Located within feet of the San Andreas Fault, the un-reinforced walls of the Mission are over 30 feet high. This masonry construction is susceptible to damage or failure during earthquakes. Concern is focused on all the Missions due not only to possible loss of these historical structures, but also for the safety of our visitors, including Fourth Graders who visit to study the history of the California Missions.
A project like the preservation of Mission San Juan Bautista requires a Historical Structures Report to detail the repairs, conservation measures and upgrades needed to preserve the historic structure. This report was completed by the Architectural Resources Group, Inc. of San Francisco from work by experts in Geology, Hydrology, Structural, Mechanical and Plumbing, and Electrical Engineering. The History and Archaeology report was submitted by Dr. Ruben Mendoza of CSU Monterey Bay. Assistance is also being provided by engineering and construction experts who worked on the restoration of the Royal Presidio Chapel in Monterey, Mission San Carlos Borromeo in Carmel, and Mission San Antonio de Padua.
High priority deterioration issues found by the report are:
~ Repair and strengthening measures are necessary to improve seismic resistance.
~ To correct deterioration from lack of waterproofing, roof underlayments need replacement, there are many broken tiles, rotted roof timbers, and flashing details require repair and improvement.
~ Cement plaster throughout the church and museum is accelerating damage from moisture intrusion because it doesn’t allow the adobe to breathe. This must be replaced and the walls refinished with lime.
~ Windows and doors need repairing to prevent the intrusion of water.
~ Drainage systems need to be installed or improved to prevent the deterioration of the adobe walls.
~ Plumbing, electrical and mechanical systems all need upgrading.
~ The stone cemetery wall shows erosion and loss of mortar with vegetation growing out of stone and adobe masonry joints, which indicates surface drainage from the cemetery through the wall is uncontrolled.