The Mitchell Library is set to undergo repair work to tackle subsidence as the ground below it has been sinking.
Cracks were discovered in the Jeffrey Room, and part of the building façade is now lopsided compared to the rest.
Experts have found the subsidence is confined to the footprint of the Jeffrey Room and estimate the issues may have started more than 100 years ago.
Glasgow Life has applied for building listed consent to carry out internal and external work to the library, which is one of the biggest in Europe and has been located on North Street since 1911.
Options have been put forward to stabilise the property.
The contents of the Jeffrey Room were moved out in 2018 after the problems first came to light.
An architect’s report said: “In 2017 cracks in internal walls, floors and ceilings became evident inside stairwell 13, The Jeffrey Room and other interior spaces located in the southern bay of the Mitchell Library’s 1911 wing, on all four floor levels adjacent to the external wall at Kent Road.”
The report said: “The Kent Road façade has dropped vertically by approximately 24mm (2.2 centimetres) relative to the rest of the building.”
The report said that change was “due to the slow, very gradual migration via the water table of extremely fine soil particles being leached from the ground below the foundations, into the surrounding soil strata, underground drainage system, and the interior of the rail tunnel.”
It added: “This process may have commenced very soon after completion of the original library, 111 years ago, and appears to be exacerbated by heavy downpours. It is possible that damaged drainage pipework may also be a contributing factor.”
Work is to include stabilising the masonry façade, repairs to the local underground drainage system and the library building’s above-ground drainage system among others.
A contractor is to be appointed after a tendering process but planning documents have not stated a timeframe for the work.
The planning application is listed as pending consideration.