The 2201 Westlake/Enso building in Seattle combines residential condominiums, retail space, and office space into one building through an innovative structural design. The building uses a combination of post-tensioned slabs, high-strength concrete and reinforcement, and minimal interior columns to accommodate four different uses stacked vertically. This structural solution allowed for open floor plans while keeping construction costs within budget.

1. 2201 Westlake/Enso

2. Location: Seattle, WA
Submitted by: Cary Kopczynski & Co.
Owner: Vulcan Real Estate
Architect(s): Callison Architecture
Engineer(s): Cary Kopczynski & Co.
Contractor(s): Sellen Construction
PT Supplier(s): PTC
2201 Westlake/Enso

3. Project Highlights:
• Creative structural solution where the use of post-tensioning directly
led to the success of this mixed-use project.
• Design accommodated four different uses (parking, retail, office, and
residential) stacked vertically in the building without column offsets
and transfers.
• Used an innovative combination of PT and high-strength concrete
and reinforcement.
• The long-span PT design facilitated the minimal use of interior
columns and construction of the curved exterior façade
2201 Westlake/Enso

4. Project Overview:
For the first time in one building, 2201 Westlake/Enso combines high-
strength 100 ksi reinforcing steel with an ultra-long span floor system
using a drophead design at the core. The building marries high-end
condominiums with long-span office space, spacious ground-level retail,
and user- friendly subterranean parking. It is a true mixed-use building—
the structure is the result of innovative solutions applied to a complex
design program.
2201 Westlake/Enso is a cast-in-place concrete structure featuring
concrete shear walls and a combination of one- and two-way post-
tensioned slabs. The structural frame was selected to satisfy the
architectural layout without compromising the owner’s vision for open
and spacious floor plans for office, retail, residential, and parking use. In
addition, the combination of structural systems kept construction costs in
line with the project budget and delivery objectives.
2201 Westlake/Enso

5. 2201 Westlake/Enso
Project Overview Continued:
The building incorporated many exceptional structural features as
follows:
• Long post-tensioned spans throughout;
• Cantilever beam to lengthen post-tensioned slab spans;
• Subterranean post-tensioned slab shrinkage control;
• Open loading dock with post-tensioned girders;
• High-strength reinforcing bars;
• Seismic core efficiency; and
• Outstanding exterior façade