Looking ahead to the new second staircase guidance

This article was originally published in CoStar on 7 April 2025.

From 30 September 2026, second staircases will be mandatory for all new residential buildings over 18 metres in height.  There is a transitional period for schemes where a building control application has been made before 30 September 2026 and the building work has been sufficiently progressed within 18 months of that date, subject to which, the current rules will continue to apply. 

Impact on viability

Adding a second staircase will typically reduce the saleable/lettable floor area in a scheme. This has a knock-on negative effect on viability. In order to get around this viability challenge, developers are likely to need to increase the height, scale or massing of the development to make up for the floor space lost to the second staircase. Another potential resolution to this is to change the sizes of dwellings or tenure mix or reduce amenity space. This may lead to a loss of affordable housing units through viability arguments, particularly in locations where higher rise buildings are more common – typically in cities or town centres, where site constraints mean it may not be possible to increase the footprint size of the building.

Schemes of around 18 metres in height where it isn't possible to increase the footprint of a proposed building are likely to either have to be built below 18 metres with a single staircase or significantly above that height to provide sufficient additional floors to offset the additional cost and floorspace lost due to the second staircase. This is likely to lead to smaller numbers of buildings between 7 and around 10 stories being constructed.

Impact on developers

In the build to rent sector, there is concern that from an investor/lender perspective, there could be an increasing wariness in relation to buildings with a single staircase which, if subject to the new rules, would have required a second staircase. This could devalue these buildings. For this reason, developers have been and are considering including second staircases for buildings which could otherwise be constructed before the new rules apply.

When the 18 metre height limit was confirmed in July 2023, because of the lack of detailed technical guidance given, many schemes over 18 metres were simply put on hold. The transitional period will hopefully give sufficient time for the majority of schemes currently in progress to be completed under the existing rules. 

However, any existing schemes which are caught by the new rules will need a fresh building regulations application which complies with the second staircase rules. This will in turn require a re-design of the building and a variation to any existing planning consent or a new consent.  The increase in cost and the associated delays of this are a further hit to an industry already under significant challenges around viability and delays.