“Located on Russian Hill, 945 Green Street is one of the most iconic residential buildings in San Francisco, CA. After almost 100 years in service, the 14-story building was beginning to show major signs of deterioration, including spalling, cracking, and exterior delamination.”
…several options for repair were considered, ranging from chipping and patching to full-depth removal and replacement. Ultimately, the chosen method consisted of the use of sacrificial cathodic anodes; polymer-modified, vertical repair mortars; and a vapor-permeable membrane to coat the entire exterior. The anodes were used in the patches as well as in some areas of sound concrete to prevent future corrosion issues.
As the restoration work began, any exposed steel was covered in an anti-carbonation coating and an anode was attached when the steel was more than 3 in. (76 mm) from the concrete surface. Then, the patch was filled with polymer-modified cementitious repair mortar containing a penetrating corrosion inhibitor. As the patching mortar was being applied, the contractor was also overseeing the repair and replacement of the architectural details. The first area to be restored was the line of 20 decorative columns between the 11th and 12th floor panels. Only one column had a capital and footer, so a foam mold was created with a profile of the detail. The mold was then used to recreate this detail for the other 19 columns. Around the outside of the building there had been busts of a woman’s head and, like the panels/columns, most were missing. One bust was found in decent condition so, after minor repairs to the original, a mold was created and the remaining busts were cast using a pre-bagged, self-consolidating concrete mixture.
The building received a topically applied penetrating corrosion inhibitor on all bare concrete. After allowing the inhibitor to penetrate the surface and onto the steel, the remaining surfactant was removed using a power washer. Finally, for added waterproofing and long-term protection, the entire building was coated with a high-performance elastomeric wall coating system.“