As of today, 30 September 2026, the amended Approved Document B guidance takes effect in England for new residential buildings where the top storey is 18 metres or more above ground level. These buildings must be served by more than one common staircase.
This is not simply a fire strategy update. For developers, architects, main contractors and specialist subcontractors, the second staircase affects net-to-gross efficiency, structural coordination, Gateway 2 approval, procurement, programme risk and the way insurance responsibilities need to be agreed.
The change also arrives at a difficult point for many schemes. Some London projects have already faced a practical design freeze deadline well before today because adding a core can affect the viability of the whole development. Others are being reworked, delayed or shelved while the design team assesses the commercial impact.
Why the threshold is 18 metres
The original government consultation focused on a second staircase for new residential buildings above 30 metres. That proposal was subsequently reduced to 18 metres following consultation responses and industry debate.
The reason is that 18 metres aligns more closely with the Building Safety Act definition of a higher-risk building. It also provides a common reference point for the more demanding building safety and fire safety controls that apply to taller residential buildings.
The final position is therefore not just an arbitrary height limit. It brings the second staircase requirement into the same broad risk area as the higher-risk building regime, where the Building Safety Regulator and Gateway process become central to design and construction approval.
The government’s Approved Document B circular and amendment information confirms that the 2026 amendments apply in England and introduce updated guidance for second staircases in residential buildings with a storey 18 metres or more in height.
The rule is also more specific than simply drawing two lines on a plan. Interlocked stairs, scissor stairs and stacked stairs do not count as compliant alternatives to the required provision of more than one common staircase. The design must provide a genuine, workable escape strategy that can be understood, built, inspected and maintained.
The commercial consequence is larger than the core
A second staircase takes up more than the physical area of the stair itself. It brings additional corridors, protected lobbies, risers, smoke control requirements, fire doors and structural coordination. On a tight urban site, particularly in London, that can remove saleable or lettable floor area from every level.
This affects the net-to-gross ratio and can change whether a scheme meets its financial model. A design that appeared viable with one core may need a different apartment mix, a revised structural grid, altered façade geometry or a different servicing strategy once the second staircase is introduced.
That is why many schemes are facing what is effectively a design freeze deadline earlier than the legal compliance date. Developers cannot wait until construction documents are nearly complete to discover that an extra core will reduce value or require a significant planning amendment.
In practice, the decision can move quickly from “we need to coordinate one more stair” to “we need to reconsider the whole building”. That creates a commercial risk for every contractor pricing the work, particularly where the design appears mature but key fire and access decisions remain unresolved.
Gateway 2 makes late redesign especially disruptive
For a higher-risk building, Gateway 2 is not a paperwork exercise that can be separated from the design. The Building Safety Regulator expects a detailed building control approval application before the relevant construction work begins, and the submission needs to demonstrate that the design is sufficiently developed and coordinated.
The staircase strategy sits within the same approval chain as the fire strategy, structural grid, MEP routes, façade logic, evacuation arrangements and buildability evidence. Changing the stair after these matters have been coordinated can require much more than updating a floor plan.
A second core may conflict with transfer structures, plant rooms, drainage routes or façade openings. It may affect fire-fighting access, smoke ventilation and the location of evacuation lifts. It can also change the sequencing and temporary works required on site.
From an insurance perspective, late redesign is a warning sign because it can create uncertainty about who designed what, who reviewed the change and whether the contractor has accepted any design responsibility by pricing or proposing a solution.
The Building Safety Regulator planning guidance is a useful reference point, but contractors should also obtain project-specific advice from the design team, the client and the relevant building control authority.
The site risk is in the details
A second staircase creates new compartmentation lines. The associated corridors, lobbies and risers must be correctly designed and constructed so that the escape routes retain their intended fire performance.
This is where projects often become vulnerable. Fire doors, frames, ironmongery, cavity barriers, service penetrations and fire stopping can be treated as late-stage details, specified under time pressure after the main layout has already been agreed. That approach is risky.
A fire door that is the wrong type, badly fitted or installed without the correct certification can undermine the compartment. The same applies to fire stopping around cable trays, pipes and ductwork. The physical work may look complete while the evidence needed to demonstrate compliance is missing.
For contractors, this is both a quality risk and a liability risk. A defect may later be described as a design failure, a workmanship failure, a coordination failure or a failure to follow the specification. Those descriptions can lead to very different insurance responses.
Where construction insurance becomes relevant
Construction Contractor Insurance needs to reflect the actual role being undertaken, not just the trade description on a proposal form. A contractor involved in a higher-risk residential project may be carrying responsibilities for temporary works, design coordination, installation details, fire-stopping interfaces or design development that are not obvious from the contract title.
General Contractor Liability Insurance is important, but public liability is not a substitute for professional indemnity. Public liability is generally concerned with injury or damage caused by an accident, while professional indemnity is more likely to respond to allegations arising from negligent design, specification, advice or professional services.
The difficulty is that fire-related disputes often sit between the two. If a fire door fails because it was incorrectly designed or specified, the issue may be treated as design liability. If the door was correctly specified but installed incorrectly, the argument may move towards workmanship and public liability. If the details were changed during construction without clear approval, the position can become more complicated still.
Professional indemnity policies also frequently contain fire-related sub-limits or exclusions. A policy with a large headline limit may have a much smaller amount available for fire safety, cladding or certain residential building risks. That sub-limit may not be remotely adequate for remediation costs across a multi-storey building.
Contractors should also remember that compliance with Building Regulations is not the same as having broad insurance protection. Failure to comply with Building Regulations can be a criminal offence, and insurers may apply their own underwriting standards even where a design team believes the minimum regulatory position has been met.
Insurers are often concerned with property protection and loss severity as well as life safety. They may look to guidance from organisations such as RISCAuthority, or ask for additional controls that go beyond the minimum route described in Approved Document B. A contractor can therefore be technically compliant and still find that the insurer, lender, warranty provider or client expects a higher standard of evidence and protection.
What contractors should check now
Contractors in Essex, Kent and London should first establish whether the core strategy on each relevant scheme is genuinely frozen. If the stair arrangement, fire strategy or major service routes are still moving, the project may not be as ready for procurement as it appears.
The biggest warning sign is unresolved design pretending to be mature enough for procurement. Pricing a package before design responsibility and coordination risk are properly allocated can leave a contractor carrying an uninsured or underinsured exposure.
Before pricing or signing, confirm who is responsible for the staircase design, fire strategy, fire-stopping details, temporary works and design changes. The contract should identify whether design liability remains with the architect, engineer, specialist designer or main contractor, and the required insurance limits should be agreed at the same time.
Check the professional indemnity wording carefully, including any fire-related sub-limits, exclusions for higher-risk residential buildings and restrictions on design-and-build services. Do not rely on the policy schedule alone. The operative policy terms and endorsements matter.
Contractors should also review Contractors All Risks cover, including the treatment of defective work, resulting damage, testing and commissioning. Contractual warranties, collateral warranties and fitness-for-purpose obligations can materially increase exposure beyond ordinary negligence, so they should be reviewed before acceptance.
Finally, keep the golden thread evidence complete. This should include approved drawings, design changes, product information, fire door and fire-stopping records, inspection photographs, installation certificates, test results, approvals and clear responsibility records. Good documentation will not correct defective work, but missing documentation can make a defensible position much harder to establish.
A practical insurance review for today’s projects
The second staircase rule is a fire safety requirement, but its effects run through the entire construction risk profile. It can affect the value of the development, the design programme, Gateway 2 approval, procurement, workmanship controls and the allocation of professional responsibility.
For contractors, the immediate priority is to identify projects where the design is still changing and then make sure the contract and insurance arrangements reflect that uncertainty. A lower premium is not useful if a fire-related sub-limit, design exclusion or contractual warranty leaves the business exposed to a major claim.
Moyak Insurance Services provides an individual approach to business insurance for growing and established companies. As a business insurance broker in Essex, Kent and London, we can review your Construction Contractor Insurance, General Contractor Liability Insurance, professional indemnity requirements and wider business protection before you commit to a project.
For a practical discussion, contact Moyak Insurance Services at info@moyakinsurance.co.uk or 01375 392087. You can also visit Moyak Insurance Services and read our guide to underinsurance mistakes in general contractor liability insurance.
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