Number 16 Store the Powder House (Mo 42)

Number 16 Store, known as the Powder House, is a Grade II* listed powder magazine located in Morice Yard, Devonport, built in 1744. The structure is made of coursed rubble with brick dressings and features a vaulted roof that is not visible. It has a rectangular single-depth plan and is a single storey with a seven-bay range. The front is parapeted with brick corners, and the central three bays have brick pilasters leading to a raised parapet and a central pediment. There is a small 20th-century doorway and loops in the flanking bays, with 19th-century inserted casements on either side, also with brick dressings. The returns have blind round arches in projected full-height panels, with a round-arched doorway on the left. Above the central entrance is a notable gilded cartouche of the Duke of Montague.

Inside, the building is divided by brick baffle walls with five segmental-arched openings, smaller at each end, creating four bays with round-arched stone vaults. Each bay features a channelled timber beam extending from front to back, which is part of a former all-wood traveller. The walls are said to have a double skin designed to contain blast and maintain an even temperature.

Originally, the Powder House was designed with a surrounding wall intended to deflect blast, similar to the internal baffles. The Yard was laid out by the Board of Ordnance starting in 1720, and Lord Montague served as Master General of the Ordnance from 1739 to 1749. This building is the earliest surviving naval ordnance magazine and demonstrates how ordnance magazines were strategically located near dockyards before the establishment of Priddy's Hard in 1773 near Portsmouth. It holds significant historical importance as part of the best surviving naval ordnance yard in the country.