The long-awaited fire safety measure marks a stricter threshold than the 30m rule introduced by Sadiq Khan in London in December, with Gove saying the announcement would “provide much-desired clarity”.
The government said the move was responding to “calls from the sector for coherence and certainty”.
But the Department for Levelling Up, Housing and Communities (DLUHC) also said the change, which has been under consultation since the start of the year, would be a “considered and gradual evolution of safety standards”.
It added: “The government is clear that this new regulation cannot jeopardise the supply of homes by disrupting schemes that have been planned for years.”
DLUHC said it planned to work rapidly with industry and regulators over the summer to design transitional arrangements that would secure the viability of projects already under way, “avoiding delays where there are other, more appropriate mitigations”.
The Royal Institute of British Architects (RIBA) called the adoption of an 18m threshold “a huge win for fire safety standards”.
President Simon Allford said: “This is a significant moment. Over six years on from the Grenfell Tower tragedy, it is hugely positive and reassuring to see the government listening to the united call of experts on fire safety, bringing greater coherence and certainty for industry.”
RICS global building standards director Gary Strong added: “The UK government announcement today shows they have taken heed of what other countries including Scotland have already done, what expert bodies such as the RICS have been saying, and ensures there is resilience against a single point of failure when it comes to fire safety.
“We urge the government to deliver on this announcement and legislate second staircases in new residential buildings over 18m as soon as possible.”
Eddie Tuttle, director of policy, research and public affairs at The Chartered Institute of Building, said the institute was delighted with the government’s decision, calling an 18m threshold the best solution to ensuring the safety of residents and emergency services workers.
Despite a warm welcome from regulators, the new rules are expected to affect the viability of residential schemes. One agency warned that projects with a total of 123,000 new homes were at risk of being delayed or cancelled following the mayor’s rule change in London.
Khan’s introduction of a second staircase requirement in all new London buildings taller than 30m had sought to get ahead of wider government plans for a 30m threshold, which have been under consultation since the start of the year.
In March, a coalition including RIBA and other built environment bodies called on Gove to reduce the proposed 10-storey threshold for additional staircases to six storeys, or from 30m down to 18m.
Source: Property Week