The growing development of the cutting work on the Guédelon construction site went hand in hand with the quarrying of increasingly hard sandstone as the working face progressed. The workers went from fifteen or twenty tools worn out daily to thirty or forty. From 2007, the quarried stone became so hard that it took four times longer to cut. It was therefore decided to alternate ferruginous sandstone with limestone from Donzy, 18 miles (30 km ) from Guédelon. This decision is consistent with the Middle Ages and the duotone of other reference monuments.