Gypsum goes long distance

This article appeared in Form & Function, Issue 6, 1987

Gypsum goes long distance for phone company
Drywall & plaster provide for long-term needs without running up phone company's construction bill

Large office facilities can be difficult to design because of the need to deal with employee orientation and overwhelming scale, in addition to the usual office requirements. Such was the case in the design of the two-million sq. ft. administrative center of Pacific Bell in San Ramon, Calif. The need to provide a productive, comfortable and safe environment for over 7,000 employees made the project a major challenge for the architects, Skidmore, Owings & Merrill (San Francisco office). The resulting design took advantage of every available option, such as the beautiful open country surrounding the facility, and the abundant features of drywall, plaster and industrial gypsum products form United States Gypsum Co.

The new building represents a significant change for the employees of Pacific Bell. Instead of having locations in numerous San Francisco buildings, the company's new workplace is centralized in relatively open country about 25 miles east of San Francisco. The size of the site permitted the building to be large enough to combine many of the downtown facilities, but it created a whole series of design problems and opportunities for the architect.

"Our design takes the form of a three to four-story pinwheel," explained Edward D. McCrary, associate partner of Skidmore, Owings & Merrill. "We did this for several reasons. For one thing, we wanted to maintain a low profile to avoid disturbing the pleasant surroundings. That design also permitted us to cut the site into four quadrants, three of which provide parking close to the center of the wings. The fourth quadrant is occupied by and eleven-acre lake which provides an outdoor amenity, water for the building's cooling system and pleasant views from the employee dining facility also located in that quadrant. The ends of each wing are terraced to further lower the building profile.

"At the center of the building is the main entrance structure which contains conference rooms and other central facilities. This structure also provides access to the employee dining facility and to each of the four wings. Each wing also has a mid-point access, containing stairwells and elevators, form the parking areas. On two sides of the main entrance structure are attractive three-story atrium-lounges which also serve to separate the office wings from the general facilities in the main entrance structure," McCrary said.

"Besides providing maximum usable office space, locating the offices in long narrow wings also permits typical office spaces to be laid out in a way that allows employees to be within 60 - 70 ft. of windows. Thus employees can see the golden hills on either side of the valley. This also serves to help visually orient the employees so that they don't easily get lost or sense the large size of the office facility.

"The detailing of surfaces in offices, lounge spaces, conference rooms and dining areas was generally done in drywall because it offers the most economical treatment. Drywall also has the flexibility to allow us to provide the interesting detailing we wanted throughout the facility. However, some details were so complex that their surfaces had to be done in lath and plaster. Certain other surfaces, such as the hundreds of columns throughout the building, required a critical uniformity of surface and were repetitious enough to justify prefabricating them form cast gypsum. This product was also used to produce some dramatic planters that provide landscaping and appeal in the atrium spaces that function as employee lounges," the architect said.

All of the drywall and plaster applications were done using U. S. Gypsum products. The drywall and plaster applications were installed by Anning-Johnson Co., Burlingame, Calif. The cast-gypsum details were prefabricated by William Kreysler & Assoc. Inc., Petaluma, Calif.

"The Pacific Bell project had a critical completion schedule because the company wanted to take advantage of savings they could generate by eliminating short-term leases," said Brian Nesgoda of Anning-Johnson. "As a result, we were faced with a schedule crunch. We had to install over nine million sq. ft. of drywall in about two years. Plaster had originally been considered for much of this project. However, construction delays in the early going left too little time for the application of plaster, and when the change was made to drywall, we even had to find ways to speed that up. In many cases we used DURABOND 90 Joint Compound, which sets more quickly than conventional joint compounds, to allow us to finish taping and begin painting sooner.

"The time schedule was also a factor in using prefabricated column covers and other details. By having the column covers prefabricated from cast gypsum, we were able to insure uniformity in the finishes and speed the job along significantly. In the case of the planters in the employee lounges, the reveals in their surfaces would have been very difficult to create with lath and plaster. Thus we used the same prefabrication source to have these precast," Nesgoda said.

Cast gypsum saves time and cost
All the prefabricated cast gypsum details were created using HYDROCAL FGR Gypsum Cement from the Industrial Gypsum Division of U. S. Gypsum Co. This product was especially appropriate for these applications because its combination with glass-fiber matting permits intricate details to be made form very thin material. This technique reduces the weight and cost of the castings. Also, since the castings were fabricated offsite, they were made in advance of need, and thus saved time. The cast gypsum details also helped keep the jobsite clean, since there is no water or mess involved in their installation.

"The manufacturing process begins by putting a thin 'face coat' of HYDROCAL FGR Gypsum Cement in the mould," explained William Kreysler, president of William Kreysler & Assoc. Inc., the cast gypsum fabricator. "Next we lay a glass-fiber mat on top of the face coat and impregnate that with additional gypsum cement and fiber glass until we build up to the thickness we need. Depending on the size and shape of the casting, we may add foam stiffening ribs to it, and embed sheet metal anchors to fasten it to support members on the job.

"Castings made this way are especially accurate because the gypsum cement doesn't shrink. Since the material is a gypsum-based product, joints and defects can be covered with conventional joint-treatment products. Also, the material is noncombustible and doesn't give off noxious fumes in a fire as plastic moldings do. But most important is the fact that the material is strong enough that the casting can be made very thin. The typical hard-column cover used at Pacific Bell is about 3/16 in. thick and weighs only about 100 lbs. A comparably conventional cast-plaster piece would weigh about 1,000 lbs. The weight difference means that the pieces can be handled quickly and efficiently on the job and the cost of the pieces is relatively low," Kreysler said.

Because the Pacific Bell project used about 1,000 half-column covers, the Kreysler firm used steel moulds to make them. Steel is more accurate and durable for long funs. Two different diameters, 3 ft. 2 in. and 2 ft., and several lengths, averaging 10 ft., were made.

The eight atrium planters (four in each atrium-lounge) were more complicated to design and build because of their martini-glass shapes. The Kreysler firm built a one-eighth section of the planter from the plans and constructed a mould from that. Then, the only problem was to make sure that the cast pieces fit properly and could be attached precisely to the steel structure supporting the planters.

Drywall serves many functions
"Drywall is an economical material that permitted us to create relatively inexpensive details that have the interest and finish quality that the client wanted," continued McCrary. "One way to take advantage of the particular qualities of drywall was to create reveals using gypsum panels.

"In the atrium lounges, for instance, we used two paint colors and wide reveals to relate the color and lines of the precast concrete on the building's exterior. In virtually all other area of the building we used a pair of narrow reveals near the ceiling line. In the circular dining facility, we used several curved applications of gypsum panels, One detail in particular, however, a conical ceiling rising to a skylight, had to be formed in lath and plaster.

"A number of 2-hr. fire-rated partitions and shaft enclosures were constructed from drywall systems. Many of these were conventional mechanical shafts and core walls, however, we designed an unusual 2-hr. fire-rated design around stairwells. Rather than enclosing the stairs in the usual manner, we left them open to encourage their use by employees and treated the adjacent corridor as part of the fire-rated stair shaft. Thus the stair areas have automatic fire doors and the fir-rated corridor walls around them.

"Drywall systems also provided sound ratings for all offices. Rather than detailing to avoid flanking sound paths through acoustical ceilings, we used drywall ceilings and unbalanced drywall partitions around the offices to provide high sound-control integrity. Fabric panels on open-office sides of partitions and a sound-masking system were used to reduce noise levels in open-office areas," said McCrary.

All the 2-hr. fire-rated partitions were constructed using the USG Cavity Shaft Wall System. Even the 2-hr. corridor walls had this system. Structural members within these walls made application from both sides difficult and USG Cavity Shaft Wall is designed to be installed from one side only. Where office wings butt against other wings or the main entrance structure, shaft walls were constructed back to back, providing 4-hr. fire ratings.

Other drywall products used at Pacific Bell included 1/2-in. SHEETROCK Brand FIRECODE "C" Gypsum Panels, USG Metal Trims, DURABOND 90 Joint Compound, USG Ready-Mixed Joint Compounds and USG Ready-Mixed PLUS 3 Total Joint Compound. Plaster applications were done using metal lath and RED TOP Gypsum Plaster.

Pacific Bell San Ramon Valley Administrative Center, San Ramon, Calif.
Architect: SKIDMORE, OWINGS & MERRILL (San Francisco)
General Contractor: SWINERTON & WALBERG CO.
Cast Gypsum Fabricator: WILLIAM KREYSLER & ASSOC. INC.
Drywall & Plastering Contractor: ANNING-JOHNSON CO.

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Last updated: 09/21/06