Technical Scope
In commercial disputes and litigation, the range of structural and civil engineering issues that require expert input is broad. The matters we are instructed on span the full spectrum of civil and structural engineering: reinforced concrete deterioration and specification disputes, steel corrosion assessments, bridge and highway defect investigations, pavement and hardstanding failures, basement waterproofing failures, and forensic engineering investigations following structural failure or collapse.
The volume of high-value construction professional negligence claims in the UK has been rising, with a perceived shortage of available and suitably qualified technical experts already causing delays in dispute resolution. Instructing a Chartered Engineer with direct relevant experience in the specific area of dispute, rather than a generalist who may lack the technical depth to withstand cross-examination, reduces the likelihood of the evidence being challenged on qualification grounds and produces a report that courts and tribunals are more likely to give weight to.
For solicitors managing litigation, Istidam engineers can be instructed as a party-appointed expert or as a single joint expert under CPR 35.7. Where the court directs that experts from both parties discuss the case and prepare a joint statement, our engineers engage in that process professionally and within the procedural timescales required. We are also instructed for pre-litigation advisory work, where early technical clarity can inform settlement negotiations and avoid the cost of proceedings.
For insurance companies and loss adjusters, our forensic engineering investigations provide independent causation assessments on structural and civil engineering claims, including subsidence, building defects, drainage failures, and construction damage, that are defensible at arbitration, mediation, or trial.
Instructing Istidam Consulting
If you are a homeowner facing a building defect dispute, a solicitor requiring a CPR Part 35-compliant expert report in a civil or structural engineering matter, or an insurer or business needing independent technical evidence, contact Istidam Consulting to discuss your instruction. Our engineers will confirm scope, timescales, and fees at the outset. Where an instruction falls outside our expertise, we will say so.
