The well-known expression "form follows function" accompanies us for nearly 200 years. The form follows the function. Thus, the outer appearance of a construct should derive from the function. Equivalent to this, the function and also the purpose on the basis of the outward shape should be clearly legible. The sculptor Horatio Greenough first used the guiding principle in 1852 in connection with the organic principles of architecture. Shortly afterwards Louis Sullivan published the expression in his essay "The tall office building artistically considered": “It is the pervading law of all things organic and inorganic, of all things physical and metaphysical, of all things human and all things superhuman, of all true manifestation of the head, of the heart, of the soul, that the life is recognizable in its expression, that form ever follows function. This is the law” Contrary to Louis Sullivan, who, with this principle, sought no renunciation of ornamentation, the Austrian architect Adolf Loos in his 1908 work "Ornament und Verbrechen" (Ornament and Crime) used an antithetical interpretation of the notion: “I have made the following observation and have announced it to the world: The evolution of culture is synonymous with the removal of ornament from objects of daily use.” In Loos' point of view, even an oversized glass façade of a high-rise building, which is of no use, is an ornament. In turn, the Deutscher Werkbund propagated a factual approach based on functions and convenient use. The 1907-based Deutscher Werkbund and the 1919-based state Bauhaus, devoted themselves essentially to the same basic idea: functionalism and the new objectivity. This thesis does not directly deal with the term form follows function, but pursues the general question of form follows? From which, considerations, backgrounds, framework conditions, arguments, possibilities, limitations, commitments, etc. emerges an architectural approach and design in the inner-city area in the 21st century? Based on the example of an attic conversion, an attempt is made to show the limits and possibilities of creating living space. The paragraphs of the rules and regulations are the main limitation of the design task. Is the contemporary notion „form follows paragraph "? The attic is considered a useful extension of the living space. Is the function of living, which should arise from the needs and demands of the user, recognizable by its appearance? The thesis is divided in two parts. The first theoretical part deals with the development of the Vienna Building Code and the currently relevant and valid regulations for an attic conversion. The second part deals with the status analysis of the chosen Gründerzeit house and the practical application of the theoretical first part. From the guiding idea, to concept development to the design task and finally to the elaboration of a submission plan. The concept should ultimately answer the question as to whether the restrictions of the regulations actually also mean a restriction for the creation of new living space regarding attics.