St. Regis Hotel Tower/WilliamsBuilding Retrofit, San Francisco

The $180 million St. Regis Museum Tower project, which includes a new 42-story, 750,000-sq.-ft. concrete hotel and the retrofit of the adjacent, historic Williams Building, began in December 2001 and was recently completed.

The St. Regis Hotel includes 269 rooms and 102 luxury condominiums, as well as a four-level below grade parking garage for 161 cars. The structure also includes a three-story African American Cultural Museum.

"Webcor Builders approached the historic Williams Building rehabilitation with innovative building techniques, sensitivity to historical preservation, as well as with creative structural engineering solutions that created a feasibile integration of a historic building within a new complex mixed-use tower," said Jeff Snyder of San Francisco Museum Tower LLP/Carpenter & Co. "Webcor's experience with historical structures proved to be incredibly valuable as they anticipated unforeseen conditions before they actually presented themselves in the field. Webcor's proactive approach with the owner, architect and various engineers was collaborative and yielded stellar results with an end product that we're all proud of."

Webcor provided value to the owner on this project early during the preconstruction phase with several design alternatives. Webcor recommended a concrete frame for the building in place of the composite steel and concrete structure. In addition, the company reduced the basement floor-to-floor heights from 10 ft. to 8 ft., 4 in. These changes eliminated approximately $3 million in concrete and rebar costs from the project.

Additional structural savings were accomplished through many design changes on the project. Webcor removed all of the gravity beams in the tower and changed the design to flat plate. It also significantly reduced quantities of reinforcing in the mat, slabs, shotcrete walls, shear walls and other miscellaneous elements.

By assisting in the redesign of the core shear wall, allowing it to be installed ahead of the structure and detailed formsavers at the slab to wall intersection, Webcor enabled the slab to wall connection to be made when the slab was poured with relative ease. In addition, Webcor recommended a shoring system with slant piles rather than a slurry wall and were able to save the owner an additional $1 million.

Part of the project includes the historical renovation and seismic strengthening of the Williams Building, originally built in 1907. The Williams Building will house all of the St. Regis service areas, including health club and spa, food service, and operation offices. Webcor teamed with Skillings Ward Magnusen Barkshire to change the design, which resulted in the continued use of the existing structure by strengthening the vertical diaphragm above the floor rather than below it. This resulted in a net savings of $1.5 million for the owner.

The Williams Building is a nine-story steel frame building with brick aggregate, concrete floor slabs, and masonry cladding. The building suffered damage during the 1989 Loma Prieta earthquake. The structural concept of the seismic retrofit includes a new mat foundation in the basement, structural shear walls at all elevations and added topping slab concrete at each floor to strengthen the floor diaphragm. The retrofit required substantial structural demolition, including removal of the 9th level. The building is approximately 45,000 sq. ft.

Owner's Comments:

"Webcor's proactive approach with the owner, architect and various engineers was collaborative and yielded stellar results with an end product that we're all proud of." -Jeff Snyder, San Francisco Museum Tower LLP/Carpenter & Co.

Project Team:

Owner: SF Museum Tower LLP
Architect/engineer: Skidmore, Owings and Merrill
Construction manager: Webcor Builders (hotel)
Construction manager: T.M. Davis & Associates (Williams Building)
Program manager, general contractor: Webcor Builders
Key subcontractors:
Dees Hennessey
McGrath Steel
Peninsula Builder
Watertight Restoration
Webcor Concrete
Delucchi Sheetmetal

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