These are buildings that were built:
- to a unique design by a local or locally important architect;
- before 1840 and survive in anything like their original condition;
- between 1840 and 1919 (that is, Victorian or Edwardian) and which -
- retain many of their original features; and
- are of sufficient quality to distinguish them from other buildings of the same period in the District;
- between 1919 and 1939 and:
- are a good example of the style of the period, or
- are an example of a particular building type that became more popular in the period;
- between 1939 and 1945 and are rare surviving examples of a wartime structure; or
- between 1946 and 1977 and are buildings of exceptional quality and design.