More sculpture than building, the Solomon R. Guggenheim Museum in New York City is what its creator Frank Lloyd wright called organic architecture. Entering this architectural spaceship is like walking into a giant concrete seashell.

The building was constructed of three types of concrete, all air-entrained and all made with a plasticizing admixture. Lightweight, expanded-shale concrete was used in the ramp and floors, while normal weight concrete was used in the bearing walls to ensure a smooth finish. Spiral exterior curtain walls which are supported on the outer edge of the spiral ramp were formed by shotcreting 5 inches of concrete from the inside of the building against carefully fabricated curved plywood forms. The inside surfaces of these walls were then furred, lathed and plastered, and the outside surfaces were smoothed and painted. All concrete was designed at 3500 psi; slump was kept at 3 to 4 inches.

Expansion joints were carefully omitted from the Guggenheim structure. The expanded helix, supported only at the columns, provides maximum freedom of movement. Except for the rigid connections between column and spiral where they meet at every floor, there are no connections between floors. The entire perimeter of each spiral revolution is thus free to expand or contract on its own, and the joints are not missed. The building expands laterally as much as 3/4 inch on a hot summer day.