History and architecture of Casa Batlló

In 1903, Passeig de Gràcia had become the street where Barcelona's industrial bourgeoisie displayed their wealth. Fifty years earlier, the city walls had been torn down, and Ildefons Cerdà's plan had laid out the expansion district (Eixample) over the fields on the outskirts. This avenue, which connected the old city with the town of Gràcia, was its central axis. Owning a house there was not simply a real estate decision; it was a statement.

Josep Batlló i Casanovas, owner of textile factories, bought a building of rental apartments at number 43 that year. It was a typical building constructed in 1877 — some sources date it to 1875 — by Emili Sala Cortés, the architect for whom Gaudí had worked as a draftsman. It is often read that Sala was his teacher at the School of Architecture, but the dates do not support this: Sala graduated in 1876 and Gaudí in 1878. The oldest source that mentions the relationship, from 1927, states the opposite, that the young Gaudí worked for him. Batlló's intention was to demolish the house and build a new one. Gaudí proposed something else.

It's important to know who the client was, as it's often confused. Josep Batlló i Casanovas (1855-1934) was a manufacturer of silk fabrics, and he had no connection to the Can Batlló textile factory in Sants, which belonged to another branch of the family and is now a neighborhood facility. He was married to Amàlia Godó, daughter of one of the two brothers who founded La Vanguardia. Money from silk and a newspaper's last name, precisely when Passeig de Gràcia was becoming the city's showcase: commissioning a memorable facade was not an aesthetic whim, it was advertising.

The fact that the idea of demolition was not just a minor detail is demonstrated by the paperwork. In the municipal archive, dated October 26, 1904, there is a file opened for number 43 on Passeig de Gràcia, under a title that leaves no room for pleasant interpretations: "Demolish the house", meaning to tear down the house. The most visited renovation in Barcelona began, on paper, as a demolition.

The decision to preserve the building was not driven by conservationist ideals, but by practicality: the structure was sound, and demolition would be expensive. What Gaudí did was to empty it and rebuild it from the inside. He expanded the patios de luces to allow the interior to breathe, redistributed the floors, added two stories, and completely redesigned the facade and the roof. What remains of the Sala Cortés house is the basic structure, and little else of what can be seen.

The phrase was recorded by Josep Bayó, the master builder who carried out the renovation, and who years later recounted how the work was done in that house. Translated: "We will not do what was originally planned, so as not to diminish what is next to it." What was next to it was the Casa Amatller, completed four years earlier by Josep Puig i Cadafalch. Gaudí had something more striking in mind, but he toned it down out of respect for the neighbor; for the same reason, he moved the cross tower towards the center of the roof instead of placing it on the edge of the dividing wall, which is where it would have been visible from the entire street. The building thus contradicts the narrative of the block as a battleground between architects.

The construction work lasted from 1904 to 1906. The artisans who worked with him were the usual ones, the same ones who would later go to Casa Milà (La Pedrera): carpenters, blacksmiths, ceramicists, and stained-glass artists, at a time when an architect could still draw a door handle and have someone forge it that same week.

The image of the brilliant architect facing a stingy client doesn't fit this house. He got along so well with Batlló that it was Batlló himself who brought him the next client: Pere Milà i Camps commissioned Gaudí to design Casa Milà – La Pedrera – based on that recommendation, and the two houses eventually ended up less than five hundred meters apart, on the same side of the same street.

Where there was conflict was with the administration. The construction began without a permit, the City Council issued a suspension order that was not obeyed, and the file remained open while the house was completed, furnished, and filled with residents. The permit arrived six or seven years after the construction was finished, when there was nothing left to authorize. With Casa Batlló, shortly after, he would clash with the City Council again, this time due to excessive volume. It was his way of working: build first, argue about the paperwork later.

From the street across the way, the facade can be seen in three sections. At the bottom, the ground floor and the main level are made of Montjuïc sandstone, carved into bone-like shapes: columns that resemble femurs, windows with soft profiles, and a balcony that protrudes over the promenade. This is where the popular nickname, casa dels ossos (house of bones), comes from.

Above, the roof: a curved line of scale-shaped tiles that shift from green to blue and violet as they rise, topped by a ceramic spine. At one end stands a cylindrical tower with a four-armed cross, its arms pointing to the cardinal directions, and the initials of Jesus, Mary, and Joseph. The original cross was lost in the 1930s, and the current one is a replacement.

The second problem was the ventilation. In the attic, under the roof, there is a series of sixty catenary arches in white – the number is provided by the house itself – which support the roof without the need for beams: the same structural solution that Gaudí was testing at the time for the Sagrada Família, here applied to a laundry room and a storage space. And on the roof, the twenty-seven chimneys grouped into four sets are deliberately twisted so that the wind does not return the smoke inside.

The most widespread interpretation is that of Sant Jordi: the roof would be the dragon's back, the tower the knight's lance piercing it, the balconies the skulls of the victims, and the columns below their bones. It fits well, is told in all the tours, and is probably the first thing you will hear upon entering.

It's important to understand how that interpretation is supported. The official statement from the institution itself is that there is no evidence that the legend was depicted, and there is also no evidence to the contrary. Gaudí wrote nothing about it. It is a plausible interpretation, but not a documented fact.

At least two other styles are also present. The maritime style: the facade as a water surface, the interiors with shell and whirlpool shapes, and stained glass windows in marine tones. And the carnival style: the balconies as masks, and the entire house as a mask placed over a bland building, which, in a way, is exactly what happened. None of these styles exclude the others.

Today, it receives nearly two million visitors per year: 1,908,052 in 2024, according to the Barcelona Tourism Observatory. It is, after the Sagrada Família and Park Güell, the Gaudí work that receives the most visitors, and the one that has grown the fastest in the last decade.