BSA 2022 · Technical deep-dive

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

Reviewed by Apex Insurance Brokers · 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. Design-and-build contractors placing cover for the first time can read about the broker side of design-and-build PI.

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.