This project is for the upward extension of a family home between party walls, in Sabadell. The present building, on one of the streets connecting Sabadell with neighbouring towns, is 3.90 metres wide, with a depth of approximately 19 metres on the ground floor and 15 on the first. The occupants wanted to add on two bedrooms for the children, a guest room, a play area for the children and a utility room with clothes line.

In keeping with prevailing planning regulations, this extension takes the form of two new floors built around the staircase in the middle, which is the basis for the organisation of the existing spaces. This central area occupies the whole height of the extension, and organises the layout of the new elements. This allows daylight into the centre of the building, avoiding the darkness which would otherwise be inevitable in such a long, narrow construction. The spaces in this central area, to either side of the stairs, are the children's work and play areas.

The existing house presents a difference in level between the floors to either side of the entrance stairway, producing a very different combination in section of the new spaces from the conventional separation into storeys. Where the house opens onto the back garden (south side), a 4.75 metre high space is created to house the children's rooms. These two rooms are superposed one on top of the other in 2.30 metre high spaces, using a light flooring system of metal bars and fibreboard. The guest room - for occasional use only - and a small bathroom are laid out in the part overlooking the street (north side); above them, drawn back from the outer facade, is the utility area. A light metal stairway perpendicular to the building's main staircase leads from the children's area up to the utility room.

The various rooms are closed in by transparent or mobile elements in every case. The spaces are designed to fit together, shunning the idea of frontiers to enable the occupants to enjoy the new home in its entirety. The purpose is also to provide natural lighting everywhere and make it a pleasure to use this rather long, thin interior space. The soft colours of the walls, the use of fibreboard for the floor and the predominance of light-weight metal elements all go to give this new construction an overall atmosphere of airiness, warmth and light.