The £51m restoration of the Mackintosh Building in Glasgow is to return to the ideas of its world-famous architect.

The design team behind the restoration of the Glasgow School of Arts (GSA) landmark building is to return its famed library - destroyed in the disastrous 2014 fire - to Charles Rennie Mackintosh's original design.

The new library will look, the team hope, as it did in 1910.

The Herald:

Site manager Philip Munro of Taylor Fraser pictured in the destroyed Mackintosh library at the Glasgow School of Art. Photograph by Colin Mearns

That will be a different look from the room that many will remember from before the fire - it will lack the accretions added over the years, including darker wood, the staircase to a mezzanine, and many extra bookcases.

The design team of the Restoration Project, led by Page/Park architects, have instead decided to build the new library from scratch and based on Mackintosh's original plans, albeit with some "concessions to modernity".

Furniture based on the original will be commissioned, and its lamps both restored and remade.

The library will be rebuilt largely in American tulipwood, as it was in 1909/10, with some Douglas Fir.

Sarah MacKinnon, project manager of the Mackintosh Restoration Project, said: "The design team have looked at huge amounts of information from our archives, from the Hunterian, from all over the place.

"And with them, we have designed that Mackintosh's influence on this room [the library] ended in about 1913.

"And if we are going to put it back, we should put it back to where he intended it to be, so are putting it back to its 1910 configuration.

"So there will be no staircase, the bookshelves will be in a 1910 style - it got more and more through time. It will be slightly sparser than it was."

Ms MacKinnon spoke as she guided The Herald around the building, which is heading into its most important stage of restoration.

Contractors for the revamp will be chosen in June and will be onsite in July.

"Mackintosh didn't build this library, he designed it, and we can to a huge extent understand the design from the records we have," Ms MacKinnon added.

"We are putting a new library in here, it would be ludicrous if it looked old - it would be dishonest if it looked old."

There will be more plug sockets, improved WiFi and underfloor heating.

This week its many classical and medieval plaster casts will begin a process of storage and restoration: of the 224 in the building, 4 were destroyed and 12 badly damaged, others were blackened by soot.

The Herald:

Conservator Graciela Ainsworth, in foreground, working on a damaged cast of the statue 'Dying Slave' by Michelangelo. Photograph by Colin Mearns

The plaster on many surviving casts has become brittle and are now being restored by conservator Graciela Ainsworth of Edinburgh and her team.

Ms Mackinnon added: "The library will be substantially constructed in exactly the way it was.

"One or two structural things that will be improved - for example, the balcony was a bit shoogly on one side, and the biggest difficulty is the finish of the timber.

"We don't exactly know what it was in 1910, there is nothing surviving that can give us that evidence.

"It was a very dark room, but there is a strong belief that it wouldn't be as black - because it got dirtier, it was over-painted, there was pollution, cigarettes and so on."

David Mullane, chair of the Friends of the GSA, had been dubious about the merits of restoring the library, but said: "With the work in the hands of Page/Park there is a good chance that full restoration will be relatively successful.

"CRM is not around, neither are the experienced tradesmen of 1910.

"Even the wood will be different and more than 100 years of patination will be missing from what we remember.

"But David Page is a sensitive soul, for whom I have a lot of respect. He has told me that he believes that full restoration is the way forward."

The total cost of restoring and upgrading the Mackintosh Building is around £51m.

The GSA will meet this cost from its own resources, including insurance settlement, disposal of buildings no longer "fit for purpose" - the JD Kelly and Richmond Buildings - and fundraising.

Around £17m has been raised to date, including £15m from the UK and Scottish governments and £2m from philanthropic giving.