The building, consisting of two floors and a pitched roof, is located on a plot of land where the direct sunlight is exposed from the rear façade. As it sits in the middle of a row of buildings, its main entrance is on Rua Castro Matoso. Since its construction until the present intervention, the building has always been used as a dwelling and has not undergone any significant modification or maintenance work, either on the outside or inside, which is why it had several pathologies, particularly in terms of the roof structure. In terms of the interior spaces, it was deemed necessary to overhaul all the technical infrastructure in order to provide the dwellings with the necessary living conditions. The remaining interior construction elements were mostly in good condition, with only finishing work and the dimensional adaptation of some spaces to the proposed programme being necessary. As the preservation of the building was a priority, a new wooden roof was proposed, over which the necessary insulation and cladding was applied, with the external cladding material being corrugated metal sheeting. This option was based on the desire to emphasise the difference between the cladding materials used in the extension and the construction methodologies between the “new” and the “old”.