The human interventions transform a part of the natural environment in built environment, formed by buildings of different types: edifices, works of art, technical-urban networks etc. The built environment is always offensive, while the natural environment is permanently retreating. When studying the phenomena, we inevitably meat with compatibility problems of interventions. This volume includes the programme and the materials of the 11^th edition of the Conference Series on Theoretical and Practical Issues on Built Heritage Conservation – TUSNAD, having as topic Built Heritage Conservation, Compatibility Issues.