Cladding and EWS1 Disputes: Expert Witness Evidence on External Walls

A cladding expert witness is a chartered surveyor or fire engineer who gives independent, court-compliant evidence on what is actually in a building’s external walls, whether that construction complied with the Building Regulations in force when it was built, and what it will reasonably cost to put right. Since the Grenfell Tower fire, cladding and EWS1 disputes have become one of the busiest areas of property litigation in England and Wales, and almost all of them turn on expert evidence. This guide explains which forums hear them, what the report must establish and what it costs.

Why cladding and EWS1 disputes need expert evidence

The EWS1 form is a one-page valuation document, not a legal finding. A B2 rating tells a lender that combustible materials are present and remediation is required, but it does not say who is responsible, whether the original construction breached the Building Regulations, or what the proportionate fix is. A court or tribunal cannot answer those questions on the strength of the form alone.

The external wall system includes the outer panels, the insulation behind them, cavity barriers, fire stopping at compartment lines and the fixings holding it all together. Deciding whether a wall is dangerous, whether a Fire Risk Appraisal of External Walls (FRAEW) under PAS 9980 was carried out competently, and whether full replacement or a lesser intervention is justified calls for opinion evidence that a lay witness cannot give. Under CPR Part 35 that opinion must come from an independent expert with a duty to the court, not from a party’s own consultant.

Where cladding disputes are heard

Most cladding claims fall into four categories, and the forum shapes the expert’s task.

• Remediation orders at the First-tier Tribunal (Property Chamber). Under section 123 of the Building Safety Act 2022, leaseholders, regulators and others can apply for an order requiring the landlord to remedy “relevant defects” in a relevant building (broadly, at least 11 metres or five storeys). The tribunal needs expert evidence on whether a defect exists, whether it creates a building safety risk and what works are needed.
• Remediation contribution orders and claims against developers. Section 124 of the 2022 Act allows the tribunal to order developers, landlords and associated companies to contribute to remediation costs. Building owners also sue the original developer, contractor, cladding subcontractor, architect and fire engineer in the Technology and Construction Court.
• Defective Premises Act 1972 claims. The 2022 Act extended the limitation period for claims under section 1 of the 1972 Act to 30 years for dwellings completed before 28 June 2022, reviving claims on blocks built in the 1990s and 2000s. The expert must show the dwelling was not fit for habitation when completed.
• Professional negligence and transaction claims. Buyers who relied on a survey, valuation or EWS1 assessment that missed a cladding problem may claim against the professional. A surveyor negligence expert witness then assesses whether that professional met the standard of a reasonably competent practitioner at the time.

Disputes under a live building contract may go to construction adjudication instead; see the guide to expert evidence in adjudication.

What a cladding expert witness report must establish

Whatever the forum, the report has to answer four core questions in a form that satisfies Practice Direction 35 and the RICS practice statement Surveyors acting as expert witnesses.

What is in the wall. Desk evidence (as-built drawings, specifications, Building Control records) is rarely enough; the expert will normally need intrusive opening-up at representative locations to confirm the panel type, the insulation product, the cavity barriers and the fixing method.

Whether it complied at the time. The benchmark is the Building Regulations and Approved Document B as they stood when the work was approved, not today’s standards. The 2018 ban on combustible materials in the external walls of relevant buildings over 18 metres applies only to work after it came into force, so the expert has to be precise about dates, the guidance edition relied on and whether a fire-engineered alternative route was used.

Whether the EWS1 or FRAEW was competently done. Where the dispute concerns an assessment rather than the original construction, the expert reviews the methodology against PAS 9980, the assessor’s qualifications and the information available to them, and says whether a reasonably competent assessor could have reached the same rating.

What the proportionate remedy is and what it costs. Courts and tribunals are alert to over-specification, so the expert should set out costed options, from full recladding to targeted replacement of insulation or cavity barriers, and explain why the recommended scope is reasonable. Where the claim is for diminution in value rather than repair, a valuation expert witness may be instructed alongside the building surveyor.

The report must also give the expert’s qualifications, state the substance of all material instructions, identify the facts and assumptions relied on and carry the PD35 statement of truth. The broader framework is explained in the guide to expert evidence in building defects claims.

Which expert discipline do you need?

Cladding disputes often need more than one expert, and instructing the wrong discipline is an expensive mistake. A chartered building surveyor is usually the right lead expert on what was built, whether it matched the specification and drawings, what defects are present and what remediation will cost. A chartered fire engineer is needed where the fire-engineering analysis itself is contested, such as the acceptability of a fire-engineered design or the assumptions behind a PAS 9980 appraisal. A RICS Registered Valuer deals with loss of value and the effect of a B2 rating on saleability. In multi-party TCC litigation each party commonly has permission for experts in two or three disciplines.

The professionals who wrote the existing FRAEW or EWS1 are rarely suitable as independent experts, because they would be defending their own conclusions. The guide to when to instruct an expert witness for construction defects covers the early-advice stage.

How much does a cladding expert witness cost?

Cladding reports sit towards the upper end of the published ranges because of the intrusive investigation, document volume and number of parties. For the panel’s chartered surveyors, hourly rates are typically £150–£300. A CPR Part 35 report on a straightforward matter, such as a single-block remediation order application or a negligence claim about one flat, generally falls within £5,000–£15,000. Multi-block or multi-party TCC claims that need extensive opening-up, costed options and several rounds of joint statements can reach £20,000–£50,000 or more. Attendance at trial or a tribunal hearing is usually charged at £1,000–£2,000 per day. Opening-up works, access equipment and laboratory testing of samples are separate costs.

In the First-tier Tribunal each side normally bears its own costs, so an applicant should budget for the whole expert fee. In the TCC the losing party usually pays a proportion of the winner’s reasonable expert fees, and the court can limit recoverable fees under CPR 35.4(4). Fixed fees are quoted wherever the scope is clear, and single joint expert appointments are accepted where the court or tribunal directs one.

Cladding expert witness services from Survey Merchant

Survey Merchant provides RICS chartered surveyors as construction expert witnesses in cladding, EWS1 and external wall remediation disputes, drawn from a national panel of 2,400+ surveyors working to CPR Part 35 and the RICS practice statement. The panel’s experts prepare reports for leaseholders, management companies, freeholders, developers, insurers and their solicitors, act in First-tier Tribunal remediation order applications and TCC proceedings, and are paired with valuation experts where diminution in value is in issue. Before litigation, a specific defect report on the external wall can establish the facts, and leasehold advice is available to flat owners caught between a B2 rating and a stalled sale. To discuss a cladding dispute, contact Survey Merchant or call 0204 579 8270, and the right expert will be matched to the issues in dispute.