Glasgow School of Art (GSA) had gone to extreme lengths to restore the Mackintosh building after the 2014 fire.
The school described itself as “custodians of an iconic piece of world architectural heritage” with a responsibility to restore it for students and staff.
The blaze caused significant damage to the west wing, including the loss of the celebrated Mackintosh Library, and the first stage of the restoration was to fit a temporary roof over the site.
A full-scale model of part of the library was later built to test if the original materials and techniques from Mackintosh’s 19th century design could be used in its reconstruction.
The specifications for the model bay were developed with “meticulous research” into every aspect of the original design and construction of the library held in the GSA archives and the original drawings in the Hunterian Museum.
To rebuild the wooden library, the restoration team sourced wood from the US which was the same age as that used in Mackintosh’s 19th century design.
Keir Construction were managing the project with the design led by Page\Park Architects.
The first phase saw outer work with damaged stonework repaired and the roof replaced before the delicate process of restoring the west wing and upgrading the east wing interiors began last year.
Work was due to be completed in February 2019.
Glasgow MP Paul Sweeney described it as “the most architecturally important building in Glasgow”.
He tweeted: “The Mack restoration project, led by @pagepark and others, has been an incredibly innovative effort to restore Mackintosh’s masterpiece to life.
“I can only hope that the skills developed on it since 2014 will help to overcome this horrific setback. We cannot lose this building.
“The 2014 fire destroyed around 20% of the western wing of the building – a later extension completed in 1909, containing the spectacular library – with a further 30% smoke damaged. This fire appears to be much more extensive and affects the 1899 eastern wing of the building.”
Donations for the £32 million restoration flooded in from around the world.
Both Scottish and UK Governments supported the rebuild, while artists, celebrities and former students made significant donations.
Hollywood star Brad Pitt and Dr Who actor Peter Capaldi were made trustees of The Mackintosh Appeal to support the rebuild.
Pitt is a fan of building designer Charles Rennie Mackintosh and Capaldi is a former art school student.
Leading artists including Sir Antony Gormley, Anish Kapoor and Simon Starling used material from the fire-damaged art school to create new work that was auctioned to raise funds.
A total of 25 international artists were sent material retrieved from the Mackintosh library with Grayson Perry, The Chapman Brothers and Sir Peter Blake also contributing to the project which raised £700,000.
The Prince of Wales showed his support for the restoration with a visit to the Mackintosh building in 2015.