There is a Building Control deadline on 30 September 2026 and another on 1 October. They are unrelated, they were set by different parts of government, and they land within twenty-four hours of each other. If you have a residential scheme over 18m in the pipeline, both of them apply to you.
This piece is about the first one.
What changes on 30 September
The 2026 Approved Document B amendment booklet, issued with MHCLG Circular 04/2024, comes into force on 30 September 2026. Its content is short: second staircase provisions in residential buildings over 18m in height.
From that date, the guidance in Approved Document B expects new residential buildings at or above 18m to be served by two staircases. The policy has been settled since 2024 — the height threshold was lowered from the originally proposed 30m following consultation — and the long lead-in was deliberate. That lead-in is now nearly over.
Note what the amendment booklet is amending: Approved Document B 2019, incorporating the 2020, 2022 and 2025 amendments. If you are working from a version of ADB and are not sure which one, that is the question to resolve this month.
The transitional route, precisely
The old guidance continues to apply — but only on two conditions, and both have to be met.
Condition one: the submission. A building notice or an initial notice must have been given to, or a building control approval application with full plans made to, the relevant authority before 30 September 2026. Those three terms have the meanings given in the Building Regulations 2010. This is a date on a submission, not a date on a design freeze or a planning permission.
Condition two: sufficiently progressed. The work must have started and be sufficiently progressed either before 30 September 2026, or within the period of 18 months beginning on that day — so by the end of March 2028.
The circular defines “sufficiently progressed” tightly, and it is worth quoting the substance rather than paraphrasing it:
- New building: when the pouring of concrete for the permanent placement of the trench, pad or raft foundations has started, or the permanent placement of piling has started.
- Work to an existing building: when that work has started.
- Material change of use: when work to effect that change of use has started.
That is the same test used elsewhere in the building safety transitional arrangements, so it should be familiar. What it means in practice is that a submission alone does not preserve your position indefinitely. You get eighteen months to get concrete or piling in the ground.
An 18-month window sounds generous. Against a scheme that still needs its Gateway 2 approval, its discharge of conditions and its enabling works, it is not necessarily generous at all.
The other deadline, one day later
The Building Safety Levy starts on 1 October 2026. It applies to building control applications and initial notices submitted on or after that date, for major residential development — broadly 10 or more dwellings, or 30 or more purpose-built student bedspaces — and is charged per square metre of residential floorspace created.
So for a residential scheme over 18m at 10 units or more, the same submission date does two things at once. Made before 30 September, it opens the second staircase transitional route and falls outside the levy. Made on or after 1 October, it does neither.
That is not a reason to rush an incomplete application. A thin submission made to catch a date is a submission that comes back with questions, and the questions do not stop the clock on the 18-month progression test. But it is a reason to know, this week, which side of the line each of your live schemes sits on.
What to check before the end of September
Confirm the submission date on record, not the one in your programme. For each live 18m+ residential scheme, establish whether a building notice, initial notice or full plans application has actually been made — and get the date confirmed by the building control body, not from an internal tracker.
Check the height measurement. 18m is a threshold, and schemes sit close to it. If your scheme is near the line, resolve how the height is being measured under Approved Document B before you rely on being under it.
Work backwards from March 2028. If you are relying on the transitional route, put the foundation or piling milestone on the programme as a hard date and identify what could move it. Gateway 2 timescales, discharge of conditions and ground remediation are the usual candidates.
Don’t assume a redesign is a non-material amendment. Adding a second core generally changes unit numbers and mix. That is normally a Section 73 variation rather than a non-material amendment, which means a fresh round of consultation and, in London, potential referral to the Mayor — and it reopens the scheme to whatever the current policy position is, not the one you were consented under.
Sort the compliance evidence that will be needed anyway. Whichever side of the date a scheme falls, a complete Building Control submission is the thing that makes the rest of the programme predictable. The fabric, Part L and ventilation evidence is part of that package, and it is the part that can be prepared in advance rather than discovered late.
The point
The second staircase requirement is not new information. What is new is that the exit route from it closes this month, and the exit route is defined by an administrative act — a submission made to a building control body before a specific day — rather than by anything about the design.
Four weeks is enough time to establish where every live scheme stands. It is not enough time to fix a scheme you discover is on the wrong side of the line on 1 October.
If you have a higher-risk residential scheme where the Part L, SAP and fabric evidence needs to be complete and defensible before it goes to Building Control, get in touch and we’ll tell you how we’d approach it.
Sources: GOV.UK — Approved Document B (Fire Safety): new updates to support enhanced fire safety, MHCLG Circular 04/2024, 2 September 2024 · GOV.UK — Fire safety: Approved Document B · GOV.UK — Consultation response: Amendments to Approved Document B, second staircases