The seven-storey building just south of Edinburgh city centre was constructed in two phases in 1989 and 1995 for £50m and is now suffering from leaks.

The library’s owners said: “All of the major elements of the external envelope (including the roof, rain screen cladding, glazing, stonework and water discharge systems) are exhibiting significant defects, due to the compound effect of deteriorating materials, poor workmanship and complexity of design.

“These failures have led to widespread air and water leakage.”

They are now looking for a contractor to replace the building’s external envelope to protect the National Collection housed inside.

Up to five firms will be shortlisted for the job and contractors must express their interest by August 28 with National Library of Scotland George IV Bridge C/o Estates Division Martin Sinclair EH1 1EW Edinburgh UNITED KINGDOM +44 1312402600 [email protected] Internet address(es): General address of the contracting authority: www.nls.uk Address of the buyer profile: www.publiccontractsscotland.gov.uk/search/Search_AuthProfile.aspx?ID=AA11622