 As the previous roof truss system was somewhat plain, Renwick devised a system that still relied on timber, but left an exposed ceiling with the decorated and varnished timbers visible.He also added a Spanish Renaissance-style bell tower which was not unique in the US; older Spanish mission churches in the west already had bell towers.The exposed bell had become a symbol of the Spanish mission, and that fact influenced the decision to build a bell tower in the Cathedral of St. Augustine.