The planners cannot go out today from a tabula rasa situation anymore. Environmental and sustainability issues have already formed the public idea that a 'greenbelt' of our cities is necessary, a kind of fortification leading to intensive development in towns inside a clearly delimited area within the surrounding nature. Since building on the periphery is limited, and the existing built substance has a certain cultural, architectural or at least environmental value, upgrading of existing buildings gains more and more ground from the design of new buildings. Masonry has been already recognised as construction material par excellence for historic structures. Reinforced concrete has not been yet. The reason for this may lay in the fact that concrete has not been employed for long, thus buildings with concrete structure are generally regarded as not old enoughto be considered historical. But the International Council on Monuments and Sites at a joined seminar with UNESCO and the International Centre for the Study of the Preservation and Restoration of Cultural Property in 1995 in Helsinki deemed the systematic documentation of the 20th century heritage, when these buildings were raised. The book includes chapters on these components of the building stock which have not been covered by previous studies, with architectural or cultural value. Special attention was given to a recommendation of the ICOMOS seminar in Helsinki, which concerns encouraging research programmes on specific problems concerning techniques and materials in restoration work, taking into consideration their aesthetic qualities. ICOMOS members are authoring
