The landmark Mackintosh building at the Glasgow School of Art (GSA) will once again be rebuilt from the original designs of Charles Rennie Mackintosh, the institution’s chairwoman has confirmed, though the project could take four to seven years to complete.

The A-listed structure was reduced to a shell in June following a second fire in its 110-year history as a restoration project following the devastating fire four years earlier neared completion.

Muriel Gray confirmed that the building would again be restored using Charles Rennie Mackintosh’s original designs.

It has been estimated that the restoration could cost about £100 million, but Ms Gray said the school hoped to use minimal amounts of public money for the project and rely on funds from its insurance cover and a private fundraising drive.

She told The Herald on Sunday: “We are resolved that the Mackintosh comes back as a working art school, as a major player, a cultural leader for the city and the Scottish economy.”

“It is absolutely coming back. It will be beautiful. It will be as Mackintosh designed it, to the millimetre.”

Ms Gray added: “It can be rebuilt. The absolute genius of Mackintosh was his modernity. The modern technology now to do it is there, but not only that, this can be a huge project for our students and community, to be part of the rebuild, getting our own students involved in research projects as it goes up.”

Original plans from the Mackintosh Building, built in two stages between 1896 and 1909, are held in the GSA’s stores and at the Hunterian at the University of Glasgow, and the school also has digital BIM model from the restoration work following the 2014 fire.

Ms Gray said: “How long will a rebuild take? People argue anywhere between four and seven years.”

“That will depend on the insurance money, getting the right people in place to do it, building regulations, all the standard technical and financial stuff

“For the forensic detail we have on the building, we could practically 3D print it.”

Ms Gray said funding plans were being drawn up. “We are entirely trusting that this is not going to cost any public money at all,” she said. “We are hoping — because you don’t know what adjustments you have to make to conform to modern building standards — but that is our hope.”