PPS 6 Planning Archaeology and the Built Heritage·Page 26·Policy BH 8
Policy BH 8: Extension or Alteration of a Listed Building
The Department will grant consent to extensions or alterations of listed buildings only where the essential character and setting are retained, special interest features remain intact, traditional and sympathetic materials and techniques are used, and architectural details match or are in keeping with the building.
The Department will normally only grant consent to proposals for the extension or alteration of a listed building where all the following criteria are met:
(a) the essential character of the building and its setting are retained and its features of special interest remain intact and unimpaired;
(b) the works proposed make use of traditional and/or sympathetic building materials and techniques which match or are in keeping with those found on the building; and
(c) the architectural details (e.g. doors, gutters, windows) match or are in keeping with the building.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/PPS 6 - Planning Archaeology and the Built Heritage.pdf