BSA 2022 · Technical deep-dive

BSA 2022 s.135 Principal Designer / RBCA — deep-dive

Reviewed by Matthew Bartlett, Director, Apex Insurance Brokers Limited · Published 15 July 2026

The Building Safety Act 2022 has redefined liability for design professionals working on higher-risk buildings. Section 135 extends limitation to 30 years retrospective (for pre-June 2022 work) and 15 years prospective (for post-June 2022 work) on defective premises claims involving HRBs. The Principal Designer role under the RBCA regime carries specific statutory duties. This page unpacks both.

Section 135 in detail

What section 135 does

Amends section 1 of the Defective Premises Act 1972. Extends limitation for defective premises claims from six years to 30 years retrospective / 15 years prospective on higher-risk buildings.

Defective premises framework

Section 1 DPA 1972 imposes duty on those undertaking work in connection with a dwelling to see it's done in a workmanlike or professional manner, with proper materials, so the dwelling is fit for habitation. Section 2 excludes claims once a dwelling is deemed fit for habitation.

Higher-risk buildings

As defined by the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023: buildings 18 metres or 7+ storeys AND containing 2+ residential units. Captures a wide range of urban residential blocks.

Retrospective effect

Work completed before 28 June 2022 has 30-year limitation running from cause of action accrual. Practical effect: designs completed in 2010 remain exposed until 2040.

Prospective effect

Work completed after 28 June 2022 has 15-year limitation. Combined with the statutory Principal Designer duties, this creates a distinct liability profile.

Principal Designer statutory duties (RBCA regime)

The BSA introduces the Relevant Building Contract Act regime for higher-risk buildings. Principal Designer becomes a statutory duty-holder role:

Design safety competence. PD must be competent in fire safety and structural safety of the specific building type.
Design safety file. Mandatory maintenance of a comprehensive design safety file passed forward to the building owner.
Gateway participation. PD participates in Building Safety Regulator's Gateway 2 and Gateway 3 sign-off processes.
Coordination with Principal Contractor. Statutory duty to coordinate design and construction phase safety.
Notification obligations. Certain events trigger notification to BSR.

PI implications for architects and engineers

30-year exposure on HRB work. Requires extended run-off cover for retirement.
PD-specific coverage. Standard architect PI wordings may not explicitly cover the new statutory duties.
Cover-limit review. Pre-BSA cover of £250k or £500k typically inadequate for practices with material HRB work.
Documentation discipline. Design safety file maintenance is now a statutory obligation with PI implications.

Frequently asked

What's a higher-risk building?

Buildings 18m+ or 7+ storeys with 2+ residential units. Definition from HRB Regs 2023.

Does section 135 apply to all my past work?

For HRB work: yes, retrospective to 30 years. For non-HRB work: standard six-year limitation still applies.

Do I need PD-specific PI wording?

Yes if you act as Principal Designer on HRB projects. Standard architect PI may not explicitly cover the statutory duties.

How much extended run-off do I need?

For practices with HRB work: 12-30 years depending on file. Standard six years leaves material gap.