Expert Witness Building Defects Claims From November 2026: How the TCC Guide 2026 and the New RICS Expert Witness Standard Change Defect and Building Safety Act Litigation

Two rulebooks have changed within five months of each other. On 1 July 2026 the Courts and Tribunals Judiciary published the fourth edition of the Technology and Construction Court Guide, the first comprehensive update since October 2022, and on 30 November 2026 the RICS professional standard Surveyors acting as expert witnesses (5th edition) takes effect [1][2][3]. Anyone preparing or defending an expert witness building defects claim in west London, whether over a leaking basement conversion in Notting Hill or fire safety defects in a modern block, now operates under both. This article explains what each changes and how a building surveyor's expert evidence should be organised from December 2026 onwards.

Key Takeaways

• The TCC Guide 2026 adds a new Section 9 on Building Safety Act 2022 proceedings, an Appendix L questionnaire for claims under sections 130 and 132, and express guidance on the use of AI in litigation [1][2].
• The TCC expects parties to give "serious consideration" to ADR and can order it; unreasonable refusal risks adverse costs even for the winning party [4].
• The Rolls Building TCC must now consider transferring claims of up to £1 million to the Central London County Court, up from £500,000 [2].
• From 30 November 2026 RICS expert witnesses must disclose AI use and financial dependence, include mandatory declarations, and never act as advocates [3].
• Expert evidence in the TCC is managed through court permission, without-prejudice expert meetings, joint statements and, where ordered, concurrent evidence.

What the TCC Guide 2026 changes for defect and building safety claims

The Guide was published on 1 July 2026, with an updated edition 4.1 following in September 2026, and applies to all TCC proceedings. Counsel and solicitors are expected to follow its "letter and spirit" [1].

Building Safety Act proceedings

Section 9 is entirely new. It records that the First-tier Tribunal decides applications for remediation orders and remediation contribution orders under sections 123 and 124 of the Building Safety Act 2022, while the High Court has jurisdiction over building liability orders and information orders under sections 130 and 132 [2]. A new questionnaire at Appendix L must accompany Building Safety Act claims brought in the TCC under sections 130 or 132 [2]. The Guide recognises that parallel TCC and tribunal proceedings may arise and that in some cases they can be heard together [4].

AI in litigation

For the first time the Guide expressly addresses artificial intelligence. Parties and their lawyers may use AI, but they remain responsible for verifying outputs, maintaining confidentiality and meeting their professional obligations [2][4].

ADR, disclosure and costs

The TCC expects parties to give "serious consideration" to ADR and can order them to engage, sometimes specifying the type. The Guide includes a draft ADR order and a Court Settlement Process in which a TCC judge acts as a confidential settlement judge. A party that unreasonably refuses ADR, or fails to cooperate with court-ordered ADR, may face adverse costs even if it wins [4]. Disclosure follows Practice Direction 57AD, and costs budgeting for Part 7 claims issued between 1 April 2025 and 30 March 2028 follows Practice Direction 51ZG1 with simplified Precedent Z budgets [5].

Value threshold

The Rolls Building TCC must now consider transferring claims of up to £1 million to the Central London County Court, double the previous £500,000 figure [2]. Many residential defect claims in Kensington and Chelsea fall within that band.

How expert evidence is managed in an expert witness building defects claim

The Guide sits on top of Part 35 of the Civil Procedure Rules. In practice, expert evidence in a TCC defect claim follows a familiar sequence.

Stage	What happens
Permission	The court must give permission under CPR Part 35, usually limited to named disciplines and issues
Reports	Each expert owes an overriding duty to the court and signs a statement of truth
Meetings	The court commonly directs without-prejudice meetings between opposing experts
Joint statement	The experts record what is agreed and what remains in dispute, with short reasons
Trial	Experts may give evidence in the usual way or concurrently ("hot-tubbing") where the judge orders it
Lower-value issues	A single joint expert is often used

Building surveyors commonly give expert evidence on the existence of defects, their cause, the appropriate remedial scope and the cost of repair as a quantum issue. The TCC's front-loaded approach means those issues should be scoped before the first case management conference, not after. A general introduction to the role is at what is an expert witness: a surveyor's guide.

What the RICS 5th edition adds from 30 November 2026

The RICS standard was published on 30 July 2026 with a four-month transition and replaces the 4th edition of 2014, as amended in 2023. It applies to all RICS members globally, with local law and tribunal rules taking precedence where they conflict [3]. Its main requirements for a surveyor expert in a defects claim are:

1. AI disclosure. Experts must disclose where AI or similar tools were used to produce evidence and explain the methodologies and analytical tools relied on [3].
2. Financial dependence. Regular reliance on, or financial dependence on, an instructing party must be disclosed: "Any such financial dependence must be disclosed in the expert's report" [3].
3. Fees. Conditional fees remain generally prohibited [3].
4. Report content. Mandatory declarations, every assumption identified, alternative conclusions where opinions depend on disputed facts or law, and competing schools of thought explained [3].
5. Instructions. Verified before acceptance and recorded, with material instructions identified in the report [3].
6. No advocacy. "An expert witness should never assume the role of an advocate" [3].

Non-compliance risks tribunal criticism, adverse costs, contempt proceedings and RICS disciplinary action [3]. Because the TCC Guide now also expects lawyers to verify AI-assisted work, a surveyor's AI disclosure under the RICS standard and the legal team's own verification duties will need to line up.

"An expert witness should never assume the role of an advocate.", RICS, Surveyors acting as expert witnesses, 5th edition [3]

Practical steps for west London claimants and defendants

Notting Hill, Holland Park and Kensington are dominated by stucco-fronted period terraces and mansion blocks that are regularly converted, extended downwards and refurbished, while the taller post-war and modern blocks fall within the Building Safety Act regime. For both types of claim the following steps reflect the two new documents.

1. Scope the expert early. Decide which disciplines are needed, which issues each will address and whether a single joint expert is proportionate, before the first case management conference.
2. Preserve the evidence. Photograph and record defects before any opening-up or repair, and keep the contractor's and designer's documents.
3. Instruct in writing. The RICS standard requires instructions to be verified and recorded; a clear written instruction protects both sides [3].
4. Ask about AI and tools. Confirm how the expert will use software, data tools or AI and how that will be disclosed [3].
5. Plan for ADR. Mediation or the Court Settlement Process should be considered before the first case management conference and documented [4].
6. Complete the Appendix L questionnaire where a Building Safety Act claim under section 130 or 132 is brought in the TCC [2].
7. Budget realistically. Expert costs and disclosure drive TCC budgets; the Guide links the two to costs management under Practice Direction 51ZG1 [5].

A Level 3 building survey carried out before a dispute crystallises often provides the baseline record that later makes an expert report credible. Where the claim concerns a recently completed home, the issues are discussed in do I need a survey on a new build. Notting Hill Surveyors' own expert work is described at expert witness surveyors London.

Frequently asked questions

Does the TCC Guide 2026 apply to claims started before July 2026?

Yes. The Guide applies to all TCC proceedings regardless of when they were issued [4].

Can an expert surveyor use AI to prepare a report?

Yes, but from 30 November 2026 the RICS standard requires the use to be disclosed and explained, and the expert remains personally responsible for every opinion [3]. The TCC Guide also expects lawyers to verify AI-assisted work [2].

What is a joint statement?

A document in which opposing experts record, after meeting, which issues are agreed and which are not, with brief reasons. The TCC routinely directs one.

Conclusion

From November 2026 an expert witness building defects claim in the TCC is governed by a Guide that front-loads expert scoping, expects ADR, addresses Building Safety Act proceedings directly and acknowledges AI, together with a RICS standard that demands transparency about tools, fees, instructions and assumptions [1][2][3][4]. The next steps for anyone contemplating or facing such a claim in west London are to preserve the evidence, instruct a chartered building surveyor in writing at the earliest stage, and plan the expert and ADR strategy before the first case management conference. This article is general information rather than legal advice; parties to a live dispute should take advice from their solicitor and an experienced expert surveyor.

References

1. Technology and Construction Court Tcc Guide 2026. judiciary.uk.
2. Tcc Guide 2026 Key Developments for Building Safety Procurement and AI. beale-law.com.
3. Surveyors Acting as Expert Witnesses. rics.org.
4. The New Tcc Guide 2026 What IT Means for Your Business. eversheds-sutherland.com.
5. Tcc Guide 2026 Building Your Case Early Has Never Mattered More. burges-salmon.com.