The iconic buildings and structures of Stanford University were constructed of a locally sourced sandstone quarried south of San Jose. Over time, this sandstone becomes stained from environmental particulates, biological growth, and pedestrian use. As an on-going cleaning and maintenance program, PMR was contracted to perform the overall cleaning and associated masonry repairs to the Stanford Main Quad East Gate and sandstone balustrade.
Prior to the actual work, cleaning methods and products were developed as test panels to be reviewed by the client. To prevent accelerated deterioration of the soft sandstone, the approved cleaning method consisted of warm water low-pressure power washing in conjunction with areas of acute staining to be removed by fiber brush agitation. Use of a gentle biocide was also selectively applied to slow the reoccurrence of biological growth. In addition to general cleaning, several locations of loose and deteriorated masonry units were both patched to match adjacent sandstone and stabilized by pinning to adjacent masonry units.