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Portfolio: Project Details

Coit Tower
Historic Restoration and Rehabilitation
San Francisco, CA
Coit Tower, the beloved San Francisco landmark, is one of the City's most architecturally significant public buildings, known for its controversial seven-story towering design, its prominent placement on historic Telegraph Hill in 1933, and for its series of Diego Rivera-inspired frescoes depicting "Life in California" on the interior walls.

Aside from routine maintenance, Coit Tower had received little conservation attention during its first fifty years. In the mid 1970's, the City and County of San Francisco, concerned about continuing deterioration and spalling of the concrete surface and its inability to stop water penetration from damaging the murals and frescoes in the lobby, attempted unsuccessfully to patch deteriorated exterior concrete and to arrest the leaks by installing additional layers of roofing material, only to further exacerbate the leakage because of trapped water. In 1984, the City decided to work with expert consultants to correct the spalling and water problems and save the murals, and hired Interactive Resources to investigate the landmark, document the extent and causes of deterioration, and restore the tower to its original condition.

Our investigation included a field survey of the walls, retaining walls, planters, sidewalks, and stairways associated with the monument. We found advanced deterioration due to the harsh marine environment and inadequate concrete cover.  We recorded this deterioration in the form of sketches and photographs, which were later presented in a detailed report.

Cracks occurred at a variety of locations throughout the tower, which were both unattractive and a potential source of further deterioration if not properly repaired. Spalling was another serious problem; corroded reinforcement and delaminated concrete were fully exposed.

On the basis of our report, the City decided to move forward with complete restoration plans for the tower. We developed a program to restore the integrity and beauty of the structure and stop water infiltration into the tower lobby. New materials were carefully specified to duplicate the original materials in strength, composition, color, and texture.

An unusual aspect of the project was the controversy over the monument's surface coating. There were many local and State agencies involved in the restoration approval process, each of which held varying opinions as to whether the new coating should duplicate the color and texture of the tower at its original 1933 appearance, or to give it the "weathered look" characteristic of the existing condition. A series of samples of the of the existing coating were taken from various parts of the monument, and analyzed for color, porosity, and reflectance, and consensus was reached on the issues of color and texture. The selected coating also had to be physically compatible with the existing material. After many hours of investigation and research, and numerous presentations to the various agencies, the "perfect" surface coating was found.

The restoration work on the exterior of the tower was completed in November 1988. An Art Conservator completed restoration of the murals early in 1989, and the tower was reopened on July 18, 1990 to the public following the installation of protective barriers.

Coit Tower is heavily visited year round and is very important to the City's tourism industry; therefore, we developed a plan that enabled the landmark to remain open throughout most of the entire restoration.