3D images of fire-damaged Glasgow School of Art Mackintosh building

Glasgow School of Art has released 3D images of its fire-damaged Mackintosh building as it looks to appoint a main contractor for the restoration project.

Five firms have been shortlisted and invited to submit bids for the work. The winner will be appointed in June.

Work is scheduled to start on site shortly after the close of this year's degree show in June.

The iconic Grade A-listed art nouveau Mackintosh building was badly damaged by fire on 23 May 2014.

An investigation by the Scottish Fire and Rescue Service concluded the blaze was caused by flammable gases from a canister of expanding foam.

The report said the gases ignited as they came into contact with the hot surface of a projector in Studio 19.

Since the fire, Glasgow School of Art (GSA) has been involved in efforts to raise £20m towards the eventual cost of restoring the Mackintosh building and its contents.

In May last year, it was confirmed that Glasgow-based Page\Park Architects had been appointed to lead the restoration project.

GSA has now revealed that Balfour Beatty Civil Engineering Ltd, BAM Construction Ltd, John Graham Construction Ltd, Kier Construction and Sir Robert McAlpine Ltd, have all been shortlisted and invited to tender for the main contractor role.

Liz Davidson, senior restoration project manager, said: "Clearly we need a contractor who is able to deliver the full range of technical requirements for the retrofit and has a proven track record in bringing major restoration projects in on time and on budget.

"However, over and above this we are looking for the inclusion of experienced specialists who are capable of undertaking the expert restoration of this Category A Listed building.

"We are looking for our main contractor to have the appropriate expertise in their team to deliver to the highest standard in terms of the specialist skills."

Once the appointment is made, the removal of the stonework comprising the library window gable will be among the first jobs to be undertaken.

This will be followed by the reconstruction of roofs which were totally destroyed in the fire.

Final preparation work - the strip out of the fire damaged west wing - is currently underway and will be completed by the end of May.

GSA also released post fire 3D visualisations of the Mackintosh building, created by its Digital Design Studio

They will form the basis of a BIM (Building Information Model) which will document every stage of the restoration.

This will create a detailed record of the work undertaken for future use both by the GSA and other organisations carrying out complex restorations of historic buildings.