The Amazon Spheres


General Contractor: Sellen Construction
Sector: Commercial
Region: USA
Business: Structural
Service: Steel Fabrication, Steel Installation
Date: 2016
Tonnage: 650 tons
Location: Seattle, Washington

Supreme Steel (formerly Canron) was selected for the fabrication and erection to build the Spheres project in 2013. Supreme’s team installed the last Catalan section in March 2016. The completion of this iconic project is a culmination of many hours spent collaborating with the architects, engineers, detailers, office and shop staff, and outside vendors.

The fabrication processes were adapted to fit this unique structure by utilizing laser tracking equipment to set up the jigs within 1/32 of an inch without a single dimension on the shop drawings. The detailers used a combination of 3-D modeling software (Rhino, Solid Works & AutoCAD) to create a model. The information from this model was linked to the laser tracking equipment and used to check each shop and field connection point.

An Architecturally Exposed Structural Steel (AESS) finish was required on all assemblies which entailed an extreme amount of grinding, sanding and the use of bondo on some of the joints. Each assembly was over width ranging from 17′-7 to 23′-10 requiring special overnight permitted loads with 2 pilot cars and 2 police escorts for each load.

Field assembly of the project used similar equipment to ensure proper placement of the assemblies into the final structure.


  • A total of 24,960 individual pieces were installed, and thanks to the tight tolerances achieved in the fabrication, only required a total of three shims, shortening the erection time by more than one third. Because of the tight tolerances achieved in the fabrication, the assemblies fit together so well that only 3 shims were used on the entire project and shortened the erection duration by more than one third.

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