Heritage Oudtshoorn Erfenis Guidelines Some guidelines when making changes: For all buildings > 60 years Additions mustbe sympathetic to the existing building.not negatively impact on the streetscape.not alter the character of the original building.A second structure should not dominate the original building. Tips for Additions to Heritage Buildings Set the second building back from the original building. Design a second dwelling as something totally different to the original building with a link to the existing structure.