Until 2023, the United Kingdom did not establish a maximum building height for single stair residential buildings (flats).

The UK’s prescriptive building regulations do not establish a vertical constraint for single stair conditions, rather limiting single stair design only horizontally with maximum travel distances and an occupancy load limit of 60 people per storey. Existing high-rise residential buildings in the UK were designed with a shelter-in-place fire evacuation strategy, such that only occupants from the flat where the fire occurs will immediatelly evacuate to avoid crowding of the exit. All other occupants remain in place until explicitly ordered to evacuate. This is also known as the ‘stay-put’ policy.

On June 14, 2017, one such building, the Grenfell tower, was engulfed by the deadliest residential fire in the United Kingdom since the Second World War and cost the lives of 72 people. The negligent use of combustible insulation for the retrofit cladding material caused the rapid spread of the fire up the building facade. The tower consisted of a 24-storey concrete structure with a single exit stair. At the Grenfell inquiry, experts testified that the shelter-in-place evacuation policy was sustained for more than 80 minutes beyond the point at which a general evacuation should have been ordered.

Largely in response to the Grenfell disaster, the government announced new fire safety regulations in 2020, which require fire sprinklers for all residential buildings over 11 meters in building height, require increased evacuation signage, forbid the use of combustible materials in exterior wall assemblies and demand increased oversight during planning and construction.¹ The full list of regulations, made available by the Ministry of Housing, Communities & Local Government, is titled “A reformed building safety regulatory system”. Notably, the new regulations did not include any changes to require second staircases and do not establish a relationship between the stay-in-place evacuation policy and the unrestricted height for single stair buildings.

In London alone there are currently 510 high-rise towers in planning and 115 in construction. Since 2014, 122 such projects have been completed and in the next 2 years, 96 such towers are expected to follow.²

The UK building code is described here because the Grenfell Tower disaster is sometimes cited as argument against allowing single stair buildings in Canada. Certainly the lack of a second means of egress contributed to the number of deaths at Grenfell, however the 24-storey  tower far exceeds the scale of this code change request, which is proposed only for sprinklered buildings of up to six storeys.
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