The works have been under almost constant restoration from the late 14th century onwards, with particularly notable schemes occurring in 1402, 1481, 1483–1499 (overseen by Alesso Baldovinetti, who was made "official restorer of the mosaic decoration"), 1781–1782 (general cleaning), 1821–1823 (dealing with serious damage in the area of "Stories of Noah") and 1898–1907 (massive reintegration).