A historic building was erected 1895 and suffered severe damage during WWII. It was eventually used through more than 60years with exclusive appartements in the four lower floors and just-about repaired roof on top. Two flats were added, that both got the advantages of the view to the downtown skyline as well as the green courtyard on the other side. This 'closed' the urban gap and raised the roofline to the neighbor's height. Due to the structures age and abilities the addition was planned and carried out as a timber construction - this has massive ceilings (Austrian 'Kreuzlagenholz', crosswise laminated layers) to use the passive cooling abilities and gain better sound insulation.The local building regulations asked for all important parts of the structure to be 'REI90'-fireproof. This was achieved whilst still keeping the ceiling's massive abilities and needed a unique permit.All details of the design had to be coordinated with the 'Building Preservation' and several neighbors.The construction works took place while four stories underneath were used without any interruption.