City Hall Limestone Facade
Architectural cleaning and protective coating of a century-old historic limestone exterior, restoring its civic grandeur while preventing further deterioration from urban pollution, biological growth, and moisture intrusion.
The Need
A century of urban pollution, biological soiling, and failed 1970s-era sealers had severely darkened and degraded the building's historic Indiana limestone exterior.
Service Performed
Low-pressure soft washing, D/2 biological solution treatment, previous sealer stripping, and application of a breathable, reversible consolidant approved for historic masonry.
Timeline
8-day exterior project with scaffolding, executed to California Office of Historic Preservation standards during normal city operations.
The Challenge
The building carried State Historic Register designation, requiring all cleaning agents and coatings to be reversible and non-damaging to the original limestone. A 1970s acrylic sealer application had trapped moisture beneath the stone surface, accelerating spalling. Biological soiling (black crust, algae, and moss) had penetrated deeply into the porous limestone matrix over decades of neglect.
Our Stone Cleaning Process
Historic Assessment
Documentation, mortar analysis, and spot-testing determine safe cleaning methods and concentrations compliant with State Historic Preservation guidelines.
Biological Treatment
D/2 Biological Solution is applied to all affected areas, dwell-time managed to penetrate and kill biological growth at the root level without acid exposure.
Low-Pressure Wash
Gentle pressure-rinse at stone-safe PSI removes loosened soiling, old sealer residue, and biological material without impacting the parent limestone.
Breathable Consolidant
A vapor-permeable, reversible silane-siloxane consolidant is applied to strengthen the stone matrix and repel future moisture intrusion for 15+ years.
"For the first time in decades, the building looks the way it should. CATA respected the history of the structure in every decision they made."
— City Historic Preservation Officer, Santa Ana
Ready to start your project?
Get a custom estimate today and see the CATA difference.