Policy confirmation that dual staircases will be required in new residential buildings of 18 metres and above has drawn a line under months of industry uncertainty. The move, framed as a nationwide measure, is being positioned as a life-safety upgrade to support evacuation resilience and firefighting access. Developers, designers and contractors now face a round of redesigns on schemes that were tracking the single-stair model, with programme and viability consequences likely to ripple through the pipeline. Local planning authorities are expected to reflect the change in decision-making, while building control bodies prepare for updated compliance checks. Supply chains are already signalling a pivot in core layouts, lift strategies and smoke control approaches. For a market under pressure to deliver homes at pace, this is a significant shift in design norms and delivery risk profiles.
TL;DR
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– New 18m-plus residential schemes will need two staircases, prompting redesigns and potential planning amendments.
– Expect impacts on net-to-gross, core size, lift and smoke control strategies, and programme.
– Transitional arrangements may apply, but the direction of travel is to plan for dual cores now.
– Watch for detailed technical guidance and how devolved administrations align their positions.
Design, cost and programme implications for 18m+ schemes
/> The immediate design impact is felt in core planning. Two independent protected stairways typically enlarge the core, influence corridor lengths, and may require reconfiguration of lifts, lobbies and smoke control systems. Some teams are revisiting scissor-stair options, but acceptability will depend on the finalised guidance and local interpretations. Net-to-gross is likely to tighten on typical floor plates, with potential knock-ons for unit mix, affordable quotas and façade ratios.
Contractors are weighing buildability and logistics. Wider cores affect MEP risers and distribution, acoustic separations and sequencing of formwork or modular assemblies. Firefighting shaft arrangements and pressurisation may need revisiting, with new coordination between services designers and façade teams to maintain compartmentation. Early procurement of doorsets, stair packages and smoke control equipment could become a critical path issue as specifications adjust.
Clients will scrutinise viability and programme float. Schemes approaching gateway decisions may pause to test dual-core options against investor requirements, especially where tight site footprints or daylight/sunlight constraints limit floorplate flexibility. Planning amendments could be required, and some projects may explore stepping down below the 18m threshold, using different massing or tenure mixes to protect deliverability. Consultants are advising that the safest commercial assumption is to design in the second stair now, even where transitional routes might exist.
# A likely on-the-ground scenario
/> A regional housebuilder is midway through RIBA Stage 3 on a 21m mixed-tenure block. The team’s single-stair layout delivers a clean unit mix, but the confirmation on second stairs triggers a redesign workshop. By moving to a dual-core arrangement, two 1-bed units per typical floor are lost, requiring rebalancing of the mix and re-running the daylight/sunlight analysis. The lift bank is split and the smoke ventilation strategy shifts from natural to mechanical to suit shorter corridors and protected lobbies. A minor material change to planning is prepared, and the contractor re-sequences the frame and MEP packages to account for revised riser positions and a longer lead-in for stair steelwork.
Regulatory pathway, sequencing and market signals
/> The policy sits within the wider post-Grenfell safety drive, and the market is treating it as the new baseline for tall residential. While headline direction is clear, project teams are awaiting the fine print on acceptable stair configurations, lobby requirements and how the rule interfaces with lifts, refuges and evacuation strategies. Building control sign-off will hinge on how swiftly guidance is embedded and how consistently it is interpreted, particularly on borderline schemes and mixed-use bases.
Pipeline effects will vary. Developers with near-term starts may lean on any transitional provisions, but lenders and insurers are already signalling comfort with dual-stair schemes over single-stair designs. Design-and-build contractors will seek early client decisions to avoid late-stage changes, and MMC providers will adapt modules to accommodate wider or twin cores. Local authorities will watch for unintended consequences, such as height-capping to sit just under 18m, and may push for design solutions that maintain density without compromising safety.
# What to watch next
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– The scope and clarity of technical guidance on stair separation, lobbying and smoke control.
– How planning authorities handle amendments and whether local policies reference the new requirement directly.
– Market responses on viability, including net-to-gross benchmarks and funding conditions tied to dual stairs.
– The stance of devolved administrations and the degree of alignment across the UK.
# Caveats
/> Details on implementation timelines and transitional arrangements can differ by jurisdiction and may evolve. Acceptable solutions, such as scissor stairs or combined cores, will depend on final guidance and the judgement of building control bodies. Mixed-use buildings and special typologies could see additional nuances that are not yet fully resolved.
The industry appears to be coalescing around dual-core design as standard for taller residential and will likely bake this into briefing documents and feasibility studies. The key question is whether smart planning and productisation can offset the net-to-gross and programme impacts enough to keep schemes viable at the volumes the market requires.
FAQ
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What exactly is changing for 18m-plus residential buildings?
The headline change is that new residential schemes above 18 metres are expected to incorporate two staircases for life-safety and evacuation resilience. This alters core layouts and the associated fire strategy, with knock-on effects for lifts, lobbies and smoke control.
# Does this apply to projects already in the pipeline?
/> Many teams are hearing that transitional arrangements may exist, but lenders and insurers may still prefer dual-stair solutions. The prudent approach is to seek advice on the specific stage of design, planning status and building control expectations for the scheme in question.
# How will this affect design efficiency and unit numbers?
/> A second staircase usually enlarges the core and can reduce net-to-gross on typical floors, sometimes affecting unit counts and mix. Designers can recover some efficiency through alternative layouts, façade optimisation and coordinated MEP strategies, but trade-offs are likely.
# Are there acceptable configurations beyond two completely separate stairs?
/> Industry discussion includes options like scissor stairs or different lobby strategies, but acceptability depends on the eventual technical guidance and local interpretation. Teams should avoid assuming equivalence until details are confirmed with building control.
# Is the requirement uniform across the UK?
/> The direction of travel is described as nationwide, but building regulations and guidance can differ in devolved administrations. Project teams should confirm the position with local regulators and align designs with the applicable jurisdiction’s rules and timelines.
