Despite an unprecedented and extended investigative process, sufficient evidence to support any credible origin and cause hypothesis has not been recovered from the scene or evidenced in witness testimonies or eyewitness accounts.

Therefore, the origin and cause of the fire incident at the Mackintosh Building on the 15 June 2018 has been recorded as “undetermined”.

It has been a long wait for this report, and it is disappointing that after three and a half years, we are still no nearer finding the cause of this devastating fire to the Mackintosh Building. Here are some key points from the report:

Unfortunately, almost everything within the building was severely damaged or consumed in the fire and that included any potential items of evidence that could have provided those answers.

• They believe the fire began on the east side of the building on or above level four.
• The building had been subject to extensive construction work for almost two years. Electrical, plumbing, heating and data services were in the process of being installed throughout the building. Large quantities of combustible materials had been either fitted or were stored throughout the building waiting to be installed.
• Despite doors to rooms and cross corridor doors being in position, the doors that were in place, whether original or temporary, would be unlikely to be capable of demonstrating fire resistance in the same way as a modern “rated” British Standard (BS476) fire door set would.
• Some of the original doors remained in their original locations, with some temporary doors fitted where original doors had been removed for refurbishment.
• Passive fire safety measures were compromised across the entire building due to the nature and extent of the refurbishment work being carried out. This level of vulnerability during construction is not uncommon, however it does significantly increase the risk of fire spread where the fabric of a building has been compromised.
• Active fire safety measures should have been subject to a thorough programme of scheduled maintenance and testing.
• It was confirmed by the main contractor that onsite records for testing and maintenance of the FWS were only retained on site and were consumed in the fire. The Mackintosh Building has an additional inherent design feature that further compromised the passive fire safety measures and contributed further to the increased risk – ventilation ducts.
• The original Mackintosh designed ventilation system featured ducts throughout the entire building. The network of ventilation ducts varied in construction type, but have been observed as being brick, metal or timber lined. The legacy ventilation system was referenced in the 2014 fire report as a major contributor to rapid spread of fire.
• The report also found that ‘uncontrolled fire growth and rapid development’ of the fire – half of the building was ‘well alight’ within 38 minutes of the arrival of firefighters – had been fuelled by the unlimited air supply drawn through ‘exposed and unprotected’ ventiliation ducts.
• As a result of the refurbishment work undertaken prior to the 2018 fire, the original ventilation system played an even greater role in supporting smoke, heat and fire spread. Many of the ventilation ducts were exposed and unprotected to allow services to be channelled throughout the building (electricity/data/heating/ plumbing).
• The ducts had no effective passive fire stopping measures or cavity barriers although, fire dampers had been fitted to some areas but were not operational. The remainder of the ducts were scheduled to be fitted with fire cavity barriers/fire stopping measures upon completion of the installation of services.
• At the time of the fire, these active fire safety measures were not commissioned or fitted, providing a route for fire and fire gases to rapidly spread both horizontally and vertically. The well-ventilated ducts most likely served to provide a chimney effect, entraining an endless supply of fresh air to the fire as it developed and spread across the entire building.
• Although the fire service could not pinpoint a possible origin, the investigation team did come up with a number of possible hypotheses which could not be discounted.

1. Arson, potentially by ‘a lone figure in the car park’ caught on CCTV cameras three hours after the discovery of the fire
2. Fault or failure of electrical appliances or distribution systems, including supply cables, transformers, 110volt trailing leads and festoon lighting as a potential ignition source
3. Non-electrical accidental ignition, such as by a smoker of a chemical reaction inducing spontaneous combustion linked to a sander.

Due to the extensive damage throughout the entire site, post fire indicators were not available to support the investigation by indication of a possible origin or cause area. Directional indicators did not exist on the remaining structure as surface finishes had either spalled or been consumed in the fire, window lintel blackening, although visible, was present on multiple apertures as the fire progressed through the building. To competently determine the origin and cause of this fire, the hypotheses offered above have been tested against the evidence available to the FIO. Despite a sustained, comprehensive investigation and excavation process, carried out over a three-year period, SFRS where unable to identify any evidence that would competently test and support the hypotheses. Having, considered the available evidence and the possible origin and cause hypotheses, in the absence of any further information, I conclude that the cause of the fire to be recorded as Undetermined. Should further information be presented, this will be considered, and the conclusion of this report may be subject to a comprehensive review. Peter Allardice – SFRS

The full report is available here GSA Fire Report 25jan22