Replacing Windows in a High-Rise Flat: Why the FENSA Route Doesn't Work, and What 2026 Might Change

By Alicja Salter, Building Surveyor and BSR compliance consultant (MSc Building Surveying) · Last reviewed 23 October 2026

If you own a flat in a building of 18 metres or more, you probably cannot replace your windows the way your friends in a terraced house can. That surprises almost everyone I speak to.

The usual assumption is simple: hire a FENSA-registered installer, they self-certify the work, and a compliance certificate arrives a few weeks later. In a higher-risk building (HRB), that route is effectively closed. The result is delays, unexpected applications to the Building Safety Regulator (BSR), and sometimes work started without the approval it legally needed.

This article sets out where things stand in October 2026, why the gap exists, and what the government's 2026 reforms might change.

What the rules say on paper

Since October 2023, BSR has been the building control authority for HRBs in England. For existing buildings, that means buildings of at least 18 metres or 7 storeys with two or more residential units.

GOV.UK guidance says you need BSR building control approval before starting building work to an existing HRB. There are three exceptions: exempt work, work done under a competent person scheme (CPS), and emergency repairs.

Replacing a window counts as building work under the Building Regulations, but it is also classic CPS work. In theory, then, a CPS installer could self-certify a window replacement in an HRB flat without going to BSR at all.

Why it doesn't work in practice

The schemes themselves have stepped back. FENSA has announced that replacement windows, doors and rooflights in buildings over 18 metres can no longer be self-certified through the scheme, and says the other glazing schemes have agreed the same approach. Its reasoning is that taller buildings carry specific fire risks that need independent inspection.

The effect is a gap between regulation and reality. The CPS exception exists in law, but the glazing schemes have said they won't use it in buildings of this height. In practice, a window replacement in a high-rise flat goes to BSR for building control approval like any other HRB work.

The gap has been raised officially. In July 2025, a Freedom of Information request asked HSE which schemes BSR recognises for window replacement in HRBs. HSE replied that the legislation decides which schemes can certify, and that BSR held no correspondence with them. The requester then reported that FENSA, Certass and Assure had each confirmed they do not certify work in HRBs.

I saw this first-hand on a recent project at a landmark residential building in central London. The windows in one flat were in very poor condition, and leaving them through another winter was a genuine safety risk. The owner tried to find a FENSA-registered installer to replace them, but none of the contractors approached would take the job on, because they could not self-certify work in a building of this height. The result was urgent, necessary work stuck in a gap that the competent person scheme system was supposed to fill. Nor did the emergency repairs exception offer an easy way out: as the rules stand, it covers urgent repairs rather than replacements.

What 2026 might change

The government has accepted that parts of the HRB regime are disproportionate for small works, and 2026 brought several signals of change.

Category A and B. Work to existing HRBs is split into Category A and Category B. Both need BSR building control approval, but Category B applications carry lighter information requirements. In March 2026 the government consulted on redrawing that line. Its response on 9 July said it is minded to move most work inside residential units into Category B. No final decision has been made.
Windows specifically. The consultation set out two options. Option 1 takes work inside individual flats out of Category A; Option 2 does the same for small-scale works in communal areas. The small-scale test (roughly a team of three or fewer, or up to five working days, with no impact on active fire safety systems, load-bearing walls or external walls) expressly carves building work to windows out of the external wall restriction. That is an encouraging signal for window replacements, but the final rules have not yet confirmed how windows in flats will be treated.
A role for competent person schemes. The same consultation asked whether new competent person schemes could cover more Category B work. A separate consultation, which closed on 3 September 2026, proposed widening "emergency repairs" to "emergency works" or creating a new "critical works" route, and asked whether some emergency works could be self-certified.
BSR's own direction. Since January 2026, BSR has been a standalone body under MHCLG. Its 2026–27 plan includes a fundamental review of guidance to the building regulations.

One more date matters for anyone specifying windows: the 2026 edition of Approved Document L for dwellings applies to HRB work from 24 September 2027, six months after other buildings.

What to do now

Until the reforms are final, plan as if every window replacement in an HRB needs BSR approval.

Leaseholders

Check whether your building is an HRB before you get quotes. Your managing agent or accountable person should know.
Don't accept "we'll self-certify" from an installer for an HRB flat. Ask who will apply to BSR for approval, and allow for it in the timetable.
Check your lease and get landlord consent. Windows often form part of the external envelope, which the landlord usually controls.

Managing agents and accountable persons

Treat window works as a building safety matter, not a routine licence for alterations.
Make sure the work and its approval are recorded in the building's golden thread of information.
Consider a block-wide approach. One coordinated application can be more efficient than many individual ones.

Everyone

Build BSR approval time into the programme, and get professional advice early on whether the work is Category A or B.
Starting HRB work without the approval it needs is an offence, and it can cause problems when the flat is sold.

The bottom line

For now, the FENSA route is closed in high-rise buildings, and window replacements need BSR approval. The 2026 reforms suggest a lighter Category B process, and possibly a role for competent person schemes, but nothing is final. I'll update this piece when the government confirms the new Category A and B rules.

Sources

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