The Powder Magazine's tile roof is typical of very early buildings, as are the 32-inch thick brick walls, which originally would not have had windows. The steep hip roof is punctuated by gables on all sides. The interior roof structure was constructed so that the building would implode were any explosions to occur inside. After a new magazine was built in 1748, this structure was condemned in 1770. Shortly thereafter, the outbreak of the Revolutionary War created a new demand for the old Magazine,
and it was again used to store powder. After 1820, the building was used for a variety of things including storage, a printing house, and livery stable.
Since 1902 the Powder Magazine has been owned by the South Carolina Society of Colonial Dames, which operates the property as a museum of early Charleston history. The building has recently undergone an extensive archaeological and architectural conservation effort led by the Historic Charleston Foundation.