The new second staircase mandate for residential buildings over 18m — timelines, exceptions, and design implications.. The Second Staircase Mandate From 30 September 2026, all new residential buildings over 18m in England must have at least two staircases. Key Requirements Applies to buildings with a top storey above 18m containing residential units Both staircases must be fire protected (minimum 60 minute fire resistance) Staircases must be located to provide alternative escape directions Lobbied approach required for buildings adopting simultaneous evacuation Evacuation lifts required alongside the second staircase Exceptions Buildings with planning permission granted before 30 September 2026 Conversions of existing single staircase buildings Buildings below 18m (though fire engineering justification may require two stairs) Cost Impact Industry estimates suggest the second staircase requirement adds 5 8% to construction costs for buildings in the 18 30m range. For second staircase design consultancy, contact us.