By Karl Wallasch. Developers now acknowledge that people who don’t have office spaces to work in often crave the atmosphere of being around others. The real success is when co-working spaces don’t just bring people together, but also cater to people’s personal preferences.
An individual has the option to hang out in a communal space and bounce ideas off others, enjoy the quiet of a private room, or even sit and work on their own enjoying the background buzz of other people. It’s all about choice.
From architectural and heath & wellbeing considerations, to the need for customisation and flexibility of the space, there are key priorities when developing, designing and building new co-working environments.
The fire safety concept plays a key role in all of these, as well as achieving a safe and compliant buildings that causes minimal impact on architectural vision or management during use.
Fire safety challenges
The particular challenges that co-working spaces require from fire safety engineers are:
- The existing building: often co-working companies take over parts, or the whole of existing buildings. Sometimes these build -ings are already classified as offices or a change of use is required. Fire strategies for the co-working spaces have to be developed to achieve compliance with the functional requirements of the Building Regula-tions, while also considering constraints due to existing nature of the building, such as geometry, height, listed heritage, materials, stair and exit sizes, etc.
- Change-of-use requirements: Co-working brands often choose warehouses or listed heritage buildings as the location for their new space. If a change of use is applicable then all aspects of fire safety need to be considered i.e. means of escape, internal fire spread, external fire spread, firefighting access and facilities. Improvements are also likely to be needed for the existing building to comply with the latest fire safety guidance, even going as far as installing new fire safety systems (for example, automatic fire detection, smoke ventilation to basements, stairs and lobbies, sprinkler provision, and dry riser system). These new fire safety systems may influence the architectural design, as well as increasing plant room space and costs.
- Extending existing buildings: Extensions of existing building are common to increase lettable area. Historically, the height of an office building will dictate the level of fire resistance to structure, the provision of minimum fire safety systems, and the firefighting shaft requirements. Commercial buildings with a height of more than 18m require a firefighting shaft provision; and when greater than 30 m require sprinkler protection. When dealing with existing buildings, this can result in increased costs and plant requirement.
- Higher density of population: The nature of co-working business models requires a high density of working spaces.
Traditional guidance requires eight to 10 square metres for every one person, but within co-working spaces populations of six or even five square metres are common. While, in new buildings, these higher populations can be considered with additional or wider stairs, it can be challenging in existing buildings and BS 9999 often might be the more suitable solution when analysing occupancy levels. This is because BS 9999 takes into account a detailed risk profile, fire load, geometry of the building (for example ceiling height), and the fire safety systems in place. Therefore, higher occupancy figures can be achieved without undertaking physical changes to the existing building or introducing new stairs. However, another option is also feasible: fire engineering. The use of fire engineering principles (PD 7974, CIBSE Guide E) through either detailed hand calculations or modern modelling of evacuation and people flow (via existing exits and stairs) can demonstrate the maximum possible number of occupants for entire buildings or individual floors and overall escape times.
In some instances, by comparing evacuation times with fire and smoke simulations (which indicate the time it takes for conditions to become untenable), a margin of safety can be established.
- Single-stair buildings: In the UK, the maximum height of single-stair office buildings is 11 metres. This is historically linked to the height at which fire and rescue service personnel can rescue occupants using the standard 13.5 metre portable ladder. While this practice is no longer common, for health and safety reasons, fire-fighters continue to carry out external rescues as a last resort and building design should recognise this. Nevertheless, in recent years fire engineering approaches have allowed for single-stair buildings to exceed these heights and the industry is developing a new guidance for single-stair buildings that will be released soon.
- Approval for using fire engineering principles: Deviating from standard guidance and applying fire engineering tools requires intense discussions with the approving authorities, and may require a detailed QDR (Qualitative Design Review) process.
- Stairs that are difficult to rebuild or change: When dealing with an existing building, it’s important not only to analyse ‘width-from’ drawings, but also to undertake measurements of clear stair and exit width on site.
- Open stairs creating voids: Architectural concepts may include creating open voids or atria to link two or more levels. However, this can cause smoke and fire to spread unstopped between floors (internal fire spread), and changes the external fire spread assumptions, as more than one floor could create radiation to neighbouring buildings.
- Possible solutions may be vertical (instead of horizontal) compartmentation e.g. use of fire/smoke curtains, fire rated glazing, sprinkler protection, or a strategy that allows for larger compartment zones (a two-floor compartment instead of a single-floor compartment strategy).
- A welcoming reception area: Large open receptions form a key part of most co-working spaces’ architectural vision. Although they are the main entrance point to the building, they often can’t be part of the protected and sterile means of escape route. Therefore additional means of escape corridors may be required, connecting protected stairs directly with the outside. The same may be applicable for dedicated firefighting access routes that allow firefighters access to firefighting shafts directly from the outside.
- Defined purpose groups: While traditional offices were designed for one main purpose, the co-working environment is often made up of many individual or small-scale companies that share common space. There’s a demand for flexible meeting rooms, conference and events areas, along with social and leisure areas, plus connected café, bar and retail facilities that might be open to members of the public. This means any fire safety concept needs to consider the risk profile of each of these different-purpose spaces and their implications on the surrounding use. This is especially true if they are connected to each other e.g. a coffee bar for external visitors that is open to the office’s reception.
- Event spaces: Co-working spaces may include large event spaces used by co-workers as well as members of the public. This is often likely to result in an increased number of occupants in the building or on particular floors. Risk profiles need to be considered as not all occupants will be familiar with the building.
- Use of new materials and pushing boundaries for interiors: To create a vibrant, modern co-working environment, or to assert the brand identity of companies using the space, new interior materials are likely to be proposed. It’s essential to fully understand the fire performance and classification of each of these materials. A fire strategy concept developed for a base build may need further development to consider such fit-out specifics.
- Building management: When developing fire risk assessments, the safety strategy needs to be clearly communicated to building management teams. A record of all fire safety information is essential, as well as understanding the potential for future changes and associated risks. Bespoke fire safety strategies often need revisiting when significant changes take place.
Project Example: Eastgate House, London
Fire engineering techniques allowed for an innovative new co-working space at Eastgate House in London, located just north of Oxford Street. The brief was to transform the existing office into a modern space for co-working brand Fora ( www.foraspace.com ). The proposal by architects Hassell included an open reception, shared/common meeting rooms, and omitted the existing external stair to allow for greater floor spaces and easier people movement.
Fire engineering solutions for Eastgate House
Traditionally, a single-stair office building in England and Wales is limited to 11 metres in height. Eastgate House is 19 metres, which not only exceeds the height criteria but also goes above the 18-metre height mark for firefighting shaft requirements. In response, a full fire safety strategy concept was developed including an upgrade of the existing internal stair to a firefighting shaft and to justify the proposed single-stair office design concept. A detailed evacuation study was undertaken, analysing the time to fire detection, recognition, response and travel time for both horizontal and vertical escape (RSET). Computational Fluid Dynamics (CFD) modelling also allowed the ‘time to untenable conditions’ to be assessed (ASET), along with analysis of ‘worse case’ fire location.
The evacuation study also included assessment of potential fire load, fire size, soot yield, door-opening times, and smoke ventilation conditions. An example of smoke-spread analysis is included in Figure 7.
Ultimately, these modern fire engineering techniques meant the proposed single-stair arrangement met the functional requirements of Building Regulations and was shown to have an adequate level of safety (both as a means of escape and during firefighting).
This article discusses some of the trends in co-working office developments that could result in challenges for fire safety engineers. Often, current fire safety guidance may not fully address these challenges. However, modern fire-engineering techniques can be used as an alternative approach. This approach not only allows for compliance with the functional requirements of the Building Regulations, but also enables a better and more detailed understanding of design options, risks, and future flexibility in unique building situations. Ultimately, it means life safety, property protection, business continuity, and brand protection requirements can be fully considered and successfully delivered to allow for unique and exciting co-working spaces.
Karl Wallasch, Technical Director, Dipl.-Ing., CEng is a Fire Engineer working in Hoare Lea’s Fire Engineering team in London. Karl studied structural engineering at the Bauhaus University in Weimar, Germany. He has working experience in the UK, Europe and abroad.
The article was published in FeuerTrutz International, issue 1.2019 (January 2019).
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