The Castillo de San Marcos has been under assault since its construction started back in 1672. Aside from attacks by cannon and musket fire, the fort has also been battling Florida’s destructive climate, including powerful hurricanes and tornadoes, unrelenting heat and humidity, and corrosive salt air. In addition, inappropriate repairs have occurred utilizing modern day cements, such as Portland, which are chemically and physically incompatible with the original coquina stone. For these reasons, combined with the 3,500 visitors storming through on a busy day, the Castillo de San Marcos has been steadily deteriorating.
The horizontal surfaces, in particular, have suffered damage to a level that requires immediate attention. Individual coquina stones have disintegrated and mortar joints have failed. This has resulted in the surface becoming irregular and has created 'battle scars' where water collects and vegetation takes hold. The NPS Historic Preservation Training Center (HPTC), park staff, Southeast Regional Office, and the State of Florida Historic Preservation Office worked together to draw up a battle plan to stabilize the Castillo, one of our nation’s greatest treasures. The preservation crew inspected all of the coquina which comprises the top level of the inner and outer fort walls. Poor condition stone was replaced with healthy coquina. In addition, any previous repairs made with modern cements were carefully removed and replaced with historically accurate lime mortars.
It is important to note that the work was not performed to improve the visual appearance of the fort. Coquina stones were only replaced in cases where it was absolutely necessary in order to preserve and protect the Castillo de San Marcos for future generations. The deteriorated coquina was replaced by stone taken from a location near where the fort’s original coquina was quarried. In addition, compatible lime mortar was used for the bedding, pointing, and finishing of the stones.