Fire safety expert witness (Part 35): when you need one and what they do

When fire safety becomes a dispute

Fire safety questions are at the centre of many building disputes:

• Defective construction – combustible cladding, missing cavity barriers, inadequate fire-stopping or compartmentation
• Professional negligence – fire strategies, FRAEWs, EWS1 forms or fire risk assessments said to fall below a reasonable standard
• Remediation costs – claims against developers, contractors and designers, and applications for remediation contribution orders – see cladding remediation funding
• Insurance claims after a fire – cause, spread and whether the building performed as it should
• Landlord and tenant – whether fire safety works were necessary and their cost recoverable

What a fire safety expert witness does under Part 35

In civil litigation in England and Wales, expert evidence is governed by Part 35 of the Civil Procedure Rules and its Practice Direction. Key principles:

• The duty to the court. An expert's duty is to help the court on matters within their expertise. That duty overrides any obligation to the person instructing or paying them.
• Permission. No party can rely on expert evidence without the court's permission, and the court restricts it to what's reasonably required.
• Single joint experts. The court can direct that one expert is instructed jointly by both parties.
• Written questions. Parties can put written questions to the other side's expert to clarify their report.
• Discussions and joint statements. Experts may be directed to discuss the issues and produce a statement of what they agree and disagree on.

What the report must contain

Practice Direction 35 requires an expert report to include, among other things:

• The expert's qualifications and relevant experience
• The material relied on, including instructions and documents
• Who carried out any tests or inspections
• Where there's a range of opinion, a summary of it and the reasons for the expert's own view
• A summary of conclusions
• A statement that the expert understands their duty to the court, and a statement of truth

Tribunals and arbitrations have their own rules, but the same principles of independence and objectivity apply.

Advisory experts vs Part 35 experts

Before proceedings, many clients instruct an advisory expert to give a confidential view on the technical merits – whether a fire strategy was deficient, whether the cladding needed replacing, whether costs are reasonable. That can save a great deal of money on claims that won't succeed. If the matter proceeds, the same or a different expert may then be instructed under Part 35.

Choosing a fire safety expert

• Relevant, current experience of the specific issue – an FRAEW dispute needs someone who carries out FRAEWs
• Independence – no conflicts with any party, contractor or previous report
• Clear writing – the court must be able to follow the reasoning
• Experience giving evidence, or the training to do so
• Capacity to meet the court timetable

Typical questions a fire safety expert is asked

• Did the external wall construction comply with the Building Regulations and guidance at the time?
• Was the fire-stopping or compartmentation installed to a reasonable standard?
• Did a fire strategy, FRAEW or fire risk assessment meet the standard expected of a reasonably competent professional?
• Was the remediation that was carried out necessary and proportionate, and were the costs reasonable?
• How did a fire start and spread, and did the building perform as it should have?
• What would a compliant design have looked like, and what would it have cost?

Our peer review and expert witness service provides independent fire safety experts for advisory and Part 35 work. See also when to get a report peer reviewed.

Sources

• Ministry of Justice – Civil Procedure Rules Part 35: experts and assessors
• Ministry of Justice – Practice Direction 35: experts and assessors

This guide is general information based on the law and guidance in England as at 8 November 2026. It isn't legal advice – for advice on a specific building, get in touch.