This International Standard provides general requirements and procedures for the assessment of existing structures (buildings, bridges, industrial structures, etc.) based on the principles of structural reliability and consequences of failure. It is based on ISO 2394. It is applicable to the assessment of any type of existing structure that was originally designed, analysed and specified based on accepted engineering principles and/or design rules, as well as structures constructed on the basis of good workmanship, historic experience and accepted professional practice. The assessment can be initiated under the following circumstances: - an anticipated change in use or extension of design working life; - a reliability check (e.g. for earthquakes, increased traffic actions) as required by authorities, insurance companies, owners, etc.; - structural deterioration due to time-dependent actions (e.g. corrosion, fatigue); - structural damage by accidental actions (see ISO 2394). This International Standard is also applicable to heritage structures provided additional considerations shown in Annex I are taken into account. This International Standard is applicable to existing structures of any material, although specific adaptation can be required depending on the type of material, such as concrete, steel, timber, masonry, etc. This International Standard provides principles regarding actions and environmental influences. Further detailed considerations are necessary for accidental actions such as fire and earthquake. NOTE Fire resistance requires properties different from those for structural safety and integrity. Also fire hazards can be created by change in use. Special requirements are necessary for seismic hazards taking the dynamic action and structural response into account.