FIRE SAFETY | MULTIPLE STAIRCASES that deviate from guidance remains available, provided they are substantiated properly. The consultation seeks to amend statutory guidance in AD B to reduce some of the uncertainty that exists around what is a common building, says Schulz, with AD B providing fire-safety guidance on this. There is no change to Building Regulations or a legal ban on single staircases above 30m proposed, she adds. That this [performance-based designs] route remains available is important, as not every site will be able to accommodate a two-stair solution and as the consultation document hints, it is possible to arrive at a bad two-stair arrangement that has numerous single points of failure, despite, on paper, having two stairs. However, Schulz approves of the proposed changes to AD B. We support the clarity that the changes will bring around when a second stair is expected to be provided in new residential buildings, as significant uncertainty exists at present, she says. Stephen Jeffery, chief technical officer at Mace, agrees that any unambiguous, clear guidance on fire safety is welcome. However, he says the proposal needs to be coordinated with design codes such as BS 9991, so that code-compliant designs become the norm and there is less reliance on fire-engineering solutions, which are often required to overcome poor design decisions made in earlier works stages. Jeffrey points out that some developers are already seeking to apply the forthcoming proposed standards regarding single staircases and fire safety: We have raised the issue of single-staircase buildings with a number of our clients, and were pleased to see them take the decision to apply the principles outlined in the draft version of BS 9991:2021 and instruct redesign to provide a second staircase and evacuation lift provision in advance of the publication of the new standard. AD B already includes guidance on the provision of more than one common stair in buildings taller than 11m, says Jeffrey. Since the HSE [Health and Safety Executive] has become a statutory consultee in planning gateway one, designers have to address fire safety before planning permission is granted, he adds. A trigger height of 30m also aligns with enhanced requirements for fire resistance of the superstructure, which already exist within the guidance. Ben Cooper, director of independent firm Orion Fire Engineering, is equivocal about the consultation. On the one hand, he believes singlestair residential towers can be designed and constructed in a safe and robust manner. This has been demonstrated with some recent fires in new-builds that were contained properly within the compartment of 40 February 2023 www.cibsejournal.com origin through correctly constructed compartmentation, sprinkler protection and other life-safety measures recommended under guidance issued from 2015 onwards, he says. On the other hand, Cooper says many residential towers are not built to the appropriate standard. He cites reviews of fire-protection measures that have revealed that subcontractors have substituted products specified in the technical designs without ensuring they adhere to the firesafety strategy, or even recording such substitutions. With that in mind, perhaps we do need tighter legislation to add an additional layer of resilience, he says. Its an unfortunate fact that things will go wrong, and things will be missed, irrespective of any claims of competence, accreditation or certification. This legislation addresses the weakest links in our industry and will undoubtedly create safer homes. Design steps The number of stairs provided in a building is a fundamental design decision that shapes not only fire-safety design, but also architectural arrangements,