Ministry Of Defence Building Numbers L176 (Boiler House) And L177

The Boiler House, part of the Royal Gunpowder Factory, was built in 1857 and is constructed of yellow brick in English bond with a central skylight beneath a hipped slate roof. It has a rectangular plan and is a single storey building measuring six by three bays. The structure features a chamfered brick plinth and a dentil cornice, with paired brick corner pilasters. The east and west elevations are divided into three bays with a 2:2:2 window arrangement. The west elevation has segmental gauged red brick arches over 20th-century windows, which were originally sash windows with rectangular blind panels below. The rear (east) elevation has similar arches over blind windows, while the north side has three blind windows with a mid-20th-century entry inserted. The south side features two cast-iron windows flanking mid-20th-century sliding double doors, all adorned with radiating glazing bars above the arches.

A lean-to roof structure for the Dynamo House, built in 1902, is added to the center of the east elevation and is made of brick with a slate roof. Inside, the building has iron roof trusses supported by decorative cast-iron compression members. The Boiler House was constructed alongside Building L168, the Engine House and Mechanic's Shop, to provide power for the earliest steam-powered incorporating mills on the site, which have since been demolished. Originally, the Boiler House had a chimney at its northeast end. The addition of the Dynamo House likely indicates a transition from steam to electric power, coinciding with the change in function of the incorporating mill to cordite reeling.