Office to apartment conversions
The fire safety hazards of ‘quick-fix’ repurposing of commercial buildings for residential housing
The many fire safety hazards and challenges involved in repurposing commercial premises for residential housing – an activity that has become more commonplace following the COVID-19 pandemic.
The UK government’s introduction of fast-track ‘Mercantile-to-Abode’ (MA) PDR conversions (Commercial-to-Residential Permitted Development Rights), announced this year, raises demanding questions for risk management as the new rules mean that Local Planning Authorities (LPAs) can give provisional approval for developments that bypass normal planning rules.
Major repurposing of commercial buildings will certainly prove challenging for those ‘responsible persons’ charged with the fire safety of premises formerly designed for open-plan office use. The changes will undoubtedly require a new mind-set for those affected.
The impact of the COVID-19 pandemic on how real estate is utilised and occupied is predicted to be critical factor in the UK’s economic recovery, further compounded by a chronic housing shortage. The post-Covid future of working from home (WFH) and the decline of high street retail, driven by the phenomenal growth of online shopping, are also bound to be an added influence on the trend towards commercial to residential conversions.
It is timely, then, to attempt to identify the emerging risks that could arise from the current trend towards ‘Adaptive Reuse’.
The challenges of open-plan conversion
To consider the question of large open-volume spaces – such as the industrial buildings so sought-after for fashionable ‘loft living’ – a practical specimen case is needed. Here, therefore (see diagrams), the challenging issues prompted by PDR commercial conversions are illustrated by a three-storey office block with open-plan floors (dia. 1) each floor with area of 2500sq. m (not including plant for services) surrounding an inner courtyard. There are four helical staircases (one at each corner of the site).
Large open plan offices are of greater height than residential and in this specimen case, the floor-to-ceiling height is 3.2m with pre-cast floor units spanning 14m to achieve unobstructed space. So, you might think, the perfect canvas – virtually blank – for residential conversion.
However, try to imagine resolving the complexities of its adaptation for domestic use: Equitable access to lifts (there are two lift shafts at the north west corner); complete reconfiguring of plumbing, ducts and risers for ventilation, heating and utilities; adjusted load-bearing criteria; repurposing washrooms and storage… not forgetting the immense challenges for compartmentation. And, critically, solving the problem of appropriate fire stairs and means of escape for the occupants of 40 apartments on each of three floors.
Conundrum of compartmentation
Yet, according to fire safety specialists and building technologists invited to comment on the fire safety for such a modern building, the exit configurations proposed are a fire hazard.
Some might argue that the significant fire safety problems identified here for a MA conversion of this type are emphatically not insoluble BUT when a complete overview of this model of ‘mercantile’ structure – designed specifically for flexible open-plan offices – becomes clear you’ll understand the misgivings. For example, in the view of a prominent building consultant, the repurposing of this kind of ‘architectural legacy’ for apartments (a circa mid-1990s office block) presents a technical challenge that is not ‘straightforward’, particularly the adaptation of the ventilation, fire separation and drainage to meet building regulations and housing standards.
Compromised residential compartmentation
Principally, for this type of MA conversion, the drawbacks to apartment compartmentation are as follows:
- Constrained sunlight: Open-plan offices with taller ceilings permit daylight to penetrate deeper into the building, which is important for the well-being of occupants. In addition, light-coloured ceilings improve daylight reflectance. By simply bisecting an open-plan floor, with a compartmented route for access and exit, those apartment sub-areas (such as a bedroom or bathroom) nearest to the route (i.e. in the depth of the building) will be disadvantaged by a significant loss of daylight.
- Ventilation: For a building of pre-cast concrete modules, the thermal mass of the concrete absorbs daytime heat gain and the high ceilings are constructed for thermal stratification at levels designed to moderate temperatures for the interiors. In short, the main ‘green strategies’ of such an open-plan building are maximisation of daylight and engineered natural ventilation. In regard to both, any major restructuring project for interpenetrating compartmentation has life-critical implications for the behaviour of smoke-spread in the event of fire in an open-plan building repurposed for residential use.
- Means of escape – conflicting views: You’ll note two examples (Diagrams 2 and 3) of access and exit route configurations are prompted by this specimen of an MA conversion, a representative problem of compartmentation in which we examine means of escape from 40 apartments on the first floor of a residential block with four helical staircases. In the first draft (Dia. 2) outlined by the building technologist we consulted, you’ll see the route is ‘orbital’ on the assumption that access to four staircase-exits would afford fourfold means of escape in the event of an emergency.
This proposal was countered by the view of the fire safety specialist who states: “In theory a Fire Service would not oppose open-plan layout where appropriate fire safety measures are provided, but for this particular example, consideration of ventilation, sprinklers, lobbies, dry/wet risers, the height of the building, the use of an alternative (non-helical) stair for fire-fighting purposes, travel distances etc. would be necessary. However, typically, this would all be addressed in the Building Consultation phase. Evidently, the building has been designed using fire engineering, and as such may need to have further consideration when the change of use occurs. It will need to comply with the functional requirements of Approved Document B or BS 9991 and be managed appropriately. Escape from these elements would be considered to be using a single stair [non-spiral], and so consideration should be given to Figure 6 or 7 from BS 9991 : 2015. (Similar requirements are set out in Diagram 3.7 of Approved Doc B, vol 1.)‘
- Travel distances for single direction escape: From the latter corrective observations, we can see that travel distance limits for single direction escape to an assigned staircase lobby became a deciding factor for the revised Diagram 3 route configuration. In other words, the apportionment of one fire staircase to 10 apartments, which confounds the value of an orbital ‘fourfold means of escape’ proposed in Diagram 2.
Non-helical stair for firefighting: an unresolved puzzle
Our major quandary remains, however, because if regulatory exit route travel limitations define the requirement for access to a ‘necessary’ non-spiral staircase for fire-fighting purposes, how will the developer resolve the future ‘repurposing’ of four spiral stair towers, at each corner of the building, seemingly defunct for fire services entry?
These are not entirely theoretical concerns because similar conversion projects are currently taking place. Study of the former open-plan floor under discussion (dia. 3) reveals an inequality now apparent between occupants in apartments with outlooks from the outer façade and those in the apartments overlooking the inner courtyard. If it were an open-plan office, as in its former use, it’s clear that – in a fire emergency – all office occupants had clear unobstructed access to the more visible outer façade, something now denied to occupiers of apartments confined to the inner courtyard aspect.
Initial conclusion? Change of use can mean change of safe guarding.
Fire strategy… a virtuous circle of decision-makers
To better understand the challenges involved when repurposing commercial buildings to residential accommodation, we spoke to the IFSM (Institute of Fire Safety Managers). They point out that ‘many large buildings like traditionally built factories, mills and inner-city warehouses’ have been subjects of conversion to apartments over many years.
In some cases, as IFSM President Dr. Bob Docherty points, there have been ‘rogue’ developers and
“… lack of enforcement at the time of conversion has resulted in buildings that are not fit for purpose… I can think of one building in Salford that had a total lack of compartmentation; lack of firestopping; lack of full fire resistance between apartments; partitions not sealed and closed at compartment junctions; fire doors not installed correctly; fire alarms installed by electricians who are not fire alarm engineers… and that’s before we looked at the means of escape in the common areas!”
A prohibition notice was served on this building.
The pathway towards prudent fire safety for conversions is clear, as the IFSM president sums up:
“With proper plan submissions and liaison between enforcing authorities, use of third party accredited installers and builders, and the production of a proper ‘Fire Strategy’ document for the conversion which sets out all the fire safety details for the purpose group the building is now intended for, then the Architect, Building Control, the Fire and Rescue Service, the Builders and Installers, the Fire Safety Manager (Building Safety Manager), the Fire Risk Assessor and the Residents should all be able to contribute to the fire safety of the building once refurbished.”
In other words, a virtuous circle of informed decision-makers is required.
BRE summarises standards
In addition, to amplify our understanding of the technical and regulatory issues arising from this overview of ‘adaptive reuse’, we value these views from the BRE (Building Research Establishment) whose notes summarise current thinking… including the interpretation of ‘stay-put’ policies that can result from compartmentation.
- Building Regulations 2010 (as amended): These regulations define the changes in use under Regulation 5 and set out what is required under regulation 6 – the ‘no worse than before’ principle, described in regulation 4(3), cannot be used when considering changes of use as buildings (parts of buildings) need to be brought up to standard.
- Compartmentation and ‘Stay-put’ (Building Regulations): In BRE Global’s opinion, it is not possible to take a ‘section’ of B3 (Internal fire spread – structure) compartmentation or a principle from B1 (Means of warning and escape) stay-put in isolation to give meaningful advice. A well-conceived change-of-use fire strategy will consider how all the interrelating parts of the Schedule 1 Relevant requirements B1 through to B5 have been complied with. Every case will have its own nuances and every case will need to be considered on its merits.
- Building and Planning controls: In BRE Global’s opinion, the fire safety professional should check the legality of the conversion, i.e., whether a formal building regulations application was lodged and that a statutory consultation between the Authority having jurisdiction (Local Authority or Approved Inspector) and the Fire and Rescue Service (FRS) was satisfactorily concluded and a Completion/Final Certificate was issued.
If the works are illegal, they will need to be regularised by the Local Authority under regulation 18 (Unauthorised building work).
- Note: Town Planning rules changed in May 2013 to allow office conversions to flats under Permitted Development, however it is still important to check whether the local authority had removed those permitted development rights (by an Article 4 direction) or if some aspect of the building work would have triggered the need to make a Town Planning Application.
- Building Regulation conclusions: In BRE Global’s opinion, having considered the plans, specification(s), status of the works (whether legal or illegal) the Fire Safety professional should also consider all the Regulation 38 (Fire safety information) arising from the change of use. This fire safety information should evidence design/inspection/validation by competent professionals. Finally, on considering all this background information and having conducted site visits to arrive at one’s own conclusions, regarding the change of use, the Fire Safety professional should then be in a position to advise the client on whatever aspect of fire safety they have technical competency to advise on.
Adaptive reuse… conflicts of interest?
According to the ‘mission statement’ of a leading multinational group of developers, there is ‘compelling evidence that adaptive reuse projects can deliver substantial benefits for developers and landlords’ with potential 10-75% lower costs than demolition and rebuild. And properties can be 15-70% faster to bring back to the market.
However, absent from these selective beneficiaries of ‘adaptive reuse’ is another all-important category . . . the occupants of the developer’s conversions. So, in conclusion, risk managers are urged to keep in mind the very real hazards of overcrowding that potentially could be an outcome for residents of ‘Mercantile-to-Abode’ apartments, as unwilling subjects of the law of unintended consequences.