CPR Part 35 Explained: When Should You Instruct a Surveyor as an Expert Witness?
posted 29th June 2026
Property disputes often require more than technical knowledge—they require independent expert evidence that can withstand legal scrutiny.
At Tayross Associates Ltd, we regularly advise clients involved in construction, boundary, dilapidation, defect and professional negligence disputes. One of the most common questions we are asked is, "When does a surveyor become an expert witness rather than simply acting as an adviser?"
The answer lies in CPR Part 35 of the Civil Procedure Rules.
What is CPR Part 35?
CPR Part 35 governs the use of expert evidence in civil proceedings in England and Wales. It sets out the responsibilities of professionals instructed to provide expert opinions to the court.
The overriding principle is clear:
An expert witness's duty is to the court—not to the client, solicitor or party paying for the report.
This duty requires complete independence, impartiality and objectivity. An expert witness is not an advocate for either side but an independent professional whose role is to assist the court on matters within their expertise.
Advisor or Expert Witness – What's the Difference?
Surveyors often fulfil both roles, but they are fundamentally different.
Acting as a Surveying Advisor
When acting as an adviser, we work exclusively in our client's interests.
This may include:
Assessing defects or property condition.
Advising on liability and risk.
Assisting with negotiations.
Providing technical opinions to help clients make informed decisions.
Our duty in this role is to our client.
Acting as an Expert Witness
When instructed as an expert witness, our role changes.
Our overriding duty becomes one of independence. We must provide an honest and unbiased opinion based solely on the evidence, regardless of whether it supports or undermines the case of the party who instructed us.
Every opinion must be supported by evidence, explained clearly, and remain within the limits of our professional expertise.
When Does a Surveyor Become an Expert Witness?
A surveyor typically becomes an expert witness when they are:
Instructed by solicitors in connection with existing or anticipated litigation.
Asked to prepare an expert report for use in court proceedings.
Appointed jointly by the parties as a Single Joint Expert.
Directed by the court to provide independent expert evidence.
At this stage, any report must comply with CPR Part 35 and include the appropriate declarations confirming the expert understands their duty to the court.
Can an Expert Report Be Prepared Before Court Proceedings?
Yes. In fact, this is often the most sensible approach.
Many expert reports are commissioned before proceedings are issued. Early expert advice helps clients understand the strengths and weaknesses of their position and can often encourage settlement without the need for costly litigation.
Pre-action expert reports are commonly obtained:
Before a Letter of Claim is sent.
During pre-action negotiations.
To assess defects or causation.
To quantify losses.
To support Alternative Dispute Resolution (ADR).
If litigation later follows, the report can often be relied upon, provided it has been prepared in accordance with CPR Part 35.
Why Early Expert Advice Matters
Obtaining expert advice at an early stage can save significant time and expense.
An independent expert opinion can:
Clarify the technical issues.
Identify strengths and weaknesses in a case.
Assist solicitors in advising their clients.
Encourage early settlement.
Reduce the costs of litigation.
Whether a matter proceeds to court or is resolved through negotiation, robust expert evidence provides clarity and confidence.
How We Can Help
At Tayross Associates Ltd, we provide both independent expert witness services and technical surveying advice across a wide range of property and construction disputes.
Our reports are prepared with professionalism, independence and attention to detail, ensuring they meet the standards expected by the courts where required.
If you require advice on a property dispute or need to instruct an expert witness, our experienced surveyors are available to discuss your requirements and recommend the most appropriate course of action.
Need expert surveying advice?
Contact Tayross Associates Ltd to discuss your matter with one of our experienced surveyors.
