Case Study – Conversion of former railway arch into a restaurant and bar, Edinburgh
The project comprised the redevelopment of C-listed Victorian railway arches which dated back to 1875.
The design proposal was to fit out one of the arches to house a ground floor bar and dining mezzanine with a total occupancy capacity of up to 100 people including staff.
There was only one exit from the building. Building Regulations limit the maximum numbers within building where there is only one exit to a maximum of 60 people.
Appointment of Fire Risk Design Co.
Fire Risk Design Co. were appointed to provide a performance based fire safety solution to support the design and use of the premises. The design incorporated a mezzanine floor extending to more than 50% of the floor area and a single exit, the occupant capacity exceeded 60 persons.
The project presented the following challenges;
The restaurant featured a mezzanine that extended more than 50% of the floor area.
Building Standards Verifiers confirmed that the requirement for two escape stairs/fire exits could be varied on the basis that a fire suppression system be installed.
Building Standards Verifiers confirmed they would not allow an occupancy of more than 60 unless it could be demonstrated through a fire engineered approach that a higher occupancy would still allow adequate means of escape.
The installation of a suppression system (sprinklers) would require a pump and tank system.
Site constraints, costs (estimated £70,000) and planning restrictions prohibited the provision of a sprinkler system incorporating a pump and tank supply.
Fire Risk Design Co. developed a performance based design making use of the physical provisions of the site to ensure life safety, the design evaluation depended upon a time based comparison of the time available for occupants to escape to a place of safety.
Using this approach, it was possible to vary from the restrictions imposed by prescriptive rules (the number of available exits from the building).
This was achieved by designing a performance based fire safety solution demonstrating that the available safe evacuation time (ASET) exceeded the required safe evacuation time (RSET) by an appropriate margin of safety.
In creating a fire strategy for the premises, a holistic approach was taken. The building design had to provide a level of safety for its occupants, and a means of escape in the event of a fire.
Steps were taken to minimise the risk of fire spread. These were combined with the provision of sufficient facilities for the fire and rescue service to safely tackle a fire. It was of combination of all of these elements that determined the fire strategy.
Natural ventilation of the premises using an existing door and windows adapted to operate on activation of the fire alarm (manual break glass call points and automatic detection) provided a 59% margin of safety, for occupants escaping the mezzanine and a 68% margin of safety for occupants on the ground floor.
Building Standards Verifiers accepted the performance based solution that incorporated the proposed arrangement of windows and door on the front elevation configured to operate (open) on the actuation of the fire alarm system.
Acceptance of this solution negated the requirement for a second means of escape or the installation of an automatic sprinkler system.