It is taking more than a leap of faith for a world religion to restore its historic temple near Chicago and protect the building’s complex precast cladding against rain, wind and ice for centuries to come. It also is relying on a team of consultants to research precast materials, gather up quartz aggregate and improve upon a 60-year-old concrete mix design.

Restoration contractors working for the National Spiritual Assembly of the Bahá’ís of the U.S., the temple owner, are one month ahead of schedule on an eight-year project to excavate around the building, install new drainage equipment, rebuild nine electronically-controlled fountains and replace 8,000 precast concrete panels along exterior steps, gardens and walkways. The project, in the second phase of a major rehabilitation that began in 1983, is estimated to cost $23 million by its completion in 2009.

Reinforced. New precast panels will replace deteriorated cladding in steps and gardens. (Photos by Tudor Hampton for ENR)

Few buildings in the world have such an unusual maintenance program as the Bahá’í temple in Wilmette, Ill. "The Bahá’ís want the building to be here for 1,000 years," says Robert F. Armbruster, president of program manager Armbruster Co. Inc., Glencoe, Ill.

During planning, structural consultant Wiss, Janney, Elstner Associates Inc., Northbrook, Ill., analyzed samples of the temple’s 60-year-old concrete cladding and improved on the mix by suggesting the addition of air-entraining agents and superplasticizers. These admixtures allow for increased endurance and workability, according to Paul Gaudette, a Wiss, Janney consultant based in the firm’s Chicago office. "With any architectural concrete, you can anticipate more handling of the concrete, which can lead to challenges in durability," he says.

The round-in-plan Bahá’í House of Worship, designed in 1917 by French-Canadian architect Louis Bourgeois and completed in 1953, is clad in precast concrete panels that hang on a structural steel frame. The white panels reveal an exposed, shimmering quartz aggregate. The lacy concrete rises into a bell shape to form a filigreed dome that drapes over the nine-sided, 167-ft-tall temple.

Approaching the temple are 1,000 precast steps arranged in nine pie-shaped sections, each radiating from the building’s nine entrances. The 104-ft-dia temple sits on seven acres of land, with nine gardens, each 33 ft in dia, surrounding it.

The owner in 1993 completed a $6-million project to rebuild a 95-ft-dia skylight and replace a 300-ft-long concrete cornice around the base of the building’s exterior dome. Today, temple workers are precasting new cladding for steps, gardens and walkways at a Wheeling, Ill.-based studio 14 miles from the jobsite.

Armbruster outfitted the space with $1.3 million in overhead cranes, formwork, portable mixers and other equipment for the Bahá’í-owned-and-operated shop. In addition to the 3,000 tons of rare quartz used in the restoration, the owner stockpiled an extra 5,000 tons. Crushing and screening is done at the studio.

The new concrete probably won’t last a millennium, so making it easily replaceable is the objective. Panels mount with stainless steel fasteners for corrosion control, while the forms can be used at least 50 times, according to Bob Joyce, president of local general contractor Quality Restorations Inc. In the future, "another contractor can use the same design mix, materials and forms," he says.