Roof top extensions for multifamily houses in SlovakiaIn the countries of the European Union with the exception of Malta, approximately 100.1 million multifamily dwelling units are situated. These dwellings count for an average of 47.5% of the total housing stock in European Union countries. At present in Slovakia and also other countries of Central and Eastern Europe, there are vast housing areas which were built after World War II. Slovakia's multifamily housing stock was privatized during the 1990s. 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 World War II, it is necessary to place an increased emphasis on the renovation of this housing fund. The expenditures for the refurbishment of multifamily housing stock in recent decades, when compared with the demand, have been at a very low level. The main problems involving the current multifamily housing stock in Slovakia are: the need for modernization, the low level of energy efficiency, and the insufficient level of building maintenance. One of the options for creating sufficient sources for the renovation of apartment buildings is to utilize the roofs of apartment buildings as construction areas for building additional floors (over - roofing). The means acquired from the sale of the new floors 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 the localization and constructive technical solutions for apartment buildings.This article is an outcome of the SuReFit "Sustainable Roof Extension Retrofit for High-Rise Social Housing in Europe" international research project.