The materials of roof-tiles are described and a short history of roof-tiles is given. Differences in production, properties and optical qualities between old and new ceramic-ware are discussed. Definitions of patina and the structure of old Austrian tiles are explained including a comparison of various types from the Roman period to the 18th century (data included) with some new products of Austria, Bavaria and Switzerland. Criteria for recommendations and tests of new ceramic tiles are discussed and the industrial standards used are criticized. Advantages and disadvantages of concrete-tiles are finally reviewed.