The Casting Shed was attached to the base of the furnace. When the molten iron had pooled at the bottom, workers in the casting house "tapped" the furnace by knocking out a clay plug. The iron then ran out into channels in the sand floor made with shovels by the workers. As it oozed over the sand, the iron made a noise like a pig, thus the name "pig iron."

Today, only a portion of the Casting Shed's stone foundation still remain at the site.