THE restoration work to Glasgow of School Art after the 2014 fire was not subject to the usual building regulation and inspection procedures.

Nine days ago a second fire ravaged the building raising doubts that "the Mack" can be saved. Normally approval has to be given for any building or alteration and building control warrants are a requirement, together with mandatory site inspections carried out by city council experts. This did not happen.

The Sunday Herald can now reveal that because it was a Grade A listed building it was exempt from the process and the work was not vetted or inspected by Glasgow City Council officials. Like-for-like replacement – virtually all of the Mack refurbishment – is exempt.

Officials did inspect a "small number of improvement works" – such as the sprinkler and fire detection systems, which were installed but not commissioned, ventilation and toilets – which were subject to vetting and building control.

A Glasgow council spokesman said: “As this was very much a heritage-led restoration (as directed by Historic Environment Scotland), with much of the material being reinstated on a like-for-like basis, building warrants were not required for many aspects of the project."

According to one leading fire safety expert consulted on the project, insulation materials used in the refurbishment were of the same type used in Grenfell Tower.

The art school refused to confirm or deny this in a series of questions put to them and have banned staff, contractor and the architects from speaking to the media.

There is no suggestion that the insulation was the cause of the original fire but it might explain why it spread so quickly and fiercely as these are combustible materials. Firefighters who arrived at the scene within minutes were stunned by the severity of the blaze and the speed with which it spread. One described it as being like a "firebomb".

The council spokesman confirmed that further inspections of the improvements would have been carried out with certification issued on completion of the building. Ironically it was Glasgow's building control experts who revealed during the week that the building had moved six inches, with council leader Susan Aitken warning that "the building may collapse. If that were to happen it could happen with no warning."

According to the senior source consulted on the Mack restoration project the insulation used was 100mm PIR (the acronym for polyisocyanurate) on a breathable polyethelene membrane. The GSA refused to comment.

This kind of insulation is considerably cheaper – up to 50 per cent – than non-combustible mineral fibre brands like Rockwool panelling which is composed of strands of stone.

The Sunday Herald asked Kier, the construction company carrying out the renovation for the GSA, what insulation materials were used. Kier reiterated a previous statement that "an agreed fire safety strategy was implemented" and referred questions to the GSA.

Architects Page\Park also refused to answer and referred all questions back to the GSA.

As we reveal elsewhere the art school have instituted a policy of blocking media inquiries over the fire. There has been no statement from them since the chair of the board of governors, Muriel Gray, said five days ago that "the world's most indestructible building" can be restored from the ashes of the present. She also said that construction firm Kier had "questions to answer" over the fire.

This was before Glasgow's building control discovered that the building had moved significantly and was in danger of collapse. Estimates have put a complete rebuild and restoration of the building at in excess of £100 million.

The restoration which went up in flames was scheduled to cost around £35m, the bulk of it public money. Both the Scottish and UK Governments supported the rebuild while artists, celebrities – like Hollywood star Brad Pitt and Dr Who actor Peter Capaldi – and students also contributed.

The previous fire, in 2014, occurred when a student brought in a can of expanding foam, which was banned from the building, and the fumes from it came into contact with a projector which had been on for three hours and then ignited. That blaze caused severe damage to the west wing of the building – including its jewel, the Mackintosh library – the second fire completely devastated the whole building.