This multi-family housing building is located in Príncipe Real in Lisbon and was built in 1757, 2 years after the 9.0 Richter-scale earthquake. Our client wanted to renovate the upper floor flat - simplify its layout and adjust it to the life of a modern family - while respecting the building’s constructive logic and the spirit and scale of the historic district. The roof’s apex defines the border between the living room - with a horizontal window overlooking the garden - and the bedrooms - with dormer windows. Bathrooms, kitchen and larder are grouped in an irregular-shape volume that differentiates spaces and uses in an easy, informal fashion, without doors or corridors. The materials - limestone, solid wood and plaster - are taken from the original apartment but their combination and design are boldly modern. The horizontal window is as wide as the apartment and is composed of 3 filters - glass, translucent glass and sliding shutters – that assure shading and privacy and echo the intermittence and texture of the windows in the lower floors.