San Francisco, CA
One California Street
One California, designed by Wellton Becket Associates, is a mid-century modern high rise featuring vertical runs of windows between columns clad with precast concrete panels. SGH performed a condition assessment of the precast panels and found corroding reinforcing was causing the concrete panels to crack and spall. We subsequently developed a facade rehabilitation program using a custom designed mortar to match the existing concrete.
Our field investigation included a visual survey, from the ground and a swing stage, and observations at exploratory openings. We tested concrete samples in our laboratory to determine the depth of carbonation and concluded carbonation allowed the embedded reinforcement to corrode.
SGH estimated repair quantities and developed construction documents for repairing and stabilizing the precast concrete panels. Our design included the following:
- Repairing cracks and spalls in the precast concrete panels with a custom repair mortar we designed to match the physical and visual properties of the existing concrete
- Applying a penetrating rust inhibitor to precast concrete surfaces to form a protective film around the reinforcing steel and help mitigate future corrosion
We provided construction administration services including overseeing mockups of concrete patching mortar samples to find the best match for the existing concrete, reviewing contractor submittals, responding to requests for information, visiting the site to observe ongoing repair work, and helping the contractor resolve field conditions.