It constitutes a personal interpretation of the housing concept inherited by Le Corbusier. The houses are organised on two levels, with independent accesses. On both floors, a small central distributor gives access to all rooms. Downstairs there is the living room, dining room, kitchen, a bedroom and the restroom areas. The rest of the bedrooms are upstairs, plus a gallery that surrounds the living room and leads to the small balcony in the corner. The organisation in duplex housing is reflected in the façade, which alters the conventional scale and proposes a more dignified image of urban housing.

The building is located in a corner in the upper area of Barcelona and is made up of a total of six duplex apartments, with a double-height space in the living room. The choice of the duplex, which was an innovative typological solution at that time, allowed the surface area of the housing passageways to be reduced. Inside the building we find all kinds of technical artifacts, such as garbage collection tubes, elevators with double cabins (elevator and freight elevator), goods lifts, etc., which express the machinist tendency of the building. Thanks to the loose dimensions of the houses, Sert was able to explore with great intensity the expressive possibilities of Le Corbusier's purist language, to the point that this building can be considered one of the most significant of its time. On the façade that faces Muntaner Street, the interior distribution of the duplexes is expressed, through the alternation of windows, terraces and balconies; on the other hand, on the façade facing Párroco Ubach Street, the balconies are repeated from top to bottom. The first two bays that face Muntaner Street are made of a metallic structure; the others are made of load-bearing walls. The stucco walls are painted in grey and pale green (Bauhaus green), the steel tubes are white, the metal windows are dark grey, and the lower part of the building is clad with glass panels, painted on their interior sides.

Built between 1930 and 1931 by Josep Lluís Sert, with the collaboration of Sixte Illescas i Mirosa, this block of duplex housing on Muntaner Street is one of the most significant works of the Catalan and Spanish rationalist movement.

This residential building known as Josefa López Houses is located in the Sant Gervasi neighbourhood of Barcelona, in a block of houses framed by Tavern, Muntaner and Rector Ubach Streets. The property stands specifically on the corner of Rector Ubach (nr. 21) and Muntaner Streets (nr. 342-348).

The property is developed on a plot of 18 x 17 m while occupying a built surface of 1520 m² with a very regular quadrangular plan and distributed in eight levels. The building consists of six floors for housing, a higher level for studies and the doorman’s house; a ground floor intended for shops, a garage for tenants and a basement.

The basement level takes up half a floor and is intended for heating services, elevator machinery, supply counters and storage. This plant also leads to the garbage pipes that can be taken out on Rector Ubach Street from a separate staircase.

On the ground floor - towards the side of Muntaner Street - there are two shops, the entrance to the estate and the garage, which communicates with the staircase through a separate door. On this floor the lobby of the property with two well-defined sections is also located; the first is configured as the proper access from the street to the building and the second houses the gate, the neighbours' staircase and the elevator.

Through the elevator or the neighbour's staircase you access each of the homes in the estate, with the characteristic that there are two floors per landing of stairs but with the entrance every two landings since each home occupies two overlapping half floors.

The original structure of these duplex homes was described in AC Magazine in 1931 and despite the refurbishments carried out in some properties - which have been divided into two apartments - part of the distribution of the primitive architectural project is still maintained.

One of the most relevant characteristics of the spatial configuration of these homes is precisely their duplex configuration. This model was presented in the 30s of the 20th century as an innovative proposal and alternative to the consolidated type in the Eixample, with elongated houses that extended from the main façade to that of the block’s patio. In this building, on the other hand, the six duplex homes allow for a vertical spatial organisation that allowed the corridor of the house and the ventilation shafts of the interior rooms to be removed. Instead, the architects designed two 2x7m halls; an upper one for the private use of the tenant and the service, and a lower one that was the main entrance to the house.

Given the particular and private character of this building, the description of its interiors is complicated, beyond the access to some of the recently modified and segregated homes. It is for this reason that we offer a description of the spaces as they were in the 1930s and that, to a certain extent, they have remained on some floors.

On the floor plan, two zones that communicate vertically through a staircase located in the living room are distinguished. Thus, we find the night area facing Rector Ubach Street and which houses the bedrooms, while the area open to Muntaner Street houses the living room with the kitchen, the dining room and a master bedroom.

The aforementioned hall was originally located on the ground floor of each house, which gave way to the living room and which through some doors folding could be incorporated into the dining room that was located on this same level. The living room has a double height with a gallery or mezzanine next to Muntaner Street and a staircase on the opposite side that internally connects the two floors of the house.

On the upper floor of each house (those that still retain the original structure) there is a bedroom with a bathroom (for guests), a service bedroom with a toilet and an office that communicates with the hall, the dining room and the kitchen. Also, on this floor there are three main bedrooms, one of them with a gallery on Muntaner Street and another service bedroom. The latter and the ironing room opened into the hall on this upper floor and had an exit through it and independently, towards the staircase.

The upper level of the property is occupied by some houses that in the original project were known as "study floor" and where the terrace was located, on which they had the upper floors, since they were located above the living rooms.

One of the most emblematic elements of the building is precisely the façade, both that of Muntaner Street and that of Rector Ubach. With the simplicity that characterised the rationalist movement, it presents an external arrangement which is a consequence of the interior distribution.

The two pediments are finished with stuccoed surfaces, in pale green, that emphasise the geometric rigor of the composition and contrast with the white of the tubular irons and the dark grey of the metal carpentry of the windows. These windows (of the standard "Fenestre Cristall" house) are configured as some of the most characteristic elements of the Modern Movement, due to their horizontal component and the boat-style design of the railings.

On the Muntaner Street façade, horizontal windows (four corresponding to the living room, dining room and two apartments) alternate with the gallery of the bedrooms and the small balcony on the living room mezzanine. On the Rector Ubach Street façade, the corner balconies are the extension of the room's mezzanine, giving the beams better support and facilitating the external cleaning of the room's large windows, fixed for reasons of economy.

Built between 1930 and 1931 by Josep Lluís Sert, with the collaboration of Sixt Illescas i Mirosa, this duplex apartment on Muntaner Street is one of the most significant works of the Catalan and Spanish rationalist movement.

This building was commissioned by his mother, Jenara López Díaz de Quijano, as rental apartments; that is why it is known as "Jenara López Apartments" or "Josefa López Apartments", due to a transcription error. One of the studios on the top floor was also the residence of Josep Lluís Sert until 1939, when he went into exile.

We are facing a fundamental work - together with the house at Via Augusta 61 by Rodríguez Arias - in the fullness of the methodological and linguistic orthodoxy of rationalism, which can be considered as the first mature work of Spanish rationalism and being the first residential building resolved from the duplex system.

Structured on a duplex floor, it represents one of the most original typological contributions of the GATCPAC, creating a strong contrast between the modernity of this work and the classicist eclecticism of many of the existing buildings in this sector of the Eixample.

One of the most relevant characteristics of the building is precisely its duplex configuration. This system was a novelty at the time for a residential building and made it possible to reduce the corridors of the dwellings, which were dark and poorly lit, in favour of two levels and halls that organise the spaces. Other novelties related to the supply of services to homes were also introduced, such as the garbage collection pipes and the elevator with a double cabin (elevator and freight elevator).

In 1975 it was restored and given a remarkable revaluation, despite the changes to the attics and the shops on the ground floor. Currently some of the homes are renovated and segregated.