An architect-led multi-disciplinary design team is now being sought to realise the restoration and an appointment is to be made in early 2015.
The category A listed building was designed by Charles Rennie Mackintosh and completed in two phases in 1899 and 1909.
The 1899 part of the building, which includes the Mackintosh Museum, Mackintosh Room and Furniture Gallery was saved from the blaze and the GSA Archives have also escaped damage.
However the 1909 part of the building, which includes the library, was badly damaged.
Murial Gray, chairwoman of GSA gives an assessment of the damage here, which wasn’t as bad as first feared – 90 per cent of the building’s structure and 70 per cent of its contents were saved.
The GSA says it is ‘wholly committed to reconstructing and restoring the Mackintosh Building to its full use as a working school of art and its architectural glory.
‘In delivering this goal we have the backing of Government agencies at national and local levels and the support of benefactors from around the world.’
£20 million is being sought to fund the restoration and so far £6.5 million has been raised, which includes £5 million from the UK Government and a pledge by the Scottish Government (which has donated £750,000 so far) and will match fund any money raised by GSA up to £5 million.
A GSA spokeswoman says the university is still waiting on a fire report from the fire services to determine the cause of the blaze.