The character of many urban environments in Scotland and throughout theUnited Kingdom Is being significantly altered by the large scale cleaning ofbuilding facades. The cleaning of buildings is being instigated by both pri-vate and public agencies and is carried out by a number of building contrac-tors. These contractors employ a range of chemical and physical means toremove dirt and staining from stone buildings. The cleanin of buildings raises questions at a number of levels. At the phys-ical level different methods of cleaning result in changes to the texture, co-lour, physical structure, and final appearance of the stone. Some techniquesfor the removal of dirt can result in the loss of architectural detail due tothe removal of stone particles as well as uncovering previously hidden de-fects in the stonework such as staining, biological growth etc. The subse-quent effects of weathering on cleaned buildings can also be unpredictable.At a physical level the decision to clean involves consideration of a numberof technical factors, evidence suggests however that some clients base deci-sions as to whether to clean buildings and on the method of cleaning on main-ly economic rather than technical grounds. At an aesthetic level the cleaning of buildings has implications for the way inwhich buildings are perceived. Deposits of dirt may hide the original inten-tions of the architect in relation to shadow, light, color etc. Converselylight deposits of dirt may enhance the shadowing effect particularly in atemperate climate and thus add to the buildings visual appeal. In additionmost buildings which are cleaned are one element of an urban group, thecleaning of one building needs to be considered in and overall architecturalcontext. Evience from urban environments in Scotland suggest that manybuilding groups in the urban landscape originally planned to be seen as asingle entity now due to different cleaning methods which result in varia-tions of stone colour after cleaning loose this unity. Once the decision toclean a building has made been questions arise as to what is the appropriatelevel of cleansiness to be achieved. Should buildings built 200 years ago beas clean as recently consructed buildings? Does leaving some dirt on thebuilding help add to the percepion of the age of the building or does the re-moval of any deposits of din tend to destroy its character? At the psychological level the preferences of residents in urban environ-ments regarding changes brought about by stonecleaning has received rela-tively little attention. To what extent is surface texture of buildings impor-tant in the cognitive schemes of individuals? The changes in perceptualevaluations brought about by the cleaning of buildings in relation to the cul-tural and historic significance of and area are issues to be considered beforea building is cleaned. The motives and perceived benefits/drawbacks forundertaking stonecleaning may vary between clients, archtiecs, contractorsan the residents of and urban area. The present paper will report results from the stonecleaning research pro-ject at Scott Sutherland school of architecture into the physical, psychologi-cal and aesthetic effects of the cleaning of building facades in Scotland.