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Two Union Square

A unique “fractal” stone pattern

Two Union Square

Seattle, WA

©Chris J. Roberts Photography

Architect: NBBJ

Client: Synergism Stone

Completion: 2019
Category: Special Project

Project Type: Stone Engineering
Stone Type: Travertine

Nov 2019–Architect Magazine

Jun 2020–

Jan 2021–Best of 2020: Architecture with natural stone

Two Union Square is one of Seattle’s elite business addresses. The remodeling of the common area includes a unique projecting “fractal” stone pattern requiring special attention.

The work of art derives its force from the abstraction with which the forces of the earth are represented here: the “fault” is formed with prisms, tetrahedra and irregular pyramids that are somewhat reminiscent of mountains and valleys. But high and low are only hinted at and do not grow into real mountain ranges or valley incisions. The travertine on the wall comes from the quarries of Tivoli in Italy. It is also a material whose surface enhances the expression of wild nature.

PICCO Engineering’s technical expertise in stone engineering facilitated BIM modeling for stone fabrication. PICCO also supplied shop drawings and designed the stone connections. Since each individual element has its own geometry within the tectonic fault, exact specifications were required not only for cutting. There were also detailed instructions for the installation, as the elements are anchored to the wall behind and to their neighbours. 

This unusual wall design shows the strength of natural stone: if the elements had been made of concrete or artificial stone, for example, casting and cutting would have been very expensive. But with CNC planning and direct implementation by wire saw, this can be done quickly and cost-effectively.

A total of 1,650 stone slabs were used for the cladding on the third floor. In the tectonic fault they are between 3 and 8 cm thick (1¼ to 3¼ inches). 

On the one hand, visible joints were needed to emphasize the geometry of the individual elements; on the other hand, they were not allowed to interrupt the homogeneity of the rock landscape.

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