One Sansome Street Building

The One Sansome Street Building is a Postmodernist skyscraper designed by William L. Pereira, and built between 1983 and 1984 in San Francisco, CA.

One Sansome Street Building is not the only name you might know this building by though. It is common for companies to want to attach their names to iconic buildings when they move in, or for the general public to come up with nicknames, and this one is no exception. The One Sansome Street Building is also known, or has been known as, Citicorp Center, or CitiGroup Building.

Its precise street address is 1 Sansome Street, San Francisco, CA. You can also find it on the map here.

The construction of the skyscraper incorporated parts of the Holbrook building that housed the Anglo and London Paris National Bank, which occupied the site from 1910 to 1981. This historic corner atrium, known as the Conservatory, has been integrated into the One Sansome Building and transformed into a luxurious lounge.

William L. Pereira was the architecture firm in charge of the architectural design.

The One Sansome Street Building can be categorized as a Postmodernist building.

The One Sansome Street Building was completed in 1984. At that time Postmodernism was the prevailing style. Fresh, bold and daring, architects were exploring the freedom of designing without having to follow the strict, sometimes arbitrary rules of a specific architectural movement (which ironically became a movement itself). The One Sansome Street Building was therefore every much in line with what the architecture community, and the people liked and wanted at the time.

The One Sansome Street Building uses a framed tube-in-tube structure , with steel columns and concrete slabs.

A framed tube-in-tube structure uses a central core, known as inner tube, which usually holds stairs, lifts and installations, and a perimeter of columns around it, which form the exterior tube. The interior tube is tipically more massive (often made of reinforced concrete), and the exterior tube is "lighter" (made of steel or concrete columns). Both tubes are conencted via horizontal elements which make up the floors and also transmit any horizontal froces from the facade to the core.

The facade of the building is load bearing. This is a direct consequence of the integration of the exterior "tube" into the facade, something which most framed tube-in-tube buildings do in order to liberate the interior space from structural elements and achieve a more flexible interior.

So the facade of the builing is techinically load-bearing, yes, however, in between the load-bearing colums we find a modular type of facade, which by itself would not be cosnidered load-bearing.

From an aesthetic point of view, the facade features a combination of glass and gray granite with rounded corners.