CaixaForum - Madrid

The CaixaForum Madrid is built on a converted plot located at 36 Paseo del Prado Street, just opposite the Madrid botanical garden, in the capital of Spain.

Following the one built by Arata Isozaki in Barcelona in 2002, this new socio-cultural centre concept has instantly become a shining light in the Spanish capital. It is intended to be a public place for art exhibitions, musical performances, public meetings, and a hotbed of culture.

Its creators, Jacques Herzog and Pierre de Meuron,  had the ambition of making it an authentic "urban magnet", designed not only to attract art lovers but also the general population of the city and the many cosmopolitan visitors of this Madrid quarter near some of the most important Spaniard museums: Prado, Thyssen-Bornemisza, and Reina Sofia museums, and the Atocha train station built by the Pritzker prizer Raphael Moneo.

This new art centre, offering a surface area of 11,000 m², is located on the site of a former power station and an out-of-place fuel station. Although the classified brick walls of the power stations required a conversion in order to preserve them, the demolition of the garage was a stroke of fortune as it made it possible to clear a space for a small plaza in this very dense quarter, thus leaving some breathing space between the Paseo del Prado and the reconverted building.

Since its inauguration in February 2008, the CaixaForum immediately stimulated the interest and curiosity of the public, while its cultural calendar, despite its quality, was relegated to second place. Crowds of curious visitors, tourists, students, and art lovers, wander through the floors of the building, which is open from 10.00 am to 8.00 pm with access free of charge.

Dig, raise, caught in the middle
As the interior of the power station was too cramped to house all the functions set out in the programme, three solutions were established in order to enlarge it: dig, raise, or double up the existing building with a replica erected on the plaza, at the risk of filling it up and stifling the site once again.

Herzog and De Meuron chose and combined the first two, competing with both architectural and technical virtuosity.

In fact, the entire brickwork shell has been suspended; once it had been levitated, its stone base was placed around the entire periphery of the ground floor, thus clearing a covered space above and below, and thus splitting the project into two distinct parts. Excavated on two levels, the building basements and the open-air esplanade including the foyer, auditorium, service rooms, and car parks.

Their old windows were filled in, with openings made here and there for new geometric bays; the coated brickwalls shelter the lobby on the first level, and the music halls on the second and third.

Finally, a restaurant and offices take their place at the top of the building in a steel structure grafted to the top of these original walls. Adorned by its veil of rusted metal and flanked by a green wall – concealing the gable of an adjacent building closing off the plaza on one side – the CaixaForum Madrid, which is the result of a simple yet powerful urban gesture, quietly imposes its personality.

The opening created by the suspension, literally draws in visitors and those just passing through, in the covered square, leading them to the nearly-compact but elegant entrance to the museum and its steps leading in. This likeable space is, from one end to the other, a shelter from the unpleasant wintry weather and a place of shade in the summer.

Contrasting architecture
Herzog and De Meuron's design is full of contrasts. The initial visuals include a juxtaposition of the brickwork and green wall by Patrick Blanc, or even that of the sky with the rust of the rooftop. This rusted cladding (from panels of 800 x 800 x 10 mm), is delicately pressed in front of the full parts of the façades to provide solid material, and perforated in front of the glass parts so that natural light can pass through and create a different texture.

Then there are some environmental contrasts between the covered area and the lobby level, and between the flowing character of the exhibition galleries and the complex spatiality of the top floor in the walkways, offices, and restaurant.

Entering the restaurant is an emotional moment. Its south-east side exposes its glass vertical wall protected by rusted plates acting here like many moucharabiehs. This metallic filigree, cut into a pixelated framework representing maps of Spain and Portugal, filters the rays of sun and creates a soft lighting giving the place an almost feminine character.

The blue Jacobsen chairs and the silicone ceiling lights designed by Herzog and De Meuron complete the rest. In the evening, the visual effect is reversed: the interior lighting transforms the restaurant into an urban lighthouse while the light emanating from the covered square marks out the boundaries of the foot of the building and enhances its raised profile.

The top and down technique
The metamorphosis of the old power station started with a veritable surgical operation: its brick walls and overhanging steel superstructure were held in the air by means of three support mounts arranged in a triangle and which contain the vertical channels (lifts, freight lifts, and stairwells).

This superstructure, made up of a network of beams and shear walls form the brick shell reinforced by a brace. The building, detached from the ground by cutting out its base, appears to defy the laws of gravity, leaving engineers stunned by its audacious construction. The structures and foundations for the underground sections were carried out by means of traditional techniques.

Above ground level, suspended by eleven ties to the beams on the 2nd level, the lobby floor (L+1) is a bold design all on its own; this made it possible to remove the posts from the covered square and implement the polygonal underside making up the ceiling. It is a cleverly designed sandwich structure of variable thickness constituted by a composite assembly of which the 15 cm compression slab, the variable-height stiffeners, and the steel underside form an assembly of rigid interlinked caissons suspended from the ties.

The visible facing of the covered square is made up of 2 mm polygon sheets, fixed to the caissons and welded together. Their facets multiply the reflections of the metal and amplify the volume of this passage since its height is limited. This cladding, referred to here as a shell mould, continues into the stairs leading to the lobby, where it transitions into triangular plates creating a floor which also projects thousands of reflections and offers a feeling of softness beneath the feet.

The lobby interior reveals the structural mechanics of the suspension with its ties to the 2nd level floor and its steel HEM 700 composite beams coated with metal-grey paint. The technical ventilation, climatisation, and lighting equipment and structures are deliberately left visible.

The suspended ceiling is symbolically hinted at by means of a triangular framework of neon tubes, as if it was an illuminated art fixture. The dark-wood furniture of the welcome and cloakroom desks is suspended, in the image of the building, continuing with the levitation theme.

Exhibition levels
The exhibition levels are composed of two large open floor decks whose network of visible composite beams has been doubled up in order to cross the 21-metre span without interruption. The floors are composed of HEB 750 castellated beams spaced out in 3 metre intervals, laid at 916 mm and connected to a composite floor (PL 76/383/1 mm) topped with concrete to form a 20-cm thick slab. The lighting and ventilation fixtures are arranged methodically in the middle of each section.

From the third floor up, the brick walls of the power station are gradually phased out. So in order to complete the space required by the programme, a steel framework was added to hold the fourth floor, the façades, and the roof of the steel extension.

The latter was "sculpted" to remain in harmony with the urban skyline of the surrounding buildings and offer a space on the roof, cleared to make way for a small roof terrace.

Jacques Herzog and Pierre de Meuron have been involved in prestigious projects, but the style they adopted with the CaixaForum was not necessarily expected of them. They have impressed with their virtuosity in this difficult exercise of architectural grafting and the aptness of their structure. Their use of the vertical garden – very popular these days – appears to be completely essential to the project. We are very far from the pithy words of Corbusier who said to anyone who would listen, "ivy is the mayonnaise of architecture". Hats off to the Swiss!

(By Pierre Engel)