Project teams across England are racing to meet a fast-approaching cut-off for incorporating a second staircase in new residential buildings at or above 18 metres. The policy direction, signalled by post-Grenfell building safety reforms, is increasingly being treated by planning and building control as a firm expectation for qualifying schemes. Developers with designs currently in planning or pre-construction face a choice: redesign now, or risk missing transitional arrangements that may soon close. Contractors say clients are pushing for rapid core revisions to protect programmes, while fire engineers recalibrate evacuation and smoke control strategies for dual-stair layouts. The stakes are high because an added stair can reshape cores, reduce net saleable or lettable area, and drive cost plan adjustments, with knock-on implications for viability and funding. With the deadline described by many as imminent, clarity on timing and scope has become a material planning risk for the sector.
TL;DR
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– A cut-off for second staircases in new residential buildings of 18m and above in England is widely viewed as imminent.
– Redesigns to add a second stair can alter cores, unit numbers, MEP routes and cost plans, with potential planning and programme effects.
– Transitional arrangements are narrowing, so teams are weighing quick redesigns versus risking re-submission later.
– Early engagement with planners, building control, fire engineers and funders is becoming critical to keep schemes moving.
Design, programme and cost implications across the 18m threshold
/> For contractors and consultants, the immediate implication is technical: moving from a single to a dual-core or split-core arrangement affects structural grids, lift banks, riser positions and smoke control provisions. Architects are reporting the need to re-optimise flat layouts and common parts to recover net area, while MEP designers re-route services and reassess plant capacity and resilience. Cost managers are revisiting assumptions on common area finishes, doorsets, smoke control and ventilation, while factoring in potential changes to facade continuity at new core interfaces. Housebuilders and build-to-rent clients are also rechecking unit mixes, amenity spaces and compliance margins, noting that even marginal height reductions below the threshold may affect value and planning acceptability.
Programme-wise, additional design iterations, fresh fire strategies and potential non-material amendments to planning can compress pre-construction timelines. Procurement teams are flagging lead times for stairs, core walls, doors, smoke ventilation systems and lifts, with sequencing adjustments needed where stair installation becomes a critical path item. Building control sign-off may hinge on up-to-date documentation that reflects the dual-stair approach, prompting earlier and more frequent coordination among dutyholders.
On the ground, a typical mid-rise scheme in a regional city might pivot from a single stair to a dual-core layout just weeks before tender. The shift reduces net floorplate efficiency, nudges the unit count down, and repositions risers to suit revised escape distances. The contractor is asked to re-sequence enabling works, while supply chain partners reprice core packages and flag longer lead-ins for compliant doorsets and smoke control equipment. The client seeks a swift planning variation to keep dates intact, and the lender requests clarity on programme, pre-sales and updated appraisals. Even if the redesign is contained, the lost time and rework can push the start on site and increase prelims exposure.
Deadlines, transitional arrangements and the road ahead
/> Industry reports suggest transitional windows are narrowing, with local planning authorities and building control bodies increasingly steering schemes above 18m towards two-stair solutions. Where designs have not yet locked in, many clients are opting to redesign now rather than test the limits of short-lived concessions. In-flight projects are navigating case-by-case discussions on whether a non-material amendment suffices, or if a more substantial submission is needed. The supply chain is preparing for higher volumes of stair, core and life-safety packages, but insists that early visibility of design intent will be crucial to avoid pinch points later in the year.
# What to watch next
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– Signals from planning and building control on how strictly the 18m threshold is being applied to late-stage schemes.
– Any further government guidance or circulars clarifying transitional cut-offs and documentation expectations.
– Shifts in insurer and lender stances on single-stair designs above 18m, especially for schemes seeking finance.
– Evidence of supply chain constraints on core components that could extend programme durations.
# Caveats
/> Rules and interpretations can differ by location and building type, and devolved administrations have their own regimes. Some design teams argue that carefully engineered evacuation strategies and resilience measures may address risk in certain contexts, but acceptance sits with the relevant authorities. The emerging position is also not a substitute for project-specific legal or regulatory advice, and developers should expect case-by-case scrutiny.
The direction of travel is towards more conservative, evacuation-friendly core design in taller residential blocks. The industry’s test over the next quarter is whether it can absorb redesigns at pace without derailing delivery targets, and whether funders, planners and contractors can align quickly enough to keep viable schemes moving.
FAQ
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What is meant by a “second staircase” in the 18m context?
It refers to providing two independent escape stairways in new residential buildings that meet or exceed an 18-metre height threshold. The intent is to improve resident egress and firefighter access, reducing reliance on a single route. How this is implemented is subject to design development and approval by the relevant authorities.
# Which projects are most likely to be affected?
/> New-build residential schemes in England at or above 18 metres are the primary focus. Projects currently in planning, detailed design or pre-construction are seeing the greatest pressure to adapt. Conversions that create new dwellings at similar heights may also attract scrutiny, while lower-rise buildings generally fall outside this threshold.
# Do schemes already in planning or under construction have to change?
/> Transitional arrangements may permit some in-flight schemes to proceed under previous assumptions, but the window for that appears to be narrowing. Many authorities are increasingly expecting compliance for qualifying designs, especially where significant approvals or submissions are still outstanding. Teams should confirm positions with their planning and building control contacts for each project.
# How might adding a second staircase affect layout and cost?
/> A second stair typically increases core area, which can reduce net saleable or lettable space and alter unit layouts. Designers often need to revisit structural grids, lift numbers and MEP routes, and fire strategies may require fresh modelling. Cost plans can move accordingly, though some losses may be mitigated through layout optimisation and specification choices.
# What practical steps can teams take now?
/> Confirm how the building’s height is measured for threshold purposes and test dual-stair options early. Engage with planners, building control and fire engineers to agree a path through approvals, and factor design iterations into programme risk. Keep funders and insurers updated, as their position on single-stair schemes above 18m is increasingly cautious.
