In countries of European Union (EU 27 excluding Malta) are situated approximately 100,1 million multifamily dwelling units according to the Report for European Housing Ministers Conference held in Prague, 03. 03. 2005. These dwellings count for an average of 47.5% of the total housing stock in the European Union countries. At present in Slovakia, and also other countries of Central and Eastern Europe, there is a vast housing area which was built after the World War II. This is the matter of a complex of residential buildings that were built in the form of mass housing construction. Until the year 1990 the construction but also the renovation of residential buildings and housing developments was planned. After the year 1990 there was a change of socio-economical model of functioning of states of Middle and Eastern Europe. Changes were manifested in every area of life and in the area of housing politics they led to massive privatization of the housing fund localized in residential buildings in Slovakia for the prices which mostly did not correspond with the market value of sale of real estate. Privatization of the housing fund negatively affected its technical condition. Regular renovations ceased or were performed uncoordinatedly in parts depending on the financial situation and on ìthe level of awarenessî of the new owners. In Slovakia is in place a law on condominiums, which prescribe the establishment of a condominium in case of multi ownership. Owners can choose whether they establish a condominium in a multi-family residential building or close a management agreement with another natural person or legal person. Condominiums are until now important players in management of multifamily housing stock despite than in last few years started to increase the number of professional facility management companies. In former Czechoslovakia played an important role in construction and management of multifamily houses cooperatives. Their share on market was decrease in second half of 90¥s. The market share of cooperative before 1991 was 45% and in 2001 was 28.5%. Considering that the economy of Slovakia is not capable of replacing the existing housing fund which is located in the multifamily houses that were built after the World War II, it is necessary to dedicate an increased focus on renovation of this housing fund. The expenditures on multifamily housing stock refurbishment in last decades were comparing with the demand on a very low level. The main problems of the current multifamily housing stock in Slovakia are: need for modernization, low level of energy efficiency and insufficient building maintenance level. One of the options how to create sufficient sources for renovation of apartment buildings is to utilize the roof of the apartment building as a construction area and build it up. Means acquired from the sale of built-up after deducting the costs can be used for renovation. It is a matter of a one-time possibility which is limited by many factors that depend on localization and constructive technical solution of the apartment building. In Slovakia, in different parts of the country, there are around 4500-6500 multifamily houses which can be extended by one or two floors. Of course this is only a rough estimation which is based on the number of houses which are lower than 8 floors. Roof extension for multifamily houses is a good possibility to create additional dwellings close to the central part of cities without build up existing green spaces. Profit from the selling of new dwelling units is an ìextra sourceî to finance the reconstruction and modernization of multifamily houses. Roof extension in existing residential areas is a very complex issue and has positive and negative influence to the living space and living standards. Multifamily houses are situated in every European country. In the western and eastern part of Europe are problems joined with multifamily houses different scope. There is one element which is similar in every country and that is the energy saving potential after the refur bishment. To create additional apartments in existing living areas is a good possibility to make correction in existing structure of size of apartments. In current multifamily housing stock in Slovakia is the share of the flats with size 100 or more square meters very low compare with the Western Europe. This article is an outcome from international research project SuReFit ìSustainable Roof Extension Retrofit for High-Rise Social Housing in Europeî.