Originally built in 1669, Bishop Cosin’s Library is one of the earliest public libraries in the North East of England, housing significant collections, and was granted "Designated status" in 2005, identifying the library and collections as being of national and international importance. The library has been run by Durham University since 1832, with further buildings being added during the Victorian period and in 1966, resulting in the set of buildings now known as Palace Green Library. The library came with many challenges, but with the support and guidance of our in-house specialist Conservation and Heritage Team, we successfully completed the conservation of the Grade II* listed library, using sympathetic materials and methods to ensure the history of the building is preserved. The works to Bishop Cosin’s Library are the latest in a complex series of phased renovation and regeneration works to the Palace Green Library site which involved the removal of the majority of the roof in order to correct the ingress of water to the library in order to protect the interiors and priceless collections from damage. The conservation and regeneration of the project has enabled the library and its collections to be more accessible and enjoyable than ever before. In addition to this, the reopening of Bishop Cosin’s Library to the public has created a deeper and richer experience for local audiences, visitors to the World Heritage Site, and beyond. We were appointed to provide Architectural, Principal Designer and Conservation services for this scheme.