Paul Williams takes us through some of the challenges involved in refurbishing Manchester Town Hall and adding fire safety features
MANCHESTER TOWN Hall is a Victorian, neo Gothic building and the ceremonial headquarters of Manchester City Council. Designed by architect Alfred Waterhouse, the now Grade I listed town hall was completed in 1877 and turned 140 years old last year. While it has been maintained over the years and remains structurally sound, it is now seriously showing its age, with many elements reaching the end of their natural lifespans.
Without significant work to address damage and defects, its condition will deteriorate to the point where it will become unfit for ongoing use and would need to be ‘mothballed’. Sir Richard Leese, leader of Manchester City Council, stated: ‘Manchester Town Hall is a Grade I listed landmark of international significance which is highly regarded for its exceptional craftsmanship and architectural quality.
‘It is cherished by the people of Manchester having been the civic, political and administrative centre of the city since it was opened in 1877. Located in the heart of Manchester, it is the focus of the civic complex which is framed by two of Manchester’s most significant public spaces; the Grade 1 listed Albert Square to the west and St. Peter’s Square. For over 140 years the building has been central to the governance of Manchester, and is a valued heritage asset with significant levels of ceremonial, municipal and commercial uses.
‘Recognising its importance to the City, the Council made the historic decision to commit to the refurbishment and partial restoration of Manchester Town Hall and Albert Square, a decision that will see this jewel in our civic crown updated and made fit for purpose for another 140 years serving the people and the city of Manchester.’
There are many facets of the building that need refurbishment and restoration but, as it was designed in the 1860s, one of the more critical aspects is work needed to bring the building up to modern access and safety standards. Heritage buildings present unique challenges as regards fire safety and Manchester Town Hall is no exception.
Although there are some references to ‘fire proof construction’ in the original design documentation, the hall and historic buildings in general typically have few inherent fire safety features and often their current use will not be as was originally intended. Also, as is the case with many heritage buildings, there is also a drive to enable greater public use of the building.
Manchester Town Hall will seek to enable public events such as civic ceremonies, weddings, exhibitions and guided tours, while also providing open public access to all entrances and through the lower levels. In addition to the life safety risks to building occupants (staff and visitors), it is important to consider property and asset protection goals in the design. Within the context of Manchester Town Hall, this focuses on three main areas:
- The building – Manchester Town Hall is a Grade I listed building, which represents a key asset to the city of Manchester and could not be replaced.
- Assets on public display – assets including both portable and non portable items will be located around the building and in specific exhibition spaces. In all instances, an understanding of the value of the assets and specific areas where portable assets may be located need accounting for within the fire engineering design.
- Storage of portable assets – where assets are stored temporarily or permanently in the building, minimum provisions for their protection from fire need to be considered in the context of the value of the assets to be stored.
Returning to the life safety strategy for the building, this article will now focus on the proposed fire safety systems and features for the redevelopment, against the backdrop of the existing heritage provisions.
Means of escape
Means of escape provisions for the hall are still substantially based on the original fire strategy, comprising open stairs connecting all nine levels. This is at odds with current expectations for fire rated escape routes at such heights and, indeed for this reason, prior to the closure earlier this year to facilitate redevelopments, a substantial number of restrictions were in place relating to use.
One of the main drivers for the redevelopment is inclusive accessible access to all parts of the building. In achieving this, step free access is being provided at the main entrances with onward lift access to all floors. This provided a great opportunity to combine modern accessible provisions with modern egress provisions.
The proposed fire engineering strategy is therefore to provide a complete overhaul to the provisions for means of escape, and in doing so, provide four new fire rated escape stairs interwoven with the fabric of the existing building. These four protected escape routes will also double as firefighting access routes, with three being full firefighting shafts (incorporating a fire rated stair, firefighting lift and protected lobby), whilst the fourth is a lobby protected stair due to building constraints, making lift provision in this location impractical.
This coordinated design approach – which tackles both accessibility and fire safety issues simultaneously – results in substantially improved means of escape, whilst firefighting access facilities are also measurably improved. The main challenge in the integration of these protected routes within the existing building is focused on the interface at each level.
In new buildings, the footprint of each floor, layout of each floor and core design are generally uniform through the height of the building. But as a result of the different floor layouts in Manchester Town Hall, the layout of each protected route cannot be the same at every level. The design of each core is also bespoke for each level, which requires substantial coordination to enable the existing building to meet modern day requirements for fire rated egress routes and firefighting shafts.
Preventing a fire from occurring is a key element in the protection of both property and life safety. In many heritage buildings, the fire risk is commonly associated with old utilities, electrical wiring and plant. At Manchester Town Hall, a number of the more recent fire events have had similar origins, including small fires starting in old light fittings.
A substantial part of the proposed refurbishment is focused on a complete overhaul of the building services. By bringing these services up to modern standards, the risk of fire through faulty components or wiring is reduced and provides an added benefit – the opportunity to install new fire safety systems.
In order to provide an adequate level of life safety to the public and staff, a number of active fire safety systems are proposed for Manchester Town Hall, including a new fire detection and alarm system, new emergency lighting and escape route signage, and new smoke ventilation. Integrating these systems into the existing fabric of the building remains a challenge and it is not likely that a ‘one size fits all’ approach will be appropriate.
The proposed detection system is expected to be a combination of point type detectors, aspirating systems and beam detection – the last two being used where there are particularly sensitive heritage spaces, or in large public spaces such as the central Great Hall. The system will operate on what is commonly referred to as a ‘double knock’, the main benefit of which is that if there is an erroneous detection, the system does not automatically sound an alarm resulting in the evacuation of a few thousand people. Instead, it provides a period for investigation during which, if an incident is confirmed – either manually by staff or automatically through activation of a second detector – the alarm will be sounded. If the investigation concludes an erroneous detection, the alarm sequence can be cancelled, minimising the disruption to the large number of staff and public within the building.
A new fire alarm system is proposed for Manchester Town Hall which will provide an audible alarm throughout the building, in addition to visual alerting beacons in accessible facilities and anywhere where lone working may occur. There are many merits in using a voice alarm system for the audible alarm in a public building. These include not only the ability to broadcast different messages, as appropriate to the emergency, but also to decrease the overall evacuation time by encouraging people to begin to evacuate sooner than is typically experienced with a standard tonal alarm.
Conversely, designing a voice alarm system to suit the existing town hall presents many intelligibility and audibility challenges, that arise due to large open spaces and sound reflective surfaces, as is commonly experienced in rail stations and airports. This reverberation of sound around the town hall is likely to limit the intelligibility of the voice alarm message, to the extent that the benefit gained over a standard tonal alarm is lost. To continue the provision of varied messaging to occupants in the event of an emergency, a number of alternative systems are also being explored including active signage and variable signage using TV screens or room information screens.
In the future, it is quite likely that building management systems will be able to provide emergency information directly to occupants’ phones. In non public buildings, this is relatively straightforward to implement, as occupants are regularly present in the building, and staff inductions and fire drills can be used to administer a mobile based messaging system.
For public buildings, this form of messaging is more likely to piggyback off public information apps for the building. In the context of public buildings, it could be using information apps to navigate through an airport, or for heritage buildings, apps designed to help the public interact with the history around them.
Emergency messaging coverage through mobile technology cannot, however, be guaranteed in a public building, due either to individuals not having a suitable mobile device or choosing not to subscribe to the service. For a number of people, however, it can act as a useful source of ancillary information.
When fire occurs
Although fire prevention is always the starting point of fire safety, in the event of a fire starting it is important to either suppress or contain it to the smallest area possible. Within Manchester Town Hall the integration of a sprinkler system conflicts substantially with the heritage fabric of the building.
In the event of a fire occurring, the focus is therefore to minimise fire and smoke spread to the greatest extent possible. This is both to minimise the impact on the building and its assets, and to minimise the risk to life safety. Although the original design of Manchester Town Hall incorporates open spiral stairs between all floors, the primary construction is blockwork, which allows fire compartmentation around rooms or collections of rooms to be quite easily achieved.
Doors are the weak point in this strategy. The existing heritage doors are a varied collection of timber doors consisting of panelling and often also elements of glazing. Above many of the doors a ventilation panel can be found that is part of the existing ventilation to each room, ensuring a flow of air between rooms and the central corridors.
As part of the refurbishment, a condition survey will be carried out to determine whether retained doors will achieve an adequate fire resistance. Adequate in this context is unlikely to be analogous to the fire resistance rating that modern standards expect. An assessment of the performance of the doors will therefore need to be undertaken, and doors upgraded as much as is reasonably practicable, without impacting on their heritage significance. At this stage, these upgrades are likely to include minor interventions such as installation of smoke seals at frames, and self closers to doors and over door panels.
Some way to go
Manchester Town Hall closed to the public in early 2018 and will remain closed for refurbishment until 2024. In developing the fire safety strategy for this historic public building, there is still a long way to go and many challenges to overcome. There are of course the challenges associated with maintaining and protecting a heritage structure, but also the challenges of enabling safe public access to an important building, and to enable future generations to explore and appreciate this valuable Manchester asset .
Paul Williams is associate director of fire engineering at Arup. For more information, view page 5