San Francisco, CA
Bellaire Tower, also known as the “Jewel”, sits 20 stories high on top of Russian Hill in San Francisco, CA. Built in 1930, Bellaire Tower was designed by architect H.C. Baumann, a prolific San Francisco architect who designed over 400 apartment buildings and hotels. The tower was one of the first residential high-rise buildings in San Francisco constructed to new seismic codes after an earthquake struck in 1906. Abiding by these new building codes allowed Bellaire Tower to hold strong through the 1989 Loma Prieta earthquake.
Problems That Led To Repair
Bellaire Tower is home to many affluent residents however over the past two decades it has become infamous for the most water leaks of any building in the Bay Area. The leaks occurred mostly around the windows and repeated attempts of recoating left over 90 mills of non-breathable coating on the beguiling exterior. ‘Dress’ beads of sealant were also applied in failed attempts to correct the leaks. Furthermore, concrete spalling posed a safety hazard in addition to unappealing exterior inconsistent with a luxurious building. The columns and beams are framed with structural steel while the floor slabs and exterior walls are constructed of reinforced concrete. The exterior wall is 80,000 sf with 640 windows. The Art Deco exterior consists of a Portland cement parge finish with ornate columns and arches. As highlighted in the images above, most of the spalling occurring around the windows where leakage occurred and was caused by corrosion of the steel window flanges embedded within the surrounding concrete. Joints and cracks that came about due to corrosion of the reinforcing steel within the exterior wall were a potential source for leaking and spalling in the walls.
Sika Product Solution
The planning department insisted on keeping the original appearance of the building and restoring the elaborate ornamental features while protecting the building from future damage. Moving cracks were routed and sealed with a polyurethane sealant, Sikaflex® 1a. Reinforcing steel was coated with an epoxy-cement coating, Sika Armatec® 110. Spall repairs were either hand-applied or formed and poured with polymer-modified repair mortars, SikaTop® 123+ and SikaRepair® 223. Sikacrete® 211 and SikaGrout® 212 were used to protect the steel window flanges and select areas of the reinforcing steel near the windows. On the north and east elevations, some windows had to be removed and replaced without refurbishment as they were beyond repair. After the windows were addressed, the exterior walls were power washed and coated with an elastomeric, breathable, waterproof coating, Sikagard® 550W.