Tate Modern has changed London since 2000. The impact it has had on urban design and the development of the South Bank and Southwark, has been as substantial as its influence on the city’s artistic, cultural and social life. The new development will add another decisive dimension to the architecture and environment of this quarter and beyond. With a new entrance to the South, and a direct North-South passage, taking people from the Thames through the existing building and the Turbine Hall out to a new city plaza to the South on Sumner Street and from there on to Southwark, the new development will connect Southwark with the Thames and provide much improved open, public space.

Tate Modern is the world’s most visited museum of modern and contemporary art. In its next stage of development the vision is to establish a new model for museums of modern and contemporary art, by fully integrating the display, learning and social functions of the museum, strengthening links between the museum, its locality and the city.

In close collaboration with the Tate, we carved a path through the jungle of unusually numerous parameters that must be taken into account. The resulting paths and connecting lines, gradually acquired shape, condensing into a pyramidal form generated from the combined geometries of the site context and existing building. The clover-shaped dramatic subterranean oil tanks are at the heart of these plans and they are a point of departure for the new building. When we converted the power station we dug out the Turbine Hall in order to turn the vast physical dimensions of the existing structure into a tangible reality. Here, the oil tanks form the foundation of the building as the new volume develops and rises out of the structure below. They are not merely the physical foundation of the new building, but also the starting point for intellectual and curatorial approaches which have changed to meet the needs of a contemporary museum at the beginning of the 21st century. These approaches require a range of gallery spaces, both larger and smaller, along with 'As Found' spaces of less conventional shape, and better facilities for the gallery’s popular learning programmes.

As well as doubling the gallery space, The Tate Modern Project will create a diverse collection of public spaces dedicated to relaxation and reflection, making and doing, group learning and private study. These spaces are spread over the building and linked by a generous public circulation system rising through the building. The vertical orientation of these spaces is clear in the same way that a horizontal orientation is evident in the first phase of the Tate Modern.

At the same time we felt it was important for the building to be visible from the North. As one approaches the Tate Modern from the river, the new Switch House can be seen rising behind the power station without competing with its iconic chimney. Integrating the new building into the existing urban fabric has been fundamental to the project, as well as integrating it into the skyline of the city and ensuring that visitors both inside and outside could orient themselves.

We wanted the combined elements of Tate Modern, old and new, to be expressed as a whole, we wanted to have them come together and function as a single organism. Using the same base palette of bricks and brickwork in a radical new way, we created a perforated brick screen through which light filters in during the day and through which the building will glow at night.

The brickwork also reacts to the inclined faces of the form by stepping to approximate a pure geometry. With both of these simple actions, texture and perforation, the brickwork is transformed from a solid and massive material to a veil that covers the concrete skeleton of the new building. The façade changes in appearance depending on the observer’s point of view, not just from transparent to opaque, but also in pattern and orientation. This continuous wrap of perforated brickwork is broken by the introduction of horizontal cuts to allow for views and provide daylight and natural ventilation to the internal spaces. The location of these 'cuts' is in direct relation to the internal programming and planning of the building. The result is a new yet symbiotic reading that is distinct and unique along the skyline of London.

Opening on 17 June 2016, the new Tate Modern will be a model for museums in the 21st century. Designed by internationally renowned architects Herzog & de Meuron, a spectacular new building will add 60% more space and will open up the museum to the area around it. It will be Britain’s most important new cultural building for almost 20 years, and will complete the site’s transformation into an accessible public forum.

Tate Modern changed London when it first opened in 2000. Herzog & de Meuron transformed the derelict Bankside Power Station into a home for the UK’s collection of international modern and contemporary art, sparking local regeneration and creating a new landmark on the Thames. The power station’s original Boiler House was converted into galleries, learning studios and social spaces, while its Turbine Hall was turned into a huge open space for special commissions and events. Tate Modern quickly became the world’s most popular museum of modern art, attracting around 5 million visitors each year – more than double the number for which it was designed – while its collection grew to encompass a huge variety of art from around the world.

2016 marks the next phase in Tate Modern’s evolution, with the opening of a new 10-storey building to the south of the Turbine Hall on the site of the power station’s former Switch House. The new Switch House building is rooted in the cylindrical underground Tanks, each measuring over 30 metres across and providing the world’s first museum spaces dedicated to live art, installation and film. They form the physical foundations of the Switch House and the conceptual starting point for it, offering new kinds of spaces for a new kind of museum. Above them are three additional floors of world-class galleries with a wide palette of volumes, from intimate small-scale environments to dramatic top-lit spaces. They are complemented by extensive areas dedicated to learning and interpretation, as well as a new restaurant, bar and Members Room, topped with a public terrace offering 360-degree panoramic views of London. A new bridge across the Turbine Hall joins the existing Boiler House galleries on Level 4 to the new Switch House galleries, uniting both sides with the Turbine Hall at its heart.

The Switch House arranges the new spaces into a unique pyramid-shaped tower, with its concrete structure folding into dramatic lines as it rises. Reinterpreting the power station’s brickwork in a radical new way, it is clad in a perforated lattice of 336,000 bricks. This unique façade allows light to filter in during the day and to glow out in the evening, transforming a solid, massive material into a veil that covers the concrete skeleton of the new building. Thin vertical windows in the new galleries echo those in the Boiler House, while also allowing visitors to look out over the landscape or across the Turbine Hall. As visitors journey up through the Switch House, long horizontal windows are also cut across the façade to offer new views and reveal details of the brickwork. The resulting exterior creates both an iconic addition to the skyline and a unified Tate Modern. It also puts environmental sustainability at the heart of its design, with a high thermal mass, natural ventilation, solar panels and new green spaces.

Reuniting the team who developed the original Tate Modern, Herzog & de Meuron have worked with Vogt Landscape Architects and designer Jasper Morrison. Two new public squares are being developed around the site, while the footprint of the Tanks is echoed in a large terrace opening out from the new southern entrance. Specially-selected furniture by Jasper Morrison will complete the interior of the building, responding to its varied architecture from the galleries and concourses to the restaurants and bars. Tate Modern will also host a free display of Morrison’s designs to mark the opening this summer, and a book about the building will be published this autumn, edited by Nicholas Serota and Chris Dercon and featuring interviews with Herzog & de Meuron, Günther Vogt and Jasper Morrison.