A key compliance cut-off is fast approaching in England for new residential towers at and above 18 metres, with industry attention converging on the requirement for a second staircase. Developers, housebuilders and build-to-rent operators are weighing whether marginal schemes can still progress under transitional arrangements or must pivot to redesigned cores. Consultants say planning authorities and funders are increasingly taking a conservative line, nudging even borderline or previously consented schemes toward two-stair solutions. On live projects, that is translating into core rethinks, apartment reconfigurations, smoke-control revisions and rebaselined programmes. Contractors are reporting renewed preconstruction activity as teams probe structure, services and precast availability to accommodate the change. With the Building Safety Regulator now embedded in the approvals landscape for taller homes, few in the market expect room for single-stair exceptions to widen. The direction of travel is clear: two means out for 18m-plus homes is moving from policy debate to delivery detail.
TL;DR
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– The looming compliance point for England’s 18m-plus residential towers is pushing schemes toward two-stair designs, even where transitional routes exist.
– Expect design teams to rework cores, lifts and smoke-control strategies, with potential trade-offs in net area, viability and programme.
– Funders, insurers and planning bodies are widely seen aligning with a two-stair default, shaping choices beyond the letter of guidance.
– Teams should clarify local interpretations early and build in supply-chain and approval time for amended designs.
Design, procurement and approvals: what it means for the market
/> For designers, adding a second protected stair typically drives a broader replan of the core: more space for escape routes, adjusted lift banks, enlarged lobbies and changes to riser positioning. Fire strategies are being revisited, with different approaches to lobby protection, ventilation and pressurisation under review to align with two independent means of escape and firefighting access. That can shave net sellable or lettable area, especially on tight footprints, and may trigger reappraisals of unit mix, amenity locations and structural grids. In mixed-use towers, interfaces between residential cores and non-residential floors are under closer scrutiny to avoid unintended consequences for travel distances and smoke control.
For contractors and suppliers, programme risk is moving centre-stage. Core reconfiguration affects reinforcement detailing, slipform or jumpform sequencing, and precast stair and landing packages—products that may already be under pressure. Mechanical and electrical design needs fresh coordination, with knock-ons for vertical distribution, plant sizes and heat/smoke exhaust routes. Early engagement with building control and the fire engineer is becoming standard to reduce late-cycle change and to de-risk Gateway submissions where applicable.
For clients, approvals strategy is pivotal. Where designs had progressed under earlier interpretations, minor material amendments or section variations may be needed at planning, followed by new packages for building control. Market chatter suggests some funders and insurers are now conditioning support on two-stair compliance irrespective of technical transition pathways. That can tilt viability calculations, but it may also enhance asset liquidity and marketability, particularly in London and other dense urban centres where occupant reassurance carries weight.
On the ground: redesigning an 18m-plus tower
/> Consider a regional scheme planned at just over 18 metres, with tender drawings near completion. The project team pauses to test whether the core can carry a second stair without materially compromising unit numbers or daylighting. Architects rotate lift cars and introduce a compact secondary stair on the opposite side of the core, while the engineer rationalises columns to recover floorplate efficiency. The fire engineer revises lobby layouts and smoke-vent strategies, and the MEP lead re-routes risers to preserve kitchen and bathroom stacking. The contractor refreshes the preconstruction programme, flags longer lead times for precast elements, and proposes resequencing early works to maintain a start-on-site target. Planning advisers prepare a modest design amendment, aiming to keep elevations stable while evidencing improved egress and firefighting access.
The practical upshot is a short-term delay and some loss of net area, offset by clearer compliance and a smoother path with funders. Project contingencies are revisited, with provisional sums for core trade packages adjusted to reflect new quantities and coordination risk. The client signs off the redesign, judging that certainty of deliverability in a tightening regulatory climate outweighs the hit to appraisal metrics. While each scheme will differ, this is the sort of recalibration many teams are now making as the deadline sharpens decisions.
Decisions ahead and areas of uncertainty
/> Project pipelines will likely split between schemes that can still evidence compliant progression under transitions and those opting to switch regardless, often driven by lender expectations. Regional planning bodies may continue to take varied stances on “materiality” thresholds for amendments, making early dialogue critical. Teams delivering student and build-to-rent assets are expected to keep converging on two-stair baselines to align with operational management plans and evacuation policies. Across the supply chain, the practicalities—design bandwidth, approvals slots and product availability—may be as determinative as policy wording.
# What to watch next
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– How building control bodies and the Building Safety Regulator interpret transitional positions on live projects seeking Gateway approvals.
– Whether planning authorities lean toward streamlined amendment routes for two-stair conversions that leave massing and façades largely unchanged.
– Signals from major lenders and insurers that normalise two-stair expectations across all 18m-plus residential asset classes.
– Supply-chain capacity for core systems, from precast stair flights to lobby doorsets and smoke-control components, through the next two quarters.
# Caveats
/> Local interpretations vary, and some authorities or funders may set expectations above the minimum thresholds, so scheme-specific advice remains essential. Transitional arrangements are complex and depend on project status and evidence of progress, which can be read differently across jurisdictions. Some design impacts may be mitigated by clever planning, but not all footprints will yield the same efficiencies. Teams should expect evolving guidance and be prepared to adapt as clarifications emerge.
The balance of opinion points to two stairs becoming the settled norm for new English residential towers at 18 metres and above. The open question is how efficiently the industry can lock designs and approvals without derailing delivery timetables in a stretched supply chain.
FAQ
# What is meant by the “second staircase” in 18m residential towers?
/> It refers to providing two independent protected means of escape for occupants in new residential buildings at or above 18 metres in England. In practice, that usually means a second stair core, alongside associated protected lobbies and firefighting access arrangements. The policy intent is to strengthen life safety and resilience in evacuation scenarios.
# Does the requirement apply to schemes already in the pipeline?
/> A government transition period has been signalled, and some in-flight projects may still progress under earlier provisions if they meet specific progress tests. However, many planning bodies, funders and insurers are seen favouring a two-stair approach regardless, particularly for taller schemes. Teams should confirm the position with planning and building control early.
# How will this affect design, cost and programme?
/> A two-stair core typically enlarges the service zone, which can affect apartment layouts, net area and structural grids. Fire and MEP strategies often need rework, with knock-on effects for plant sizing, risers and smoke control. Costs and timelines will depend on the footprint and stage of design, but additional coordination and procurement time are commonly reported.
# Is this only for pure residential, or does it cover mixed-use towers too?
/> The focus is on residential buildings at or above the 18m threshold, including mixed-use developments where residential elements are served by dedicated cores. Non-residential floors may be governed by different provisions, but interfaces can complicate escape and firefighting strategies. Project-specific advice is needed where uses overlap.
# What should project teams prioritise as the deadline approaches?
/> Most teams are stress-testing core options, confirming local interpretations with planning and building control, and talking to funders and insurers about expectations. Early engagement with fire engineers and contractors can reduce redesign loops and help re-sequence procurement. Keeping a clear audit trail of decisions and progress will also support any transitional case a scheme intends to make.
