Architects and BSA 2022 s.135: the 30-year retrospective limitation window

~5 min read

Reviewed by Matthew Bartlett, Director · Last reviewed 2026-07-06

The Grenfell Tower fire of 14 June 2017 exposed structural failings in the UK building safety regime and set in motion a decade of legislative and regulatory reform. The Building Safety Act 2022 was the centrepiece. For architects and other design professionals, the single most consequential provision is section 135, which amended section 1 of the Defective Premises Act 1972 to extend the limitation period for claims relating to defective residential dwellings to 30 years retrospectively and 15 years prospectively. That change has reshaped the architects' PII market. Insurers repriced. Some withdrew. Firms with material historical residential exposure have had to rethink their run-off planning, their current cover, and — in some cases — the future shape of their practice. This entry sets out what section 135 did, why the market responded as it did, and where the market stands in 2026.

What section 135 did

Section 1 of the Defective Premises Act 1972 imposes a duty on those who take on work in connection with the provision of dwellings to see the work is done in a workmanlike or professional manner. Architects, contractors, subcontractors and other design and construction professionals fall within its scope where their work relates to a "dwelling". Before the BSA, that duty was subject to a six-year limitation period under section 1(5) of the DPA as read with the Limitation Act 1980. Section 135 of the BSA amended section 1(5) of the DPA to extend the limitation period. For defective dwellings completed before the BSA commenced (28 June 2022), the limitation period is now 30 years — retrospective. For dwellings completed after the BSA commenced, the limitation period is 15 years — prospective. Both changes are in force.

Which architects are exposed

The exposure attaches to any architect whose work fell within DPA section 1 — the "provision of dwellings" test. That captures architects who designed dwellings, who acted as contract administrators on dwelling projects, who provided lead consultant services on residential schemes, and who certified under building regulations for dwellings. It does not attach to architectural work on purely commercial property unless that work also touched residential elements of a mixed-use scheme. A commercial fit-out architect with no residential work in the last 30 years is not exposed under section 135. An architect with 20 years of predominantly residential work is very much exposed.

The retrospective element

The retrospective 30-year limitation is the harder of the two changes to price. A residential dwelling completed in 2000 that a firm's founding partner designed as a young architect is now, in principle, capable of being the subject of a DPA claim until 2030. A residential dwelling completed in 2010 is exposed until 2040. Files that everyone had assumed were closed under the previous six-year limitation are now potentially live. Firms with heavy historical residential books have found themselves reassessing exposure they had not thought about for years, and insurers have responded by asking more searching proposal-form questions about historical residential work.

The prospective element

The 15-year prospective limitation applies from 28 June 2022 forward. It is easier for insurers to price because it operates prospectively — the underwriting mathematics can factor in a 15-year claim tail rather than the six-year tail that applied before. Architects taking on new residential work post-BSA should understand that their PII exposure on that work extends 15 years from practical completion, not six.

The market response

The architects' PII market repriced through 2022 and 2023 in response. Several insurers reduced their appetite for residential-heavy architectural books; a small number exited the market altogether. Premium rates rose materially for firms with visible residential exposure — reports of 30-50% year-on-year increases were common in the immediate aftermath of the BSA. By 2024-2025 the market had stabilised but rates for residential-heavy architectural work sit meaningfully above their pre-BSA level. The 2026 market feels disciplined but soft for clean commercial practices and disciplined but firm for residential-heavy practices.

What insurers are asking at proposal

Proposal forms for architects' PII now ask, in effect, four things about historical residential work. First, what proportion of fee income over the last 30 years came from residential dwelling work? Second, what was the largest single residential project by construction value? Third, are historical files accessible and reviewable, and what document retention policy has the firm operated? Fourth, has the firm reviewed its historical residential file records for defect exposure since the BSA commenced? Firms unable to answer these questions coherently at proposal face either a decline or a materially higher rate.

Run-off implications

The BSA change has moved the run-off decision from a routine six-year placement to a substantive risk-management question. Six years is the market baseline for architects' run-off, matching the historical DPA limitation and the general Limitation Act limitation for contract claims. For a firm with any material historical residential exposure, six years is now demonstrably inadequate. A file from 2020 that becomes the subject of a claim in 2032 sits outside a six-year run-off period. Brokers are increasingly recommending extended run-off of 15, 20 or 30 years for architects winding down with residential back-books.

Practical points for continuing practice

For firms continuing in practice, three practical points matter. First, current cover should be sized against the extended prospective exposure on new residential work — a 15-year claim tail changes the accumulation exposure across the book. Second, historical file records should be reviewed and, where possible, digitised. Files that were archived to physical storage in 2005 need to be accessible if a claim surfaces in 2028. Third, the practice's future residential appetite should be a considered decision rather than a default — some firms have deliberately reduced their residential exposure post-BSA because the risk-adjusted returns are less attractive; that is a defensible commercial choice, not an admission of failure.

Worked example

Illustrative only. A six-partner architectural practice with a mixed commercial and residential book. Fee income £1.8m: 60% commercial, 40% residential. Historical residential work stretches back 25 years, including a significant volume of small residential extensions and conversions from 2000 to 2015. Under the BSA retrospective extension, the pre-BSA residential back-book carries claim exposure to 2030-2045. Broker recommendation: current PII limit £5m primary + £5m top-up (£10m tower), with an explicit high-risk building endorsement to cover any residential work above 18 metres; historical file review completed with digitisation of pre-2010 records; 20-year run-off costed as a contingency figure so partners understand the exposure attached to any decision to cease within the next decade. Renewal completed on this basis with an insurer whose appetite for the residential exposure is well-established.